A Research On The Consolidation Settlement And Stability Of Soft Clay Ground With Structure Characteristic

Since the soil structure characteristic is an intrinsic determinative factor of soft clay engineering property,it is necessary that experiment and theory research on the soft clay structure characteristic be carried on in order to explain the consolidation settlement property of the soft clay ground. In this dissertation,on the basis of the existing work,the consolidation settlement and the stability of the structural soft clay ground have been studied with the methods,such as the structure characteristic experiment of soft clay,modeling and theory analysis.The systematical experimental study on the structure characteristic of soft clay from Wenzhou has been carried out. Based on Schmermann and Nagaraj's experimental conclusions and a large number of structure characteristic experiments of soft clay from Wenzhou,an updated correction method of compression curve of disturbed soil is presented. The corrected compression curve is composed of four sections:horizontal section,elastic compression section,structure dilapidation compression section and normal compression section. The compression curves of soft clay of different disturbance degree finally intersect at 0.42eo.The subsection models of the CV-P curve and the k-p curve are presented on the basis of the experiments. The basic consolidation settlement theories of structural soft clay ground are set up herein. At first,an analytical solution to one dimension consolidation of half-infinite homogeneous structural soft clay ground is derived,then analytical solution to one dimension consolidation of finite thickness homogeneous structural soft clay ground are given. In the meantime numerical solution to one dimension consolidation of layered structural soft clay ground is derived. Furthermore,the calculation method of the consolidation degree of sand drains ground is given under the condition of instant loading,where soil structure characteristic is taken into the formula account. In addition,an assessment method of disturbance degree of soft clay ground is put forward,and the problem of extra settlement resulted from disturbance is investigated. One dimension compression model of disturbed soil is presented,and the formula of the settlement and extra settlement of disturbed soft clay ground is derived. The difference between disturbed soft clay and field soft clay is compared,and the example suggests that the disturbance degree resulted from the construction of prefabricated band drains is about 30%. The disturbance slower the consolidation of the soft clay ground,and the extra settlement resulted from disturbance is also notable. To verify the theory developed herein,the analytical solutions are compared with the field measured ones,which shows that they are in a good agreement.The strength line of consolidation undrained shear of field soft clay is polygonal.on the basis of the character,and the calculation formula of stability and strength increase of structural soft clay ground can be obtained. The example shows that the structural soft clay ground maybe destroys during the preceding loading. Finally,strength increase and its utmost are discussed,associated with the analysis of the example,and some useful conclusions are obtained.