Study And Application On Deep-mixing Pile Composite Ground And Curtain For Cutting Off Water

Deep-mixing technique is one of common ground improve methods and widely used in composite foundation and curtain for cutting off water. On the basis of former research achievements of other scholars and also combined with practical engineering requirements, the following results with in-situ tests and theory analysis were obtained.(1) The measure of improving strength of deep-mixing pile was proposed after main influence factors on strength of cement-soil and deep-mixing pile were analyzed using research results of other scholars.(2) Comparison and analysis on load tests in composite ground of single and multi-piles of spout powdered piles show that basic value of bearing capacity and deformation modulus of composite ground decrease with increase of the number of piles in load test and that settlement increases obviously with increase of the number of piles in load test under same-class load. Based on the results of composite ground load tests, the pile group effect coefficient of compressive modulus of deep-mixing pile composite ground was given.(3) Numerical model of composite ground of single and multi-piles of deep-mixing piles was built using finite-difference method. Using program FLAC3D, the distribution of stress and displacement of deep-mixing pile composite ground was obtained.(4) The settlement calculation method of deep-mixing pile composite ground was studied. The ideas to realize optimization design of composite ground through computing minimum value of total pile length in composite ground was proposed after main influence factors on engineering price of composite ground were discussed. Mathmatic model of optimization design of deep-mixing pile composite ground with rectangle foundation under axial load was built. Using length of single pile and pile distance as variable, the calculation formulas of optimization design of deep-mixing pile composite ground were deduced, and the calculation program was coded The main factors which affect the total pile length were analyized and some suggestions of optimization design were proposed.(5) In the design of curtain for cutting off water in deep-mixing piles, it is proposed that there is waste of cement content calculated by traditional formula of cement-mixed proportion. Calculation formulas of cement-mixed proportion and thickness of curtain for cutting off water in deep-mixing piles were deduced. The good effectiveness and economical benefit are achieved after practical engineering application.(6) The problem of water leakage from curtain for cutting off water is reasonably solved after the conception of apparent connection width and construction method of big connection width in curtain for cutting off water in deep-mixing piles are proposed from practical engineering need. The economical benefit of the construction method of big connection width is better than that of construction method of traditional connection width.(7) The difficult of narrow construction site is successfully solved after the design method and construction technology of support and water cut-off technique for the foundation pit with bored piles drilled in single-row deep-mixing piles of curtain for cutting off water are proposed in the narrow available site of the underground.