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Deep soil mixing (DSM) columns as a retaining structure for deep excavations in soft soil areas has been widely used because, in addition to its low cost, it has fewer environmental hazards and no need of dewatering. However, due to its low tensile strength, this system usually requires a very thick wall cross section and is generally impractical for use as a retaining structure for very deep excavations. In an attempt to extend the use of DSM columns for deeper excavations, this paper introduces a so-called compound DSM retaining wall system that combines DSM columns with reinforced concrete bored piles. As shown in the paper, both the compressive strength of soil-cement mixtures and the bending moment capacity of concrete piles are developed to their full advantage in this hybrid soil-retaining system. The paper also presents the detail design methodology for the proposed compound DSM wall as a retaining structure for deep excavation. Finally, the benefits of this hybrid retaining system are further demonstrated through a case study completed in Shanghai, China. [ABSTRACT FROM AUTHOR]

Purpose - Taking into account the long-term influences of the non-linear behavior of the material as well as the large deformation and contact conditions, the limiting factors of the computer simulation are the computer runtime and the memory requirement during solution of seismic response analysis for immersed tunnel. This research aims to overcome these problems. Design/methodology/approach - This research deals with parallel explicit finite element simulation with domain decomposition for seismic response analysis of immersed tunnel, which is the non-linear and time-dependent behavior of complex structures in engineering. A domain decomposition method based on parallel contact algorithm and dynamic-explicit time integration procedure are used, and the latter is used for the solution of the semi-discrete equations of motion, which is very suited for parallel processing. Using the high performance computer SGI Onyx3800, the seismic response analysis of the immersed tunnel in Shanghai is processed with more than 1.2 million nodes and more than 1 million elements in final finite element model. Findings - The results show numerical scalability of this algorithm and reveal the dangerous joints in this immersed tunnel under Tangshan seismic acceleration, and it could also provide references for the antiseismic design of the immersed tunnel. Originality/value - With the increasing demands in the scale, accuracy and speed of numerical simulation in geotechnical engineering, parallel computing has its great application in this area. This paper fulfils an identified method need, and it is believed more and more research work will be devoted to this research field in the near future. [ABSTRACT FROM AUTHOR]