Research On Mechanism Of Cement Mixing Soil Strength Improvement And Practical Application In Offshore Engineering

Though deep cement mixing reinforcement technology has more obvious advantage in saving the reinforcing time and controlling the post-construction settlement, the strength of formation and growth of cement mixing reinforcement solids are affected by soil properties and environmental conditions, whose theoretical is far behind the engineering practice, therefore, the application in offshore engineering is not mature.Combining with deep cement mixing composite foundation reinforcement engineering, through indoor experiment, numerical simulation, field test and other methods to reveal the cement mixing reinforcement solids strength forming mechanism in the submarine soft soil and sea condition, in-depth study of optimum mix ratio and the main control factors of influence of reinforcement effect.。The research work includes:(1) studied the cement mixing reinforcement solids strength forming mechanism;(2) designed the cement-soil mixture ratio test by orthogonal test, a series of physical and chemical experiment had been carried out about the cement-soil mixture, the soil are silt, silt clay and silty clay which are taken from the Hong Kong-Zhuhai-Macao Bridge harbor east artificial island location and Tianjin Port Nanjiang port;(3) arranged and analyzed the experiment data, apply gray theory to study the most sensitive factors which affect the strength of cement soil;(4) applied numerical simulation method, combined with the tunnel engineering of deep mixing cement foundation reinforcement scheme of the Hong Kong-Zhuhai-Macao Bridge Island, used CDM method to compare and analyze the reinforcing effect before and after reinforcement at different ages;(5) combine the measured data of Tianjin Port Nanjiang Coal Terminal East approach bridge engineering, used the numerical simulation to reveal the validity of the CDM to control ground settlement and lateral deformation of the quay.Research shows that cement mixing method can change the marine soft soil physical and chemical properties, improve the soft soil structure and damage characteristics effectively which performed for the improvement of deformation and strength characteristics macroscopic. Indoor mixing ratio experiments show that the mixing solid density increases slightly compared with in situ soft soil; with the increase of water cement ratio, water content of cement soil increases however density decreases slightly, the permeability of cement soil improved significantly; cement soil strength varies with soil properties, silty soil is highest, silt, silt soil is relatively low, cement admixture affect the cement soil strength. Numerical simulation analysis shows that age of60d reinforced soil has been able to provide good bearing performance, using deep mixing technology in consolidation of marine soft soil can effectively control the vertical and horizontal deformation of foundation, while improving the anti sliding stability and bearing capacity.