Compressibility of Composite Ground Treated by Deep Mixing Method

• Main Authors: Jan, Guo-Ming, 詹國明
• Other Authors: Chang Huei-Wen
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/43144310582149175576

碩士 === 國立中央大學 === 土木工程學系 === 86 === Deep Mixing Method is a chemical soil improvement technique using cement slurry or quick lime as a hardening agent, which can apparently increase the shear strength and bearing capacity of soft ground, and reduce its consolidation settlement. Large columns of treated-soil are formed by the operation of DM machines. Treated and untreated soils will coexist both in the ground called "Composite Ground". Within the composite ground, the mechanical behavior of treated and untreated parts will be different. It is important to realize the interaction and the difference between the two materials. To perform shear tests and consolidation tests, this research use Taipei silt as an improved object to make the cylindrical treated-soil and composite specimen which has a cement treated soil column in the center with untreated soil around. In consolidation tests, the behavior of consolidation and the effect of reduction in settlement due to mixing with cement will be investigated. In the tests, the stress acting on treated-soil column and the lateral pressure will be measured in order to realize the bearing mechanism of composite ground. In addition, this research use the simple calculation to estimate the final settlement of composite ground. Although the procedure is based on simplified assumption, the result shows relatively good agreement. Furthermore, in order to investigate the bearing capacity of the soft ground improved by deep mixing method, this research made a real scale model in the large scale test pit. A composite ground contained a treated column with 3 feet diameter was prepared. After curing for 7 days, a rigid bearing plate was placed on top of this model to realize the increase of the bearing capacity of this treated ground. In addition, to realize the bearing mechanism of the treated ground, load cells were put under the bearing plate to measure the stress of the treated column and untreated soil.