顶管施工模型试验系统研发与应用

针对顶管施工产生的施工扰动问题和现有模型试验设备的不足,研发对管壁注浆压力、土仓压力和土体损失率能进行精确控制的室内顶管模型试验系统,并以海口给排水管网改扩建工程为背景,通过管线预埋的方式研究近间距顶管顶进对既有管道和地表竖向变形的影响.研究结果表明:研发的室内模型试验系统可以精确控制管壁注浆压力、土仓压力和土体损失率,试验系统得到的数据正确可靠;顶管顶进时会对既有管道产生附加应力,但附加应力远小于围岩应力,实际现场中无需考虑附加应力对管片承载的影响;现场顶进施工需对机头的切削速率和顶进速率进行协同调控,且严格控制出土速率,从而实现对地表竖向变形的有效控制.可为今后现场平行顶管施工提供有效指导.

Development and Application of Pipe Jacking Construction Model Test System

In view of the multiple rows of parallel pipe jacking construction disturbance problem and the deficiency of existing model test equipment, an indoor pipe-jacking model test system was developed to precisely control the grouting pressure of pipe wall, the pressure of soil bin and the soil loss rate. Based on the reconstruction and expansion of water supply and drainage pipe network in Haikou city, the effect of near distance pipe jacking on the vertical deformation of existing pipes and the ground surface is studied by means of pipeline embedding. The results of this test verified that the developed indoor model test system can accurately control the grouting pressure of pipe wall, the pressure of soil bin and the soil loss rate. The data obtained by the test system are correct and reliable; In order to select proper grouting pressure in actual site, it is necessary to realize vertical surface deformation control, that is, to coordinate with the cutting rate and jacking rate of the machine head, and to strictly control the excavation rate to balance the soil bin pressure and formation pressure. Pipe jacking produces additional stress on existing pipelines, but the additional stress is far less than the surrounding rock stress, so it is unnecessary to consider the effect of additional stress on the bearing capacity of pipe segments in the actual site. In the model test, the grouting pressure is reasonable, but the cutting rate of the machine head is not enough to guarantee, and the excavation rate is slow, which leads to the surface uplift all the time,these two parameters need to be further adjusted in subsequent tests.