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SUMMARYThis study attempts to address some problems associated with excavation analysis by means of the stress-#ow coupled method. This is done through the investigation of two examples, both of which are excavation analyses modelling a sequential excavation process. The "rst example is a three-dimensional elastic analysis of a tunnel constructed in soft rock layer. The second example is an axi-symmetric elasto-plastic analysis of a shaft constructed in slightly overconsolidated clay layer. In order to clarify the e!ect of sequential excavation process on the analysis results, a conventional two-dimensional analysis on each example is also carried out. Through this study, we will demonstrate that it is essential to consider in detail the incremental advance of a tunnel face when one investigates the change of pore water pressure and stresses surrounding a tunnel face during excavation. Additionally, on the basis of the analytical results obtained, a proposal is presented for evaluating the stability of rock mass surrounding a tunnel during construction.

An evaluation method that can express the local leakage of leachate from joint sections in steel pipe sheet pile (SPSP) cutoff walls is discussed in this study. In particular, the evaluation of environmental feasibility (containment of leachates containing toxic substances) considering a three-dimensional arrangement and hydraulic conductivity distribution of the joint sections in the SPSP cutoff wall is compared with an evaluation that uses the equivalent hydraulic conductivity. This equivalent hydraulic conductivity assumes that the joint section and the steel pipe are integrated; therefore, the hydraulic conductivity is substituted with a uniform permeable layer. However, in an evaluation that employs the equivalent hydraulic conductivity, it is diffi cult to consider the local leakage of leachate containing toxic substances from the joint sections in the SPSP cutoff wall. It was established that evaluations of the environmental feasibility of SPSP cutoff walls with joint sections must take into account the local leakage of leachates containing toxic substances from the joint sections. Also, it was clarifi ed that technologies that lower the hydraulic conductivities of joint sections in SPSP cutoff walls and also facilitate the use of sparser joint arrangements contribute signifi cantly to increasing the environmental feasibility of SPSP cutoff walls at landfi ll sites.Key words Coastal landfi ll site · Environmental feasibility · Local leakage of leachate · Steel pipe sheet pile · Vertical cutoff barrier J Mater Cycles Waste Manag (2009) 11:55-64

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