低净空全套管灌注桩机研制及施工影响分析

针对常规全套管灌注桩机施工作业无法满足4 m以下低净空条件的问题，研制出一种能够解决因施工空间的限制导致无法进行全套管灌注桩施工问题的低净空全回转全套管灌注桩机，并进行了数值模拟和试桩施工影响分析。①通过改变钻进和取土方式，降低了设备机架高度及施工作业高度，实现了低净空全套管灌注桩施工作业；②通过试桩过程中孔隙水压力测试、深层水平位移监测、地表沉降观测和地下水位监测，明确了低净空全套管灌注桩施工对周围地层的影响范围；③通过数值模拟分析施工扰动，明确了实际下穿工程中低净空隔离桩的施工对既有桥梁结构的影响。研究结果表明:通过钻进和取土系统的结构创新，低净空全套管灌注桩机可以实现桐泾路北延隧道工程3.6 m极限高度下的隔离灌注桩的施工，且隔离桩施工基本不影响既有高铁桥梁结构的稳定与安全性。

Development of Low Clearance Full Casing Caisson Pile Machine and Analysis of Construction Influence

In order to break usage restrictions of routine full casing caisson pile under 4m clearance height, a type of low clearance full rotating full casing caisson pile machine is developed. Meanwhile relative numerical simulation and in-suit test of piles are processed to identify the influence of construction. ①The operation of low clearance full casing caisson pile is achieved by changing drilling and digging design, shortening height of equipment rack and max working altitude. ②Through monitoring pore water pressure, deep horizontal displacement, surface subsidence and underground water level, the influence area caused by construction of low clearance full casing caisson piles is revealed correctly. ③According to numerical simulation analysis of shelter piles construction disturbance during undercrossing project, the influence on existing bridge structure is analyzed and evaluated. The results of simulations and piling tests illustrate that the low clearance full casing caisson pile machine can realize drilling and digging operation of shelter piles under 3.6 m limited minimum height by structure innovation in Tongjing Road north tunnel undercrossing project, and then shelter piles construction won’t threaten the stability and safety of existing high-speed railway bridge structure.