Test Study And Deformation Analysis Of Deep-Mixing Pile Composite Ground

Deep-mixing pile has a number of merits, such as little disturbance, rapid construction and low cost. With the development of foundation engineering, the application of deep-mixing pile composite ground becomes wider and wider. However, the application and development of deep-mixing pile composite ground have been greatly confined by the insufficient theoretical studies and immature practice. Combining project based on indoor tests and field tests, the paper explored treatment effects of different field construction techniques on cement soil and the variation rule of mechanics properties of cement soil along with time. The relationship of loading force and that of deformation modulus between single-pile and multi-pile composite ground were summarized, the distributing rule of the stress of pile and soil at the bottom of cushion in the process of loading was explored, as well as a simplified calculational method concerning settlement in project was proposed. The main contributions are as follows:1. Physical and mechanical properties of cement soil generated by two field construction techniques, namely four-wing and six-wing, were analyzed through indoor tests. The mixing homogeneous degree of cement soil generated by these two construction techniques was compared, and the variation rule concerning modulus of compressibility and unconfined compression strength along with time was obtained.2. According to in-door tests result, the relationship concerning unconfined compression strength between field mixing cement soil and indoor mixing one with the same time was obtained.3. According to the result of loading tests, through comparing the bearing capacity and deformation modulus among single-pile, two-pile and four-pile composite ground, a conclusion was made that there exists group action in multi-pile composite ground and the loss coefficient of bearing capacity and that of deformation modulus were obtained respectively. Through comparison, it was discovered that the loss coefficient of bearing capacity is not equal to that of deformation modulus.4. According to the statistics in the loading tests, the stress distribution of pile and soil and the stress ratio between pile and soil at the bottom of cushion were analyzed, as well as the stress distribution chart and variation rule of stress ratio between pile and soil along with load were obtained. The soil pressure distribution at different positions under cushion of four-pile composite ground was compared, and the variation rule of both inner and outer soil pressure along with load was obtained.5. Combining Boussinesq solution, a calculational method with deformation modulus concerning the settlement of deep-mixing pile composite foundation was put forward on the basis of current research fruits.