软弱地层深基坑地基加固措施对比分析研究

研究目的：通过工程实践，进一步完善深基坑工程设计、施工和对周围环境影响控制等方面的技术和相关参数。 研究方法：结合上海地铁M8线Ⅲ标延吉中路车站和黄兴路车站深基坑地基加固的施工实践，采用方案设计→现场试验→监控量测→对比分析的方法，对软弱地层注浆加固和深层搅拌桩加固两种加固措施进行研究。 研究结果：在淤泥质软粘土中，双液注浆地基加固为劈裂效果，浆液成层状分布，在地下走向无规律，形成的加固体不均匀，均匀性较差，加固区对基坑连续墙变形未产生明显的抑制作用；水泥搅拌桩地基加固施工范围可控，水泥土较均匀，加固措施作用明显，有效约束了基坑的变形。 研究结论：双液注浆工艺控制及实施效果均不如水泥搅拌桩，但具有施工简便、造价低廉的优点。施工过程中，双液注浆工艺有待改善，应改一次注浆为二次注浆，同时提高二次注浆的注浆压力，提高加固土体的均匀性。

Comparative and Analytic Research on Reinforcement Technique for Foundation of Deep Foundation Pit in Weak Strata

Research purposes: The purpose was to improve the techniques and relevant parameters for design and construction of foundation of deep foundation pit,and control of influence on surrounding environment through engineering practice.Research methods: In combination with the engineering practice of reinforcing the foundation of deep foundation pits of Yanjizhong Road and Huangxin Road stations in Bidding III on M8 Line of Shanghai subway,the research was made on two techniques of grouting and deep-seated mixture pile to reinforce weak strata through scheme design,site experiment,monitoring,survey,comparison and analysis.Research results: Two-shot grouting was adopted to reinforce foundation in silt clay.The result of it was of crack with slurry distributing in layer and moving irregularly underground.The formed reinforced-body was not even with bad uniformity and the reinforced area had not distinctly restraint effect on the deformation of diaphragm of foundation pit.Cement mixture pile was adopted to reinforce foundation with good result of controllable working site,even cement-soil and effective restraining the deformation of foundation pit.Research conclusions: The technique and result of two-shot grouting were not good as that of cement mixture pile,but it had features of simple operation and low cost.The technique of two-shot grouting would be improved,such as changing grouting from primary grouting into secondary grouting,increasing grouting pressure of secondary grouting and improving uniformity of reinforced soil mass.