钢管压入土体施工挤土机制与案例分析

 对钢管压入土体过程中钢管内土塞的受力状态、产生挤土效应条件及挤土机制进行分析，结果表明：产生挤土效应的条件为土塞底部应力超过钢管端部地基承载力；根据土塞底部应力与钢管端部地基承载力的关系，不同情况下可认为钢管压入土体为非排土桩、排土桩及不完全排土桩；当为不完全排土桩时，挤土率可作为钢管压入过程中的挤土程度评价指标。对钢管内土塞底部应力与钢管端部地基承载力理论计算方法进行分析与总结。最后，通过钻孔灌注桩护壁钢管旋压施工工程案例的实测结果与实施效果，对钢管压入土体施工挤土机制理论分析的合理性与实用性进行论证。

ANALYSIS OF SQUEEZING MECHANISM FOR JACKED-IN CONSTRUCTION OF STEEL PIPE AND PROJECT CASE

Through the analysis of stress state of the soil plug，the condition of generating squeezing effect and squeezing mechanism for the process of jacked-in steel pipe is analyzed. The results show that：the condition of generating squeezing effect is that the stress at the bottom of the soil plug is greater than the bearing capacity of foundation at the end of the steel pipe；the jacked-in steel pipe can be regarded as displacement pile，non-displacement pile and incomplete displacement pile according to the relevance of the stress at the bottom of the soil plug and the bearing capacity of foundation；the extruding ratio can be used as the assessing index for the squeezing degree of the incomplete displacement pile. Besides，theoretical calculating methods for the stress at the bottom of the soil plug and bearing capacity of foundation at the end of the steel pipe have been analyzed and summarized. At last，through the measured data and implement result of the construction of the protective steel pipe for the bored pile，the rationality and practical applicability of the theoretical analysis for the jacked-in steel pipe have been demonstrated.