排桩锚杆复合土钉作用机制的试验研究与分析

本文结合某基坑工程,采用分布式光纤测量技术配合应力计监测土钉和预应力锚杆的应力分布、轴力变化,研究了基坑开挖过程中土钉和预应力锚杆的应力应变随工况发生变化的规律、注浆效应对土体力学参数及其对基坑潜在滑裂面变化的影响。得出主要结论:在试验条件下,预应力锚杆轴力随开挖深度增加而增加,开挖完成后随时间变化,预应力锚杆轴力逐步减小、土钉轴力逐步增加,锚杆与土钉承载力发挥难以协调,降低了总的安全度;未考虑排桩插入深度对支护的作用,是导致预应力锚杆和土钉轴力较小的原因,排桩复合土钉应考虑排桩的支护作用。通过对排桩预应力锚杆复合土钉支护体系的受力变形分析,提出了该支护设计的建议,对类似工程的设计和施工有着重要的指导意义。

Experimental study and analysis on mechanism of composite retaining structure of soldier pile with prestressed anchors and soil nails

The stress distribution and axial force change is monitored by distributed optical fiber sensing technology and stress gauges in a foundation pit excavation project. The stress and strain changing rule of soil nails and prestressed anchors, the influence of grouting to soil mechanical parameters and the change of potential failure surface of the pit are studied. It is concluded that the tensile force of prestressed anchor increases with the increasing of excavation depth, and after the completion of the excavation, it decreases over time, while the tensile force of soil nail increases gradually. Hence, the bearing capacity of prestressed anchor and soil nail cannot be coordinated, which decreases the safety of pit excavation. Moreover, the retaining effect of soldier pile should be taken into account in design, otherwise it would result in smaller tensile forces of prestressed anchor and soil nail. Based on the aforesaid analysis, some advises on the design of the composite retaining structure are brought forward, which would provide a guide to the similar project.