Earth, Atmosphere & Environment Sciences
Title : | Stochastic Analysis for Geotechnical Problems on Active State Soil Failure Using Lower Bound Theorem |
Area of research : | Earth, Atmosphere & Environment Sciences |
Focus area : | Geotechnical Engineering |
Principal Investigator : | Dr. Paramita Bhattacharya, Indian Institute Of Technology (IIT) Kharagpur, West Bengal |
Timeline Start Year : | 2024 |
Timeline End Year : | 2027 |
Contact info : | paramita@civil.iitkgp.ac.in |
Details
Executive Summary : | Soil is a heterogeneous and anisotropic material. The uncertainty in soil properties is found due to inherent soil variability, measurement error during the determination of soil properties, and transformation uncertainty. The inherent anisotropy and inherent randomness in the shear strength of soils are introduced during the deposition and sedimentation of the soil. The influence of the inherent soil variability in Geotechnical Engineering problems on active state failure of soils will be studied in the proposed research work. For this, a detailed understanding of the different distribution functions used for generating the random field is required. Although lognormal distribution is popular in geotechnical engineering dealing with the random field the shear strength parameters, say soil cohesion and soil friction angle, are bounded by possible maximum and minimum values depending upon soil types. Also, for granular soil, the dilatancy angle is another important parameter for consideration. The research work will investigate the role of different distribution functions like lognormal distribution with upper and lower limits, bound distribution, Beta distribution, and Gamma distribution of soil friction angle and dilatancy angle for modeling the random field in geotechnical engineering problems like stability problems of underground tunneling/openings, maximum earth pressure of soil at the active state of failure. Following Phoon and Kulhawy (1999) the mean value and standard deviation of soil friction angle and dilatancy angle will be set to calculate the shape coefficients α and β for Beta distribution, shape, and scale parameters α and β for Gamma distribution and mean and standard deviation of ln(tanφ) in lognormal distribution. Then cross-correlation will be used between these two random variables. Different laboratory tests illustrated that the dilation of granular soil depends upon its relative density and thus dilatancy angle is correlated to the soil friction angle. The limit load of geotechnical engineering problems can be determined either by displacement-based finite element method or numerical analysis. Numerical limit analysis using the lower bound limit theorem shall be used for this study, as it takes less computation time and is easy to achieve the converged solution without tracing the complete load-displacement curve. In lower bound limit analysis, a statically admissible stress field is constructed by satisfying the element equilibrium conditions, stress boundary conditions, and yield criterion. The spatially varying shear strength parameters will be used in the Mohr-Coulomb yield criterion. The analysis will be carried out for 1000 Monte-Carlo simulations and thereafter mean and standard deviation of the output parameters (which are peripheral support pressure for underground openings and active earth-pressure coefficient for backfill soils of retaining walls) will be determined. The goodness of fit test will be carried out. |
Total Budget (INR): | 6,60,000 |
Organizations involved