Composite Foundation After Grouting, Soil Fracture Mechanism And Model

The post based-grouting in composite foundation is a new technique of ground treatment. At present, few application and study are going on in China. Firstly, based on analyzing the characters of geological body's changing, this paper applies the geological fracture mechanics theory to quantitatively analyze the soil working mechanism of composite foundation after being reinforced by the post based-grouting. Then, the paper applies Vesic soil spherical hole expansion theory to study deeply the soil stress-strain relation during post based-grouting. Lastly, the author compares the collected practice data of the post based-grouting project in one compound building of Nanjing with the result of this paper, and present some new opinions.Firstly, In view of geological fracture mechanics theory, the author analogizes the features of soil deformation and quantitatively analyzes the diffusing characters of cement grout and its controlling conditions, and make a thorough analysis of the soil working mechanism in the pile bottom from the sides of the Q-S curves , the distribution characters of axial load in pile body, the contribution made by the percentage of cements injected into soils and etc.Secondly, In view of Vesic soil spherical hole expansion theory, the author analyzes the relation between the soil deformation in pile bottom and cement liquid under the grouting compress, and deduces the formation of grouting compress and the diffusing radius of cement fluid. When given the grouting compress, the diffusing radius of cement fluid can be calculated.Thirdly, According to the above results, the author offer the method of the optimization grouting design and the calculation of the composite foundation's bearing capacity after the post based-grouting. At the same time, the author makes initial quantitative study on the reinforcement effect of the post based-grouting, and introduces the programs of calculating the bearing capacity developed by Visual Basic 6.0.In the end, the author compares all above results with the realistic engineering data and makes important conclusions and suggestions.