Time-Dependent Effects On Vertical Shafts Used In Micro-Tunneling applications In Queenston Shale - Year two
Micro-tunneling technique is a feasible means to construct pipelines and tunnels in different types of ground including Queenston shale. However, this shale exhibits time-dependent deformation behavior, generally known as the rock swelling, which produces additional stresses on underground structures. These stresses may exceed the allowable tensile or compressive strength of concrete of the pipeline or the tunnel liner, which in-turn may result in cracks in these structures. It is suggested here to investigate induced stresses in vertical shafts constructed in swelling rock and their impact on the stability of these shafts. Employing PLAXIS computer program, a numerical analysis approach is proposed to calculate induced stresses on vertical shafts used in micro-tunneling applications. The results of the numerical analyses will aid in adopting suitable construction procedure that minimize the induced stresses in vertical shafts. Recommendations in this regard will be provided to micro-tunneling contractors to mitigate the influence of induced stresses.