Soil Bearing Capacity Estimation using Plate Load Test for Station 5 of MRT Line -6 at Dhaka: A Case Study

Plate load test (PLT) is a popular and established conventional method for estimating in situ pressure settlement response of soil. PLT provides an accurate estimation of the ultimate bearing capacity of soil which can be useful to design an appropriate shallow foundation for buildings and infrastructures. This study estimated the ultimate bearing capacity of the site soil of station 5 (S5) of MRT line 6 located in Mirpur, Dhaka using four PLTs. An advanced data acquisition system is employed at the site using both a dial gauge system and three automated Linear variable differential transformers (LVDT) in a 20-channel data logger. Subsequently, soil samples were collected from each point to determine their characterization and geotechnical properties. The load settlement responses of all four station points indicate that the site soil is partially cohesive to cohesive. The evidence is also supported by the soil parameters obtained from laboratory tests. Using the test results, the ultimate bearing capacity of soil was determined from different methods namely, double tangent, De Beer, and Terzaghi equation. A comparison of these three methods suggests that the obtained bearing capacity values are very close to the actual test results. A finite element (FE) based numerical investigation was also performed using PLAXIS 3D to simulate actual PLT at the field conditions. The FE result in terms of pressure settlement responses also showed a good agreement with the experimental outcome. Parametric studies were also conducted considering the different depths of the water table, plate diameters, and mesh sizes to see their influence on plate settlement under static loading conditions. Parametric analysis claimed that the water table above the plate level reduces bearing capacity and increases the plate settlement; whereas, settlement is found to decrease as the plate size increases.