Geotechnical characterisation and 2D soil cross-section model development in the Kashmir Basin

Abstract

An integrated analysis of the surface geology with geotechnical parameters of soils within the Kashmir Basin has been presented in this study. Spatial distribution maps of soil properties were prepared using an extensive database of Standard Penetration Test (SPT) reports at ~ 700 sites collected from geotechnical consultancies. The SPT N is high (~ 10–50) in the stiff, dry Pleistocene Karewas and low (< 20) in saturated Recent Alluvial deposits of the Jhelum River. These sedimentary deposits show a low plasticity index (< 17%) as well as the presence of stable clay minerals. The compression index is lower for Karewas (0.08–0.27) than for alluvium (0.16–0.36) indicating higher settlement hazard in the latter. Geological-cum-geotechnical cross-sections along seven transverse and five longitudinal transects were also developed. As an application of this study, the bearing capacity estimates, along with the liquefaction susceptibility map of the soils in the urban area of Greater Srinagar are presented. The alluvial floodplains are revealed to be critical in terms of low ultimate bearing capacity (< 300 kPa) as well as high liquefaction susceptibility (L_S > 0.8). On the other hand, Karewas show good bearing capacity (> 300 kPa) and medium liquefaction susceptibility (L_S 0.5–0.8). Based on these geotechnical aspects, Karewa highlands were found to be the most suitable for the expansion of the city and its future urbanisation. The results of this study are aimed to assist civil engineers in the proper design of structures, especially foundations, as well as to support urban planners in creating policies for town planning and expansion strategies in Kashmir.

 Introduction

Kashmir Basin is situated in the Himalayan region which originated from the collision of the Indian plate with the Eurasian plate about 50 Ma ago (Searle et al. 1987; Thakur and Rawat 1992). Himalayas extend in an NW–SE arc for over 2400 km length along which the Indian plate is still moving northward and thrusting under the Eurasian plate. Kashmir Basin is an NW–SE oriented valley about 140 km long and 50 km wide, bounded by Zanskar range on the north and Pir Panjal range on the south. Maps showing the Kashmir Basin superimposed over the topographic relief and digital eleveation model prepared in ArcGIS software are presented in Fig. 1a, b. Srinagar City, which is also the summer capital of Kashmir, is witnessing a sprawl of urban expansion continuing without proper planning (Kuchay and Bhat 2014; Nengroo et al. 2017). Greater Srinagar has an area of ~ 766 sq. km shaped through an expansion of the Srinagar city limits (~ 416 sq. km) beyond its boundaries into the adjoining districts of Ganderbal, Baramulla, Bandipora, Pulwama, and Budgam (Fig. 1). The concept of the Greater Srinagar area was proposed in the Master Plan-2035 for the Srinagar Metropolitan Region (Town Planning Organisation of Kashmir Region 2017). The unprecedented population growth followed by migration of people from rural countryside to compact urban centres along highways has been observed to increase by manifolds in recent years. In this context, it becomes imperative to understand and evaluate the geotechnical characteristics of soils in the Kashmir Basin to assist in the proper planning and urbanisation of the growing cities. The characteristics of soils in an area are closely associated with the geomorphology as well as the climatic conditions of the region. Since soils form the basic part of civil engineering constructions, especially in foundation design, the correct estimation of the properties is important. Civil engineering structures like buildings, bridges, dams, roads and highways, and tunnels require appropriate foundation systems within the earth. Site investigation for the evaluation of the geotechnical properties of soils is the first step in the design process of the foundations of the proposed structures, to prevent any failure in the future.

Fig. 1

a Study area showing the Kashmir valley superimposed over the topographic contours. Greater Srinagar boundary is also marked for reference in dark blue. Light blue lines represent the rivers and waterbodies draining the region. b DEM image of Kashmir region showing location and distribution of Karewa deposits (light blue shade) and the hypothetical topographic divide through the centre of the valley. Blue lines represent rivers draining the region

This study includes the exhaustive collection of standard penetration test (SPT) reports from local consultancies, to extract the various geotechnical properties of the soils at selected depths for the Kashmir Basin. The spatial distribution of the soil types and properties over the region has been discussed in the form of maps and histograms, in addition to their variation with depth. Longitudinal and transverse cross-sections have also been created for the basin in this study presenting a useful blend of geological information and geotechnical engineering, which is mostly neglected in civil engineering constructions. Considering the complexity of the Kashmir Basin in terms of its tectonic setup as well as its geological setting, the amalgamation of geology with geotechnical engineering is necessary for the successful design of structures. This study of the geotechnical soil properties at a regional level involving a link with the geology of the region, offers a first-of-a-kind insight into the Kashmir Basin since most of the earlier studies have either been purely geological (Dar et al. 2014) or purely geotechnical (Mir 2015; Khan and Shah 2016). Zahoor and Mir (2021) published a concise report on the types and properties of soils and rocks found in Jammu and Kashmir, which does not, however, provide a regional variation of the geotechnical properties of the soils. The lack of a proper geotechnical study at a regional level for the Kashmir Basin forms the motivation of this extensive study. To demonstrate the significance of this study, an application of the outcomes to urban planning and development of the Greater Srinagar metropolitan within the Kashmir Basin has been conducted by estimating the bearing capacity and liquefaction susceptibility of the soil deposits. From the perspective of geotechnical suitability, zones for preferred construction and development in the metropolitan region have been identified, and subsequent recommendations have been included. The geotechnical and geoengineering maps developed for the study area will serve as an initial guide for the planning of the expansion of the cities and the selection of proper foundations or ground improvement techniques at any site. To carry out the detailed design of a structure at any location in the region, the maps may be used as a source of general information on soil properties, requiring further detailed field and laboratory investigations.

To ensure sustainable economic development and urban growth, several factors need to be given adequate attention, especially the intricacies of the Kashmir Basin in terms of its complex geomorphology, fragile ecology, patterns of existing land use and transportation layout, as well as susceptibility to disasters including floods, earthquakes, and landslides. Earlier studies on urban sprawl in Srinagar City have addressed its socioeconomic and environmental impacts (Kuchay and Bhat 2014; Nengroo et al. 2017). The Master Plan-2035 also addresses issues of urban sprawl in the Greater Srinagar metropolitan and has provided a Land Suitability Map for the planned growth of the city by giving consideration to certain factors. The planners have duly included aspects like flood vulnerability, geomorphology like wetlands, lakes, and hills, elevation and slope, and land use of the area. Nevertheless, due to the absence of relevant studies, engineering aspects like geotechnical soil properties and information on geology are missing in the Master Plan. The current study endeavours to bridge the technical gap and furnish some of these beneficial missing links for the progress of the infrastructural development work in the region. This will possibly open pathways for merging outputs from microzonation research efforts with the town planning strategies in the region. The study may thus find its application in seismic microzonation studies for Kashmir which requires soil parameters as one of the chief inputs. Bearing capacity and liquefaction susceptibility maps developed in this study can be used as layers in GIS to develop zones for the region in microzonation studies.

Material and methodology

Figure 2 includes a flow chart to illustrate the methodology followed in this study and the acquired outcomes. The purpose is to combine geotechnical and geological data for the Kashmir Basin and highlight its importance for urban planning and development in the region.

Fig. 2

Flow chart illustrating the methodology followed for this study and the forms of outcomes obtained

Geotechnical characterisation of the Kashmir Basin

Geotechnical data based on laboratory tests conducted in various civil engineering projects at different sites in the Kashmir Basin was collected from various consultancy agencies especially the National Institute of Technology Srinagar (NITS), Space Engineers Consortium Ltd. (SECL), and Road Research and Materials Testing Laboratory (RRMTL). The database includes information on standard penetration test (SPT) results as per IS code (BIS 1981a), water table depth observations, and basic laboratory tests for index and engineering properties of soils at each site as per IS code guidelines (BIS 1983). The example of datasheets at a few sites from the consultancies is presented in the supplementary material. The data is available at a total of about 600–700 sites with the borehole depth varying between 10 and 30 m, thus giving a fairly good idea about the distribution of surficial soils in the valley. The compiled data, in combination with field observations, form the knowledge base for the geotechnical characterisation of the sediments of the Kashmir Basin. Parameters like soil classification, bulk unit weight (γ_b), moisture content, SPT N value, consistency limits (liquid limit and plastic limit), shear strength parameters (c and ϕ), and grain size distribution (GSD) for soils at each site were studied. As an application of this geotechnical study, the bearing capacity and liquefaction susceptibility of soils in the Greater Srinagar metropolitan have been estimated.

The parameters at each of the 700 sites have been plotted in ArcGIS software and interpolated to develop maps showing the spatial distribution over the Kashmir Basin. Since most of the dwellings and urban constructions are concentrated in the basin portion of the Kashmir region, the majority of the consultancy data is, therefore, also available for the sedimentary deposits which fill this area. Since the data is sparse in the rest of the region, the interpolation has been restricted to the central basin portion in which the data points are concentrated. The spatial distribution of the soil properties is studied, and an attempt is made in this study to correlate the soil properties with the observed geology and topography of the region.

Geology and geomorphology of the Kashmir Basin

The Kashmir Himalayas is composed of several mountain ranges delineating numerous drainage basins in the region (Fig. 1). The Kashmir Nappe Zone is an asymmetrical synclinorium flanked by the Panjal Thrust and the Zanskar thrust, with the oldest stratigraphic basement floor composed of the Precambrian Salkhala series and the Dogra slates (Wadia 1975). Overlying this basement is the synclinal basin comprising an almost complete sequence of Palaeozoic and Triassic marine deposits in the Kashmir Basin, formed by the Panjal volcanics (Panjal trap and Agglomeratic slate) and Triassic limestone. The bedrock of the valley thus comprises rocks like limestone, shale, andesites, slates, quartzites, siltstones, and dolomites (Ahmad et al. 2015). Kashmir region comprises complex landforms including mountains, hills, ridges, valleys and plains, which are a product of the tectonic activity in the region (Yeats et al. 1992). The elevation of the mountain ranges rises to as high as 4000–5000 m a.m.s.l. along the boundary of the Kashmir region. Towards the central region represented by the topographic depression hosting the Jhelum basin, the elevations decrease to around 1500–1600 m a.m.s.l. It is worth mentioning that the topographic slope increases abruptly towards the north from the valley floor, whereas it increases gently towards the south. In the SW portion of the basin represented by Budgam, Kupwara, Pulwama, Shopian, and Kulgam districts, the contours are wide apart signifying a gentle slope. The gentle slopes in these areas are basically tablelands/highlands of Karewa deposits reaching up to heights of 300–400 m above the regional elevation (~ 1900 m above sea level) near the topographic divide. These are a part of the long gentle slopes which ultimately lead to the exposed rocks in the high-rising Pir Panjal. In the northern part of the study area, elevation contours are closely spaced representing the high mountains that are a part of Zanskar range and the Great Himalayan range.

Development of the Kashmir Basin has been governed mainly by interrelated tectonic, climatic, and erosional (river incision, glaciation) processes (Dar et al. 2015). The geological succession of the Kashmir region has been explained in detail in several earlier studies (Wadia 1975; Ahmad et al. 2015; Bhatt 1976). The Kashmir Basin is filled with sediments brought down from surrounding mountain ranges by rivers and by the action of gravity. The maximum thickness of soft soil sediments is found at the centre with decreasing thickness towards the edges. Various boreholes drilled by the Oil and Natural Gas Commission (ONGC), the State Directorate of Geology and the Mining (DGM), and the Central Ground Water Board (CGWB) have failed to reach the basement (Mukhtar 2008). The sediments covering the basement are mainly of two types—Plio-Pleistocene sediments (older alluvium), known as Karewas, and the Holocene sediments, known as recent alluvium, overlying the Karewas. The geological map of the Kashmir region and the surrounding areas presented in Fig. 3a shows the detailed distribution of sediments (Karewa and Alluvium) in the Kashmir Basin along with the surrounding exposed rocks in the region. Karewas are fluvio-lacustrine sediments covering a huge area of about 5000 sq. km in the valley (Wadia 1931). These are unconsolidated and partially consolidated remnants of the sediments of the ancient Karewa Lake (Godwin-Austen 1864; Lydekker 1876), which once filled the valley basin and was later drained out due to major tectonic and geomorphic changes (Dar et al. 2014). The thickness of these sediments varies from the valley floor to the mountain edges; the aggregate thickness is estimated to be about 1300 m (Burbank and Johnson 1982; Kotlia 1985) or about 2000–3000 m (Mukhtar 2008). Karewas have been classified into two divisions—Lower and Upper Karewas—which have been further divided into various members (Farooqi and Desai 1974; Singh 1982; Bhat 1982). Upper Karewas consist of conglomerates, laminated silts, clays, sands, gravels, pebbles, and boulders (Roy 1975), whereas Lower Karewas are comparatively fine-grained, comprising mostly of stiff clays, with some amount of sand, pebble beds, gravels, and occasional lignite seams. Layers of volcanic ash are also found within these deposits (Burbank and Johnson 1982). The Karewas have been further grouped into Hirpur, Nagum, and Dilpur Formations (Bhatt 1976). Hirpur Formation is the oldest in geological succession and consists of clays, sandy clays, fine to coarse grained sands, conglomerates, lignite, and lignitic clays; Nagum Formation includes fine to coarse grained sands, sandy clays, marls, and gravels; and Dilpur Formation which forms the uppermost and youngest layer consists mostly of silts. The top layer overlying the Karewas is formed from the more recent (Holocene) alluvial sediments brought down by the rivers in the valley.

Fig. 3

Geological map of a Kashmir Basin and surrounding areas (modified after Thakur and Rawat 1992; Dar et al. 2014) and b the Greater Srinagar region developed in this study

The uplifting of Pir Panjal due to greater seismic activity has raised the southwestern flank of the valley. Subsequently, sediments from the mountains got deposited in the valley portion followed by inundation of the region under the retained water. This environment led to the development of fluvial-lacustrine Karewas. The raised southwestern flank is composed of Karewas whereas the valley depression has river alluvium. The clear division between the topographic rise composed of Karewas and the topographic depression composed of alluvium can be observed on the ground along the Srinagar-Sopore highway which runs parallel to the axis of the valley. The topographic divide represents a clear division between the predominantly Karewa deposits on the southern flank and the alluvium deposits on the northern flank of the basin (Fig. 1b).

Recent alluvium is, in general, contributed by processes involving glacial, fluvial, and colluvial activities (Mukhtar 2008). Glacial soils comprise boulders, gravels, and sand; flood outwash from Jhelum and other river systems consist of sand, silt, and clay; and colluvial deposits brought down from the surrounding hills and mountain ranges comprise of sands, pebbles, gravels, and boulders. The other types of soils predominantly found are mountainous soils which are composed of gravel and cobbles in a silt–clay matrix. Hill slopes and foothills have deposits of colluvial soils brought down through the process of landslides under the action of gravity and erosion. Fractured, weathered, and jointed rocks are exposed in hard rock terrain in the mountain ranges. The rivers and their associated tributaries represent an essential source of sediments for the valley portion and play an important role in the ever-changing dynamics of the basin. Jhelum is the major river flowing through the centre of the valley right across Srinagar in a north-westerly direction with major dwellings developed in its flood plains. Baramulla Gorge at the northwestern end of the valley is the only exit for Jhelum (Nakazawa et al. 1975). The Jhelum River, along with its tributaries drains the topographically depressed area of the Kashmir region and is thus the major contributor of alluvial soils in the region. In addition to the Jhelum River, lakes like Dal, Wular, and Anchar occupy a major area and influence the formation of soft lacustrine soils in their vicinity. These water bodies keep the complete stretch of alluvium water-saturated and soft.

Greater Srinagar metropolitan

The geological succession in Srinagar region specifically is available in several studies like Raina and Kapoor (1964) and included in Mazari (1975). In this study, a detailed geological map of the Greater Srinagar metropolitan has been prepared by utilising the information available in the literature, primarily from Mukhtar (2008), and supported by observations in the field and study of Google Earth images. The geological map is presented in Fig. 3b along with the major rivers and lakes draining the area. The northeastern portion of the Greater Srinagar is a part of the Dachigam basin in the mountainous tract of the Zanskar range. Bren spur/hills, Zabarwan hills, and Zewan spur surround Dal from northeast to southeast. Outcrops of the mountains rise in the form of small hills within the city up to a height of 100–200 m (1700–1800 m a.m.s.l), the most significant of which are the Sulaiman/Shankaracharya and Hariparbat/Koh-i-Maran hillocks (Fig. 3b). Most of the area is flat at the centre of the study area. Several low-lying areas (elevation 1582 above m.s.l) are present, which include Parimpora, Qamarwari, Bemina, Bhaghat, Barzulla, Rawalpora, and Natipora. These were earlier a part of the flood absorption basin and were hence marshy. In recent times, these areas have been reclaimed for construction purposes; however, soft soils and flood-like conditions due to drainage issues are still a problem in these areas. Highlands consisting of Karewas are located near Zainakote (1600 m a.m.s.l), Pampore (1600 m a.m.s.l), Budgam (1655 m a.m.s.l), and Soura-Buchpora (1600 m a.m.s.l) area. The maximum depth to the water table in Srinagar varies from 1.75 to 6 m bgl (CGWB 2013).

Fine-grained recent alluvium present in the low-lying, flat portion of the region merges with the mountains and hills with deposits like conglomerates, sand, boulders, pebbles, and cobbles in the transition zone. The floodplains of the river Jhelum are filled with recent alluvium consisting of fine sand, silt, and clay in the low-lying central region of Srinagar. Alluvium in the Sindh floodplain is mostly sand, followed by thick gravel deposits. At higher elevations, like in Harwan and Chandpora, coarser deposits of sand and gravel are deposited by the Harwan stream. Karewas abut the hard rock areas of the Dachigam basin. Upper Karewa exposures are present in the form of a strip of an elevated mound in the north-eastern part of Greater Srinagar bounded by Anchar in the west and Dal in the east (Bhat 2017). This area includes places like Gasu, Burzahama, Inderhama, Dhanihoma, Shuhama, Alasteng, Pandach, Gulab bagh, and Hodura in Ganderbal; and Bren, Wanihama, Batpora, Habak, Malshai bagh, Zukura, Umerhair, Hafizbagh, Wontabawan, Soura, and Nowshera in Srinagar. These top beds have been identified to be the part of the Dilpur member of the Nagum formation (Bhat 1982). The south-western flank of Kashmir represented by the long gentle slope of Pir Panjal towards the valley floor has significant deposits of Karewa. Thereby, Budgam in Greater Srinagar shows flat elevated tablelands of Karewa as shown in Fig. 3b. Karewa deposits are also found in some portions of Bandipora and Ganderbal districts in the NW portion of Greater Srinagar (Thakur and Rawat 1992; Mir and Mir 2019).

Results

Spatial distribution of water table depth

The water table depth map for the sediments in Kashmir Basin as well as Greater Srinagar metropolitan based on the observations in the borelogs is presented in Fig. 4a, b, respectively. The effect of the topographic divide is clearly discernible in the overall properties and behaviour of the soil in the region. Areas in the low-lying topographic depression of the valley are filled with saturated alluvium drained by Jhelum river and the major lakes like Dal, Anchar, and Wular. Water table depth in the alluvium deposits in the basin is shallow, mostly < 5 m. The depth of the water table increases in the hilly regions as is clearly observed from the spatial distribution maps. Karewas being uplifted on the southwestern flank, show deeper depths of the water table. The depth increases abruptly on the northwestern flank to over 30 m whereas, on the southwestern end, the depth increases progressively, ranging between 10 and over 30 m, following the trend of gradually increasing slopes. Clearly, the Soura-Buchpora Karewa, Pampore Karewa, and Budgam Karewa all show deep water table depths. The other regions filled with alluvium along the banks of Jhelum, Sindh, and Dhoodhganga have shallow water table.

Fig. 4

Spatial distribution of water table depth a in the Kashmir Basin and b Greater Srinagar region as observed in the bore logs

Geotechnical properties

Uncorrected SPT N values

Based on the results of laboratory tests collected from the technical reports, the soils of Kashmir Basin have been classified according to the Unified Soil Classification System (USCS). The grain size analyses, Atterberg/consistency limits, and physical investigation of soils conducted in each project were utilised for this purpose. In higher reaches where the slope is high, the streams and rivers transport great sediment load owing to their high energy and velocity. As a result, only large sediments like boulders and cobbles are deposited in the mountainous regions, mixed with coarse sand and gravels. Sonmarg, Pahalgam, Gantamula, and Aharbal show such types of alluvium. As the slope decreases, the energy also reduces, and therefore, the soil particles change to gravels and coarse sand. Kangan (Ganderbal), Chandpora (Srinagar), Harwan (Srinagar), Kalaroos (Kupwara), Nikas (Pulwama), Chehlan (Kulgam), and Anantnag are some examples of areas that are covered with coarse alluvium. The SPT N value is very high in these soils, and often refusal is encountered at a shallow depth of 1–2 m. On the other hand, the alluvium in the low-lying regions in the Jhelum floodplains is soft, unconsolidated, and saturated with water. This results in very low SPT N values (< 10) in these deposits. The soil is mostly fine-grained (silty or clayey) with > 70–90% fines (passing 75 micron sieve). This is because the river carries only fine particles due to the low energy in its final stages in the flat valley portion. Fine to medium sand is encountered at some depths, especially along the banks of Jhelum. Many areas of Srinagar and Sopore are covered with this fine alluvium.

The Karewa soils, on the other hand, are stiff, comparatively highly consolidated, dry deposits with medium to high SPT N values. Figure 5 shows the map of SPT N for the Kashmir Basin. The high stiffness, density, and strength of dry Karewa deposits may be a result of the consolidation over the thousands of years of its formation, i.e., the age effect. Another important factor may be the presence of calcium which could be the cause of cementation in the deposits. A large concentration of calcium (~ 603–1811 ppm) and magnesium (~ 133–261 ppm) has been found in the Karewa sediments, probably due to the contribution from the rocks in the surrounding mountains (Mukhtar 2008). The dissolution of limestone and weathering of rocks like Basalts, Shales, Phyllites, and Agglomeratic slates lead to the release of calcium into the water which has ultimately seeped into the surrounding Karewa formations over thousands of years. Within the Karewas, the soil type varies with location. Towards the valley floor, the predominant soil type in Karewas is found to be silt and clay with seams of dense sand continuing up to complete borehole depths. At deeper depths, gravel deposits are found. Towards the higher reaches, the depth of the fine-grained Karewa is shallow and is followed by gravel from around 3–5 m depths. The soils have high strength when dry; however, significant issues like slope stability failures and foundation issues have been reported in the Karewas throughout the valley when saturated with water during the wet season. SPT N follows the same trend as water table depth. It is higher in the peripheral regions consisting of Karewas and mountainous soils, whereas in the alluvial belt, the values are very low. Further, with respect to the depth at a single location, the SPT N value tends to increase due to the consolidation of soils at deeper depths.

Fig. 5

Spatial distribution of SPT N value in the Kashmir Basin at a 3 m, b 6 m, c 10 m, d 15 m, and e 20 m depths

Validation of geotechnical data with geophysical testing

For validating the geotechnical data collected in this study, the SPT N values have been compared with the shear wave velocity (V_S) estimates from our earlier study (Zahoor et al. 2023a). Borelogs at selected locations such as in Karewa deposits, floodplains, coarse alluvium, and foothills are illustrated in Fig. 6 along with the value of SPT N at certain depths as well as V_S. Figure 7a, b shows the spatial distribution of 30 m average velocity V_S,30 and that of N value (N₃₀) over the Greater Srinagar metropolitan. The figures reveal that V_S values obtained from geophysical testing are in good agreement with the geotechnical properties of the soils. Soils in the flood plains have very low V_S,30 and N₃₀ which indicates that they are soft and weak. High values are observed in sites in hills and mountains indicating their stiff and competent nature. Moderately high V_S,30 and N₃₀ are found in foothills and Karewa deposits.

Fig. 6

Borelogs with SPT N values and shear wave velocity profiles with depth for selected locations in different geological deposits

Fig. 7

Spatial distribution maps of a N₃₀ and b V_S,30 for the Greater Srinagar region

Consistency limits

Consistency limits, also known as Atterberg’s limits are determined only for the fine portion of the soil passing through 75-micron sieve size (IS code) using Casagrande’s apparatus. The distribution of the liquid limit (LL) and plasticity index (PI) of the fine grained soil in the Kashmir Basin is shown in Fig. 8a, b, respectively. It is observed that the region predominantly consists of soils with low liquid limit values (< 35%) such that these can be characterised as low compressibility soils as per Unified as well as Indian soil classification systems (USCS, ISCS). Some of the areas in the central portion, however, show deposits with a liquid limit of 35–50, thus behaving as intermediate compressibility (ISCS) or low plasticity (USCS) soils. Only a few sites show soils with high compressibility (LL > 50%). The plasticity index (PI) of most of the sedimentary deposits falls between 7 and 17% such that the soils have mostly intermediate plasticity. Other regions have low plasticity (PI < 7%) soils, mostly consisting of sands with zero plasticity. These low values of LL and PI indicate that the plasticity characteristics do not pose a severe threat to the construction practices in the region. The soils do not possess any extreme swelling or shrinkage characteristics that may need any special attention.

Fig. 8

Spatial distribution map of a liquid limit (LL) and b plasticity index (PI) of soils, and shear strength parameters c cohesion, c, and d ϕ over the Kashmir Basin

Shear strength parameters

The shear strength parameters, cohesion intercept (c) and angle of shearing resistance (ϕ) were estimated in the consultancy reports from direct shear tests (DST) conducted on undisturbed in-situ soil samples at natural moisture content and density. The tests were conducted by the consultants at high strain rates such that the drainage condition remains undrained giving the critical values of shear strength parameters. As per the IS Code, to impose undrained conditions, a strain rate higher than 0.2 mm/min for sands and 0.01 mm/min for clayey soils is required. DST was performed under three normal stresses on each sample, and the failure envelope was drawn from which c and ϕ were estimated. The maps developed for c and ϕ also show a specific pattern in the variation in the region (Fig. 8c, d). Cohesion intercept (c) is higher in the central portion of the valley filled with alluvium and also in some regions occupied by values occurring in the central portion occupied by alluvium and Karewa. The peripheral regions, however, show very high values due to the presence of coarse-grained deposits. The value is low in the regions where mountainous soils and coarse deposits are present. Angle of shearing resistance (ϕ) follows an almost opposite trend, with a minimum value in the central portion and a high in the peripheral areas.

Statistical characteristics of geotechnical properties within sedimentary deposits

The sedimentary deposits within the Kashmir Basin are divided into two major groups, viz. Pleistocene Karewas and recent alluvium. Karewas have wide variations in types with coarser sand, gravels, and cobbles found in the higher elevations near their contact with the Panjal traps, whereas finer silts, clays, and sands are concentrated in the comparatively lower reaches closer to the topographic divide. Further, the recent alluvium can also be broadly categorised as fine and coarse depending on the stage of the river when it deposits its load in its flood basin. In view of the fact that Karewas and Alluvium are two major geological units which constitute form the sedimentary deposits in the central basin portion of the Kashmir region over which major cities are established, their characterisation forms a primary input in understanding the geotechnical vulnerability of the region. Therefore, in this study, we provided special attention to the study of the variability of properties within these deposits. Out of the total 600–700 data points, ~ 200 are associated with Karewa deposits, ~ 300 with the alluvial deposits, and the rest with mountainous regions, hills, and foothills. A summary of the range of the geotechnical properties associated with the Karewas and Alluvium is presented in Table 1.

Table 1 Summary of the geotechnical properties of the sedimentary deposits within the Kashmir Basin

Figure 9a–h represents the statistical distribution of the various parameters of the sedimentary deposits in the form of histograms and charts. Figure 9a, b summarises the predominant grain size composition of the deposits (Karewas and Alluvium) with respect to various depths, viz. 3, 6, 10, 15, and 20 m. Around 70% of the investigated soil sites in both deposits are fine-grained (silty and clayey), with less than 30% being coarse-grained (sand and gravel). It is also observed that the percentage of sites with coarse deposits increases at greater depths, suggesting an increase in particle size with depth. The bulk unit weight of the alluvium is centred around 19 kN/m³ with around 80–90% of the sites with γ_b ranging between 17 and 20 kN/m³ (Fig. 9c, d). On the other hand, for Karewas, a relatively higher γ_b of the soil deposits is observed with around 80–90% of sites having γ_b in the range of 19–21 kN/m³. Very high γ_b values have been consistently measured in Karewa deposits in the Pulwama region implying high density and consolidation of the soils. The weighted average of SPT N value with depth (N₃₀) was calculated for all sites such that it represents the gross stiffness of the surficial soil deposit at a site. A sharp distinction is observed in the N₃₀ values in the two categories of sedimentary deposits (Fig. 9e, f). In the alluvial soils, N₃₀ is predominantly centred around 10–12 with 40% of the total sites showing such values. These sites correspond to the fine alluvium, especially in low-lying areas receiving sediments in the later stages of major rivers like Jhelum and Sindh. The second predominant group of sites (~ 12%) show refusal, signifying very high stiffness. These sites mostly correspond to the coarse alluvium deposited in the initial stage of the rivers at higher reaches. In the Karewa deposits, the distribution of N₃₀ is relatively more uniform; however, it gravitates more towards higher values with around 40–50% of the sites showing high SPT N resistance > 40 and even refusal. In general, the sites predominantly show N₃₀ greater than 20, which points to the high stiffness of these deposits when dry. These high values, as well as refusal, are obtained in coarse as well as finer soils within the Karewas, indicating the high density, stiffness, and overall strength of the soils. As mentioned earlier, the presence of elements like calcium and magnesium (Mukhtar 2008) in addition to the consolidation over thousands of years (ageing effect) could be the reason for these unexpectedly high resistance values in the Pleistocene deposits. The histograms showing the statistical distribution of V_S,30 at sites located within the Karewa and Alluvial deposits are presented in Fig. 9g, h, respectively. It is seen that 40–50% of sites in the alluvial deposits show V_S,30 in the range of 150–250 m/s, while on the other hand, > 55% of the sites in Karewa deposits have V_S,30 greater than 300 m/s. This shows that, in general, Karewa deposits are much stiffer than the alluvial deposits, matching well with the conclusions drawn from the variation of N₃₀ values (Fig. 9e, f).

Fig. 9

Histograms showing variability of the type of soils found within a Alluvium and b Karewa deposits at various depths; variability of unit weight (γ) within c Alluvium and d Karewa deposits; variability SPT N value (N₃₀) within e Alluvium and f Karewa deposits; variability of V_S,30 within g Alluvium and h Karewa deposits in the Kashmir Basin

Based on Casagrande’s plasticity chart for the fine-grained portion in the soils (Fig. 10), the alluvial soils behave chiefly as low plasticity silts and clays, and Karewas as low-intermediate plasticity soils. It is worth noting, that the points fall very close to the A-line, suggesting that the behaviour of silts and clays is not much different. Another observation regarding the clay minerals based on nearness to U-line and A-line in the plasticity chart is that the clay mineral is either Illite or Kaolinite, with Montmorillonite at very few sites. This result was also obtained through XRD testing by Zahoor et al. (2021) for soils in the Srinagar region. Illite and Kaolinite because less active minerals show minimal swelling and shrinking effects, thus explaining the low plasticity and compressibility characteristics as derived from the classification. The information on plasticity characteristics is further reflected in Fig. 11a–d which shows the statistical variation of the liquid limit and plasticity index for the deposits. Both Karewa and alluvium show a similar range of liquid limit (30–50%) and plasticity index (10–20%). Very low values (< 5%) correspond to the coarse-grained categories of these deposits. The Compression Index (C_C) is higher in alluvial soils than in Karewa deposits (Table 1), indicating potentially greater consolidation settlements in the former than in the latter. This corresponds with the fact that settlement issues have been reported in the alluvial plains of Jhelum (pers. Comm. Prof. B. A. Mir, NIT Srinagar). Land subsidence and settlements could be a cause of major concern in the alluvial deposits and wetland areas. It must be noted that overconsolidation ratio (OCR) could not be estimated from the reports due to a lack of required data in the reports.

Fig. 10

Casagrande’s plasticity chart for the a Alluvial and b Karewa soils in the Kashmir region

Fig. 11

Histograms representing the variability of Atterberg limits—liquid limit within the a Alluvium and b Karewa deposits and plastic limit within the c Alluvium and d Karewa deposits in the Kashmir region. Variability of the shear strength parameters—cohesion intercept (c) within the e Alluvium and f Karewa deposits and angle of shearing resistance within the g Alluvium and h Karewa deposits in the Kashmir region

The histograms for shear strength parameters associated with sedimentary deposits in Kashmir Basin are presented in Fig. 11e–h. It is evident that the alluvial soils generally show lower values of cohesion intercept ranging between 0.1 and 0.3 kg/cm² for around 50–60% of the sites, and most of the values centred around 0.23 kg/cm². The angle of shearing resistance (ϕ) for such sites ranges between 10 and 15° which is considered as low. Very low cohesion intercept values (almost equal to zero) and higher ϕ (> 30) correspond to the coarse alluvium sites (~ 20%) which comprise cohesionless sands and gravels. The Karewas, in comparison with alluvium, show a higher c–ϕ range (0.2–0.3 kg/cm² and 13–20°, respectively) centred around 0.28 kg/cm² and 18°, respectively. These values indicate a greater shear strength and corresponding bearing capacity of the Pleistocene deposits with respect to alluvial soils. Further, the extremely low values of cohesion intercept (~ 0) and high values of ϕ (> 30°) correspond to the ~ 17% sites with coarse-grained category of the Karewas, especially gravel.

Geotechnical-cum-geological cross sections for Kashmir Basin

The geological cross-section for the complete Kashmir Nappe Zone (Kashmir Basin) showing the major formations and the associated tectonic structures is well established (Wadia 1975). The Kashmir Nappe Zone is filled with Pleistocene deposits over a synclinal basin composed of Palaeozoic, Mesosoic, and Proterozoic sequences. In this study, we attempted to create detailed geological cross sections within the soft sedimentary deposits of the Nappe Zone which are constituted by Pleistocene Karewa deposits and Holocene Alluvial deposits. Seven transverse and five longitudinal profiles were selected as shown in Fig. 12 such that all the major areas with different geology are covered. Geological information and observations from visual investigations of soils in the field were used in conjunction with images from Google Earth, for a better representation of the geological formations at a location along the transect. This information is superimposed with the elevation profiles (above mean sea level), along with particulars of rivers and lakes crossing the transect.

Fig. 12

3D image of Kashmir valley and surrounding mountain ranges, with areas covered with Karewa deposits marked in blue (developed in ArcScene). Red lines represent transverse and longitudinal profiles along which cross sections have been developed in this study

Geotechnical borelogs up to 30 m depth at selected locations have been created to correlate the soil type with the geological formations. The geological cross-sections and the geotechnical borelogs in each formation along the transverse profiles are presented in Fig. 13, and along the longitudinal profiles are illustrated in Fig. 14. Based on the combined geological and geotechnical information, a few points have been observed while constructing the profiles which have in turn assisted in further refining our judgement. These points are supported by information from google earth images as well as geotechnical data and are as follows:

• i. The area around rivers is primarily filled with alluvium, which can be fine grained as in Srinagar and Sopore area of Baramula, or coarse grained at higher elevations. Other water bodies like lakes are also associated with fine soils deposited by the water body.

• ii. The topographic divide separates the elevated Pleistocene Karewas on the southern end from the alluvial deposits in the depressed northern portion.

• iii. The Karewa deposits cover the gradually increasing slope on the southern part of the valley and merge with the hard rock terrain (Palaeosoic and Mesosoic sequences). On the northern end, however, the sedimentary deposits suddenly merge with the hard rock terrain.

• iv. The borelogs indicate finer particle size in the central parts of the valley, both within Alluvial as well as Karewa deposits. As the elevation increases, the soils become more coarse-grained (composed of sands and gravels). The soils in the mountainous and hilly regions are formed from weathered rocks and gravel.

• v. Besides geotechnical factors, geological hazards play an important role in the design and planning of constructions in a region. Landslides, slope instability, earthquakes, and floods should be considered in the design of any structure in the Kashmir Basin (Romshoo et al. 2020).

Fig. 13

a, c, e, g, i, k, m Geological cross sections developed for Kashmir region along the transverse profiles A_A’ to G_G’ and b, d, f, h, j, l, n borelogs up to 30-m depth for sites located within typical geological formations (drawn to a vertically exaggerated scale for clear visualisation). Blue dashed line shows the water table depth at each borehole site

Fig. 14

a, c, e, g, i Geological cross sections developed for Kashmir region along longitudinal transects 1_1’ to 5_5’ and b, d, f, h, j borelogs for sites located within typical geological formations (drawn to a vertically exaggerated scale for clear visualisation). Blue dashed line shows the water table depth at each borehole site

Comparison with neighbouring regions

Peshawar Basin is an oval-shaped intermontane depression within the mountain ranges of the Himalayas, comprising filled with lacustrine and deltaic deposits overlain by floodplain and alluvial fans (Hussain et al. 1998). Showing signs of Late Quaternary deformation due to the tectonics in the Himalayas and the deposition of young alluvial sediments makes it somewhat similar to the Kashmir Basin. Peshawar Basin sediments are mostly unconsolidated deposits of low-medium plasticity (plasticity index < 14%) silts and clays, with poorly graded gravels and sands (Ahmad et al. 2013; Islam et al. 2020). Other geotechnical parameters are reported as c ~ 20–70 kPa, ϕ ~ 11–40°, and SPT N values of ~ 10–20. It must be noted that even though the basins seem similar at first glance, the deposits may show varied behaviours depending on several factors like soil type, topography, environmental conditions, and climate. Besides, Kashmir has a unique geology and geomorphology due to a conspicuous series of events contributing to its development. The most remarkable is the genesis of Karewa highlands—remnants of the ancient Karewa Lake—which is a rare phenomenon that has not been witnessed in any other basin worldwide.

Application to urban planning in the Greater Srinagar metropolitan

The Master Plan-2035 (Town Planning Organisation of Kashmir Region 2017) has laid out the proposal for the urbanisation of the Srinagar Metropolitan Region, recommending the Karewa highlands as the zones of future developments. As a form of application of the results attained in this study, the bearing capacity and liquefaction susceptibility of the soils in the Greater Srinagar metropolitan have been assessed, in an attempt to contribute to the ongoing urbanisation process.

Bearing capacity of shallow strip foundations

Foundations are designed based on serviceability and strength criteria prescribed by various codal provisions (e.g. IS 6403: 1981). The gross pressure that a footing can handle without failing in shear is the bearing capacity of the soil. The soil properties along with foundation type and geometry are essential inputs for the evaluation of the foundation bearing capacity. For estimating the bearing capacity of soils in the study area, analytical equations—Meyerhof (1951), Vesic (1973), and BIS (1981b)—were used at each site. The average of the values obtained in these methods was taken as the final value of the ultimate bearing capacity (q_u) of the soils. The primary soil properties (c, ϕ, γ) required for this purpose were retrieved from the geotechnical database collected in this study. The bearing capacity was computed for a shallow strip foundation of an assumed width of 2 m and embedment depth of 3 m. The water table depth from the borelogs verified with the annual average water level was utilised in the calculations. Submerged unit weight (γ_sub) was calculated as ${\gamma }_{\text{sat}}-{\gamma }_{w}$ where γ_sat is the saturated unit weight of soil under the water table and γ_w is the unit weight of water. Since the consultancy reports mention unit weight under one heading (γ_b), so γ_sat is equal to the reported γ_b when soil is under the water table. Figure 15a presents the variation of q_u for the soils in the Greater Srinagar metropolitan. The figure illustrates that the bearing capacity of soils around the Jhelum River is much lower than the peripheral soils consisting of Karewa and mountainous deposits. The trend corroborates well with the variation of properties like SPT N, V_S,30, and water table depth. Ministry of Business, Innovation and Employment (2017) recommends that an ultimate bearing capacity of 300 kPa or more may be considered representative of very good ground conditions; within the range of 200–300 kPa may be considered acceptable; whereas values less than 200 kPa should not be allowed where liquefaction hazard is expected. Following this broad classification, the Greater Srinagar metropolitan has been divided into zones in Fig. 15a. The figure indicates low values of q_u in certain areas within the Jhelum floodplains as compared to the other geological units, revealing yet again the critical nature of these deposits. q_u is less than 300 kPa at the majority of the sites within the alluvial floodplains. As such, the alluvial sediments have low strength which is made worse due to the presence of a shallow water table. On the other hand, Karewa deposits show much higher values of bearing capacity.

Fig. 15

Maps representing the spatial distribution of the a ultimate bearing capacity q_u and b liquefaction susceptibility (grade I) based on values of Ls in the Greater Srinagar region

Liquefaction susceptibility

Qualitatively, the liquefaction susceptibility of an area can be assessed by studying its geological, topographical, and geomorphological characteristics. In addition to the susceptibility of surficial deposits, the seismic environment including the proximity of seismic sources and the probability of exceedance ground motions expected at a site, plays a critical role. This has been established in several earlier studies (Satyam and Rao 2014; Ansari et al. 2022). The Grade-I liquefaction hazard map developed through this procedure is beneficial as an initial guide for the identification of critical zones within an area where a high liquefaction hazard is anticipated and therefore, a further detailed geotechnical investigation is required for liquefaction potential assessment. Six thematic layers were considered for the liquefaction susceptibility of the region, namely, amplification factor, geomorphology, peak ground acceleration (PGA) zones, SPT N, groundwater table depth, and lithology (Zahoor 2023). These factors include the characteristics of the soil deposits and the seismic environment of the region. Lithology and N are directly related to the geotechnical properties of the soils, illustrating the vulnerability of the soils to liquefaction. Geomorphology includes the type of deposit, environment of deposition, as well as age of the deposit. The presence of a groundwater table within 10–13 m depth is important for liquefaction to occur. Deep or absent water table throughout the seasonal variations in a region would signify safety against liquefaction.

Lithology was used to estimate the susceptibility to liquefaction based on Seed et al. (2003) criteria. The corrected SPT N value (N_corr) was obtained by using corrections for overburden pressure and fines content by Boulanger and Idriss (2014). The values were corrected to 1-atmosphere overburden pressure. For incorporating the variation of the ground shaking parameter, the PGA zones developed for Kashmir Basin (Zahoor et al. 2023b) are considered. The five seismic zones for the valley are, namely, ZA-ZE (highest to lowest seismicity), such that Greater Srinagar falls under zones ZB-ZE. Further, the amplification factor (AF) at a site includes information about the soil deposit as well as the seismicity of the region. For this study, the amplification factors determined from 1D ground response analysis by Zahoor (2023) have been utilised. Liquefaction susceptibility of the Greater Srinagar metropolitan has been assessed by integrating the relevant thematic maps using the Analytical Hierarchy Process (Saaty 1990). In this respect, a comparison matrix was constructed and is presented in Table 2. A scale of 1–3 has been used to indicate the relative importance of the various parameters considered, with 1 representing equal importance of both units and 3 representing the very large importance of one unit over another. The comparison matrix was further utilised to determine the weightage of each unit through the calculation of the principle Eigen vector of the matrix. The rating of each unit is normalised between 0 and 1, to compute the influence factor for each unit using the following equation:

$${x}_{i}=\frac{{R}_{j}-{R}_{\text{min}}}{{R}_{\text{max}}-{R}_{\text{min}}}$$

(1)

where R_min and R_max are the minimum and maximum ratings for each unit, respectively, and R_j is the rating for the jth feature in the unit.

Table 2 Criteria comparison matrix developed through AHP for liquefaction susceptibility assessment of Greater Srinagar metropolitan

The weightages as well as the influence factors of each unit and sub-classes are presented in Table 3. The susceptibility of liquefaction is estimated as the summation of the products of the influence factors of the sub-features and the respective weightages of the units as follows:

$${L}_{S}={W}_{1}{I}_{1}+{W}_{2}{I}_{2}+\dots {W}_{N}{I}_{N}$$

(2)

where W₁, W₂, … W_N are the weightages of the units whereas I₁, I₂, … I_N are the influence factors for the sub-features.

Table 3 Summary of weightage, ranking, and influence factors for the units and subclasses considered in the AHP for liquefaction susceptibility assessment of the Greater Srinagar metropolitan

Liquefaction susceptibility (L_S) is used as an index to classify the region into zones where liquefaction is likely, possible, or not likely (Puri and Jain 2014; Pudi et al. 2019). The value of L_S has been used to categorise the Greater Srinagar metropolitan into three susceptibility zones, viz. high (L_S ≥ 0.8), moderate (0.5 < L_S < 0.8), and low (L_S ≤ 0.8). L_S has been calculated for over 300 sites in the Greater Srinagar metropolitan and consequently, a Grade-I liquefaction susceptibility map has been prepared (Fig. 15b). Based on the values of L_S, Greater Srinagar has been categorised into three zones of liquefaction susceptibility (low, moderate, and high). The results indicate high liquefaction susceptibility in the Jhelum floodplains and medium susceptibility in the Karewa highlands/terraces. Low/negligible susceptibility has been attained in the mountainous soils in the hills.

General recommendations

The interpretation of the geotechnical and geological information presented in this study, suggests that the alluvium plains face critical issues like shallow water table, low penetration resistance, larger settlements, low bearing capacity, and high liquefaction susceptibility. Karewa highlands show deep water table, low plasticity, high penetration resistance, good bearing capacity, and medium–low liquefaction susceptibility. In this regard, it is recommended that within the Greater Srinagar metropolitan, the Karewa highlands are the most suitable for future expansion efforts in the city, whereas Jhelum floodplains and other wetlands are the least suitable. These results are in line with the proposals of the Master Plan-2035 (Town Planning Organisation of Kashmir Region 2017) which has also delineated the Karewa highlands within the ‘cone’ of urbanisation after rigorous studies on socio-economic, ecological, and land use aspects of Srinagar.

The Soura-Buchpora, Pampore, HMT-Zainakote, and Budgam Karewas must be viewed as the zones of future urbanisation, both in terms of the availability of land as well as the geotechnical suitability of the soils for construction. However, the presence of industrial townships in the HMT-Zainakote Karewa and the Khrew-Khunmoh area of Pampore will also limit the admissible extent of expansion (Town Planning Organisation of Kashmir Region 2017). The limestone quarries in Khrew and the brick kilns in Budgam may even affect the long-term environmental stability of the region, which will, in turn, reduce the expansion of the city into such areas. It is recommended that the vertical expansion of the city through multi-storeyed buildings if required be carried out on the stiff deposits of Karewa. The recently constructed multi-storeyed buildings in the wetland areas and Jhelum floodplains may not be sustainable in the long term due to hazards like floods, liquefaction, as well as delicate ecology, as pointed out in the Master Plan. Further, ground settlements can pose a serious risk in the alluvial plains and wetlands, causing potential instability in the structures. In case any construction is taken up in these vulnerable areas, extensive ground improvement measures, appropriate foundation choice, and proper design must be carried out to counter the ground subsidence hazard, high liquefaction susceptibility, and low bearing capacity of the soils.

Future scope

The results of this study will hopefully serve as a technical contribution to the ongoing plans of urbanisation for the Srinagar Metropolitan City. The scope of this study is to provide estimates of the geotechnical parameters at a regional scale to frame a fundamental understanding of the soils in the Kashmir Basin. The maps presented herein do not describe the seismic amplification hazard in the sedimentary deposits; however, these can be used in future as the base layer for seismic microzoning in the region. The maps and results must, however, be used with caution since the properties are mapped at a regional scale and, therefore, do not furnish site-specific information, limiting its application as a preliminary guide for geotechnical assessment. Since this is the first attempt at characterising the soils in the Kashmir Basin at such a scale, the study has its own potencies. There are limitations as well, mostly stemming from the paucity of certain test data within the consultancy reports which therefore could not be included in the results. The future scope of the study thus includes further testing like Hydrometer tests to determine silt and clay content, and detailed consolidation tests to estimate overconsolidation ratio (OCR) in fine-grained soils. Likewise, the interpretation of tests like Static Cone Penetration Tests (SCPT) in coarse-grained soils and the estimation of settlement parameters may also be followed through in detail. Moreover, it is important to mention that geological hazards like slope stability issues and landslide hazards must also be given serious consideration in designing foundations and superstructures.

Conclusion

This study aims to present a spatial distribution of the geotechnical characteristics of the predominant soils in the region and depict information about the geological aspects of the Kashmir Basin. Basic geotechnical properties of the sedimentary deposits in the region have been assessed with the help of a database collected from borelogs at about 700 locations in the Kashmir region from NIT Srinagar as well as geo-consultancies in the region. 2D geological-cum-geotechnical cross-sections have also been developed using information from geology, geotechnical datasets, as well as Google Earth images. It was found that the predominant soils in the northern part of the valley depression are alluvial deposits which are unconsolidated, soft, saturated, and potentially liquefiable. The southern flank is mostly laced by Karewa terraces, which are stiff and dry, with deep water table, forming the topographic rise within the region. The hills and mountains surrounding the basin are composed of mostly colluvial and glacial soils overlying shallow bedrock. SPT N values show that the Karewas are stiff (N ~ 10–50) with a deep water table, whereas the alluvial deposits are soft (N < 20) with a shallow water table. Grain size distribution shows that the central portion of the valley is composed of fine-grained soils with coarser material predominant at the periphery. The sedimentary deposits, in general, show low plasticity (plasticity index < 17%) as well as the presence of stable clay minerals like Illite and Kaolinite, ruling out the issue of swelling and shrinkage for building foundations. The presence of saturated, loose sands in the vicinity of rivers points out the high risk of liquefaction hazards. The compression index (C_C) is lower for Karewas (0.08–0.27) as compared to alluvium (0.16–0.36) indicating higher settlement hazard in the latter. Mountainous regions show higher shear strength as compared to the sedimentary deposits of Karewa and alluvium.

Bearing capacity and liquefaction susceptibility assessment for the soils in the Greater Srinagar metropolitan has been conducted to contribute to the ongoing urbanisation of Srinagar City. The results reveal that the floodplains of Jhelum are critical in terms of both low bearing capacity (< 300 kPa) as well as high liquefaction susceptibility (L_S > 0.8). Appropriate geotechnical foundation design is required at such sites to counter these issues. The Karewa highlands, on the other hand, seem to have much higher capacity (> 300 kPa) as well as medium liquefaction susceptibility (L_S > 0.5–0.8). Owing to the better geotechnical properties of the Karewa deposits as inferred from this study, it is recommended that these highlands be considered as areas for future expansion of the city. Based on the good bearing capacity and low liquefaction susceptibility of Karewa deposits, vertical expansion through the construction of multi-storeyed buildings may be proposed in these highlands as opposed to the wetlands and floodplains. For the vulnerable zones, proper foundation design and/or ground improvement techniques must be carried out to counter the effects of liquefaction and low bearing capacity.

The present study and the results thereof are expected to form an integrated resource of geotechnical and geological information about the Kashmir Basin. The type of soil and the engineering properties are essential inputs for the design of foundations of structures. The aim is to predict the distribution of geotechnical problem areas and thus help engineers in planning civil engineering works accordingly. The engineering characteristics, along with the geological information, will be helpful for deciding the suitability of the areas for various types of constructions. For site-specific design procedures, these maps would typically require additional information from detailed site-specific geotechnical and geological studies. This critical knowledge of the Kashmir Basin forms the cornerstone for the seismic hazard and geotechnical vulnerability studies in the region. This study is an engineering contribution to the ongoing development in the region, which is missing in the Master Plan-2035 report. The integrated geotechnical and geological outputs of this study offer a technical supplement to the Master Plan and, hence, to the town planning initiatives. The maps produced herein may be used as a direct input layer in the Master Plan for deciding the zones of expansion of the city in order to consider the vital geotechnical aspects of the soils. Moreover, the study forms a solid ground for future rigorous studies in Kashmir to provide specific guidelines regarding the types of foundations and ground improvement methods required in different zones.