Subsurface geotechnical information (e.g., engineering and geophysical properties of soil) is essential for designing and constructing geotechnical projects (e.g., earth dams, foundations, excavation, embankments, and seismic hazards analysis). Geotechnical properties (e.g., N value from the standard penetration test (SPT), bearing capacity, shear modulus, permeability, stiffness, and strength) are affected by the size, shape, microscopic structure, and arrangement of soil particles (Sharma & Rahman, 2016). These properties can be determined through drilling boreholes and geophysical surveys; however, this data covered a limited surface and subsurface area. Moreover, getting the data of a large area using drilling and geophysical methods involves a high cost. Most of the time, geotechnical engineers rely on the limited available data and try to interpolate between boreholes, which generates a need to explore different interpolation techniques for knowing the spatial distribution of geotechnical properties.
Soil classification, SPT N-value, and shear wave velocity are the most significant geotechnical parameters in designing a foundation, computing the allowable bearing capacity (ABC) of the shallow foundation and the axial capacity for both types of foundations (e.g., driven and bored). The properties of cohesive and non-cohesive soils (e.g., consistency and compressive strength of cohesive soils, compactness, relative density, angle of friction for cohesionless soils, shear wave velocity) and allowable bearing capacity of the shallow foundation are estimated from SPT N-value. Multiple empirical relationships have been established between SPT N-value and shear wave velocity because shear wave velocity is the most critical parameter for studying site response against earthquakes. In geotechnical earthquake engineering, the shear modulus is an important parameter estimated from shear wave velocity and used to determine the dynamic response of the soil. Bandyopadhyay, Sengupta, and Reddy (2021) have conducted site response analysis based on the soil classification, soil resistance parameters, and shear wave velocity for different soils and found that soil type significantly impacts this analysis.
The geographical Information System (GIS) is a valuable tool for capturing, presenting, and analyzing geographically referenced data (Singh, Noor, Chitra, & Gupta, 2018). Geographic Information System provides valuable tools for inputting data into the database, retrieving specific data items for further processing, and software components that can evaluate or manipulate the recovered data to produce desired information in a particular form (Mhaske & Choudhury, 2011). Geotechnical evaluation of an area requires an optimum number of data points to develop a comprehensive surface/subsurface model. GIS can be used for analyzing/mapping a bulk volume of data for geotechnical investigations. In geotechnical practice, GIS is used in four ways: data integration, data visualization and analysis, planning and summarizing site activities, and data presentation (Singh et al., 2018). Due to the fast-growing of engineering technologies, the modern techniques of geography are combined with engineering to form new strategies for data integration. The corrected SPT N-values, soil types, groundwater depth, shear wave velocity, and allowable bearing capacity for shallow foundations are mapped using the Geographic information system through spatial data treatment and management. Kriging and IDW (Inverse distance weight) are the user-friendly techniques available in GIS for mapping the data. However, an evaluation of these geostatistical techniques is necessary to decide the suitability of a specific technique for a certain area.
Lahore has an estimated population of 11.738 million (Desa, 2018), which demands the launch of more infrastructure development projects. Considering the demand for infrastructure developments, conducting detailed subsurface geotechnical investigations is essential. Previously published studies (Khan, Rashid, Israr, & Zhang, 2022; Shafique, Khan, Mustafa, & Arif, 2012) on Lahore focussed on a few parameters and missed several parts of the city, which constrain the applicability of those studies throughout the city. This study collected data from boreholes drilled at different locations in Lahore city, and maps of geotechnical properties were constructed using GIS.
Study Area
Lahore is Pakistan's second largest metropolitan city and the capital city of the province of Punjab. It is also the 18th largest city in the world. It is located at 31°32′ 59″ N and 74°20′ 37″ E with a covered area of 1,772 km2. Lahore city has a very high population growth rate, and its urban growth has increased by 32% in the last 20 years.
Lahore is at an average elevation of 210 meters above mean sea level. Lahore rests on the Bari Doab, which is an alluvial plain. Bari Doab belongs to the Indo-Gangetic alluvial plain, which the Indus River and its tributaries create. This doab consists of Quaternary alluvium, which overlies Metamorphic and igneous rocks of the Precambrian age and semi-consolidated Tertiary rocks (Kadwai & Siraj, 1964). The alluvial compound of Pleistocene and current age denotes the modern sedimentation in an environment that has its commencement in the Mid-Tertiary periods. This alluvial compound mainly consists of silt, clay, and fine to medium sand (Malik, 2015).