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In foundation engineering, ground improvement is one of the main topics that have been extensively researched in the last few decades. Significant progress has been made on this topic as more advanced technology and machinery has become available. Many techniques, such as deep vibro techniques, vertical drains, jet grouting, and soil mixing, have been developed for various ground improvement applications in different types of weak soils. In particular, two deep vibro techniques, vibrocompaction for treating granular soil and vibro-replacement for treating cohesive soil, have been devised from the original vibro technique that uses a depth vibrator to treat weak soils. With significant evolution in the equipment and technology for deep vibro techniques in the last few decades, the extent of treatment has become deeper and more effective in providing inexpensive and faster alternatives to traditional foundation methods for supporting structures. Even complex ground situations including highly variable mixed sandy clayey ground conditions can be improved using a hybrid vibrocompaction and vibro-replacement approach. This chapter provides an overview and the basic principles of deep vibro techniques. Three case studies in Asia are used as illustrative examples on the successful applications of deep vibro techniques in a variety of ground conditions. In each case study, the subsurface profile and properties are first described. This is followed by discussions on the applications of the relevant vibro technique used for the project. The verifications on the improved ground subject to anticipated loading are presented in detail. For the case study in clayey ground, the results of finite element back-analysis are presented to demonstrate that for typical ground improvement projects, the actual stiffness of stone columns can be much higher than the design stiffness value. |
