Sustainable Implementation of Standard Geotechnical Practices to Optimize the Foundation Design of a Residential Building: A Case Study

Every site on earth is unique in its own way. Two work sites usually do not have the same sub-soil profile with identical properties. From an engineering point of view, conducting a geotechnical investigation at any site where a structure is being constructed is essential. Geotechnical investigation methods can be effectively employed based on the nature of construction, anticipated super-structural loads, and scope of the project. Precise and standard procedures shall be adopted to arrive at the optimal type and size of the foundation. In residential projects, where parent ground consists of loose or non-uniform soil stratifications, placing the shallow foundation on top of the engineered fill is routine. This paper presents a case study of a site consisting of 3 m of compacted silty sand-engineered fill. Inconsistent standard penetration resistance (N) values were reported at the founding level across different borehole locations on the site. Due to inconsistent N values, different safe-bearing capacities were reported. A raft foundation was initially planned and the philosophy of a shallow sub-structure system could not be adopted with uneven bearing pressures across the site. A root cause analysis by conducting in situ density tests revealed non-uniform or improper compaction methods adopted at the site leading to improper densities of topsoil across the site. Proper compaction control and engineered fill construction were adopted at the site to arrive at optimal foundation dimensions. Further, the measurement of the energy transfer ratio, proper tools, and quality procedures adopted in the geotechnical investigation program have added value toward sustainability in construction practice.