一种改进的位移释放率计算方法及其在Ⅴ级围岩中的应用

为了探究高地应力作用下Ⅴ级围岩的开挖卸载效应，针对隧道开挖过程中实时位移释放率难以计算这一问题，提出一种改进的位移释放率计算方法，对不同工法作用下Ⅴ级围岩的变形规律进行数值分析和模型试验研究。首先基于正交试验原理，以黄土、砂、石膏、水泥、水为原材料配置得到Ⅴ级围岩相似材料；然后以自行设计的模型试验箱为载体，对配制出的相似材料进行平行试验，以保证每组材料在改变一种原材料基础上其余材料均不变，从而得到各组材料的应变-时间变化曲线；最后利用改进的位移释放率计算方法，结合模型试验过程实时监测数据，得到Ⅴ级围岩不同开挖工法下的位移释放率变化曲线，并与数值分析结果进行对比验证。研究结果表明：配制出的围岩相似材料在物理力学性能上均能很好地满足试验需要且具有经济环保等优点；平行试验下，各组材料均对开挖卸载产生影响且石膏产生的影响最大；模型试验结果表明，开挖前期台阶法位移释放率最大，随着开挖的进行双侧壁导坑法位移释放率逐渐增大直至最大，模型试验所得位移释放率在数值上虽与数值模拟结果略有区别但整体趋势保持一致，两者均显示隧道开挖过程中CRD法的位移释放率最小且开挖后期位移释放率逐渐趋于平稳，故建议在该高地应力Ⅴ级围岩段隧道施工时全程采用CRD法。

Improved Calculation Method of Displacement Release Rate and Its Application in V-level Surrounding Rock

In this study,the authors proposed an improved calculation method of displacement release rate to explore the excavation unloading effect of grade Ⅴ surrounding rocks under the action of high ground stress,and carried out numerical analysis and model test research on the deformation law of gradeⅤ surrounding rocks under the action of different construction methods. The proposed method is aimed at solving the difficulty encountered when calculating the real-time displacement release rate in the process of tunnel excavation. First,based on the principle of orthogonal testing,similar materials to Ⅴ-Class surrounding rocks were obtained using loess,sand,gypsum,cement,and water as raw materials. Then,parallel tests were carried out on these materials to ensure that each group of materials changes one raw material and the rest remain unchanged,taking the self-designed model test chamber as the carrier. After which,the strain time curves of each group of materials were obtained. Finally,the improved calculation method of displacement release rate and the real-time monitoring data of the model test process were used. The change curve of the displacement release rate of Ⅴ-Class-surrounding rock excavation was obtained with different construction methods and compared to the results of numerical analysis. The results show that the materials can meet the requirements of the test and that they have the economic and environmental advantages. Under the parallel test,each material group had an impact on excavation and unloading,but gypsum possessed the greatest impact. The results of the model test show that the displacement release rate of the bench method is the largest in the early stage of excavation,and the displacement release rate of the double-sided heading method gradually increases to maximum as the excavation proceeds. Although the results of displacement release rate are slightly different from the numerical simulation results,the overall trend is consistent and they both show that the displacement release rate of the center cross diagram( CRD) method is the smallest in the tunnel excavation process and displacement release rate in the later stage of excavation. Therefore,the CRD method is suggested to be used in the whole process of tunnel construction in the Ⅴ-level surrounding rock section of the high ground stress.