Experimental and Numerical Investigation of The Effect of Pre Existing Nearby Conduit or Utility Tunnel on The Load Carrying Capacity of Deep and Shallow Foundation

Abstract

The present study demonstrates the load carrying capacity of shallow and deep foundation, placed in the vicinity of pre-existing buried conduit or utility tunnel in a cohesionless soil. Model experimental studies were first performed to obtain the load-settlement response of shallow foundation and single pile footing, respectively, placed near the existing buried flexible pipe or utility tunnel system. Experimental studies were conducted in a steel box of size 70cm × 60cm × 60cm filled with sand, up to 60cm at two different relative density values (medium with RD = 50% and dense with RD = 80%) without and with buried pipe. In the model study, flexible buried pipe modelled using PVC pipe, size and diameter of which was taken based on dimensional analysis, by considering a real life situation. Model Test results were verified, numerically, using commercially available finite element tool PLAXIS 2D software. After due verification of numerical modelling procedure of stated problem and its load-settlement response, a detailed parametric study was conducted, numerically, by varying the range of input parameters, such as unit weight of sand, angle of internal friction, diameter of buried conduit and the Elastic modulus of the soil. The objective was to assess the expected % reduction in the bearing capacity of the shallow and pile footing due to the presence of buried flexible pipe. It is noted that % reduction in the bearing capacity of a shallow and pile foundation in the vicinity of the existing buried pipe not only depends on geotechnical parameters, but also on the location and diameter of the buried conduit as well as relative stiffness of soil and material of the pipe. It s a complex soil-structure interaction problem. newlineBased on the results of the load settlement curves obtained from the experimental and numerical analysis, analytical solution has been proposed to estimate the reduction in the frictional capacity of a single pile to be installed in cohesionless soil. Design charts has been prepared to directly