土压平衡盾构施工模块化分步缩尺模型试验设计与应用

Design and application of modular step-by-step scale model test for earth pressure balance shield construction

为提高对盾构施工相关问题试验研究的针对性,提出了土压平衡盾构施工模块化分步缩尺模型试验方法,并设计了模型试验相关装置;为避免多个关键影响因素相互影响,将盾构隧道施工过程中开挖掘进、管片拼装、同步注浆等关键操作环节分开依次进行模拟;为降低刀盘开口率试验研究相关成本,研制了几何相似比为1∶10且刀盘开口率可调的模型盾构机;为确保模型盾构隧道的纵、横向刚度相似性,设计了几何相似比为1∶10且纵、横向刚度可分别按需设置的模型盾构隧道,其管片环采用修正匀质圆环模型,管片环之间采用垫有压缩弹簧的螺栓连接;为方便试验并节省成本,模型盾构隧道采用外部拼装后再放入钢套筒内,以避免在狭小空间内进行管片拼装,且不加工管片拼装机;为实现注浆压力与注浆量的精准控制,设计了适用于室内模型试验的恒压同步注浆装置;利用模型盾构机开展了掘进施工过程中渣土输出控制对地表沉降影响的试验研究。分析结果表明:单位掘进距离的渣土输出量直接关系到盾构掘进过程中的超挖控制,从而影响地表沉降,当出土率小于1时,出土率变化对地表沉降影响较小,当出土率大于1时,出土率增大将显著加大地表沉降。为了最大程度地发挥整个模型试验的科研价值,在盾构隧道完成施工后,建议继续开展盾构隧道响应研究的相关模型试验。

To improve the pertinence of experimental research on shield construction-related problems,a modular step-by-step scale model test method for the earth pressure balance shield construction was proposed,and the model test-related device was designed.To avoid the mutual influence of multiple key influencing factors,the key operation links for the shield construction such as the excavation,segment assembly,and synchronous grouting were simulected in a separate and sequential manner.To reduce the cost of experimental research on the cutterhead opening rate,a model shield machine with a geometric similarity ratio of 1∶10 and an adjustable cutterhead opening rate was developed.To ensure the similarity of the longitudinal and transverse stiffnesses of the model shield tunnel,a model shield tunnel with a geometric similarity ratio of 1∶10 and the longitudinal and transverse stiffnesses set on demand respectively was designed.The segment ring adopted the modified homogeneous ring model,and the segment rings were connected by compression spring bolts.To facilitate the test and save the test cost,the model shield tunnel was assembled externally and then put into the steel sleeve,so as to avoid the segment assembly in a narrow space,and the model shield machine did not need to process the segment assembly machine.To realize the precise control of grouting pressure and grouting amount,a constant pressure synchronous grouting device suitable for the indoor model test was designed.The experimental study on the influence of slag soil output control on the surface settlement during the tunneling construction was carried out by using the model shield machine.Analysis results show that the slag soil output per unit tunneling distance is directly related to the over-excavation control in the process of shield tunneling,thus affecting the surface settlement.When the unearthed rate is less than 1,the change in the unearthed rate has little effect on the surface settlement.When the unearthed rate is greater than 1,the increase in the unearthed rate will significantly increase the surface settlement.To maximize the scientific research value of the whole model test,it is suggested to continue to carry out the relevant model test of shield tunnel response research after the completion of shield tunnel construction.