LDP曲线数值求解中波浪形发展问题的解决

Solving the wave-shaped development in LDP curve numerical simulation

围岩纵剖面变形曲线(LDP,longitudinal displacement profile)是采用收敛-约束法进行地下洞室围岩支护设计的基础,针对数值模拟求解LDP曲线时存在的曲线形态波浪形发展变化所带来的围岩收敛位移难以准确把握的问题,从开挖步长与剖分精度的角度对解决这一问题进行了研究,同时分析了岩体开挖模拟方法、岩体自重设置对于围岩收敛变形的影响。结果表明:开挖步长对于围岩纵向变形曲线形态具有较大影响,选择不合适时会存在明显波浪形变化问题,求解LDP曲线时开挖步选择需要与数值计算网格剖分精度紧密结合;岩体开挖的模拟方式对于LDP曲线形态无影响,但对于围岩真实收敛位移具有较大影响;岩体自重对LDP曲线形态及围岩最终位移基本无影响。在求解实际工程LDP曲线时建议采用与网格剖分长度相等的开挖步长,此时对于LDP曲线形态及收敛绝对量值均无影响。研究成果可为地下洞室支护设计中围岩纵剖面曲线的求解提供一定的借鉴和参考。

The longitudinal displacement profile( LDP) of the surrounding rock is the foundation for the supporting design of underground caverns using the convergence confinement method. However,in the LDP curve calculation with general numerical simulation method,it is difficult to determine the converging displacement of surrounding rocks accurately because of the wave-shape development and variation of the curve. To solve this problem,studies were conducted based on the relationship between the excavation step size and the accuracy of the numerical calculation grid in this paper. And the effect of curve and converging displacement of surrounding rocks caused by excavation simulation method and setting of self-weight of rock mass were analyzed. The results showed that the excavation step size has a great effect on the shape of the longitudinal deformation curve of the surrounding rock. The inappropriate selection of the excavation step size may result in obvious wave-shapeed variation. The determination of the tunnel excavation step needs to be closely combined with the accuracy of the numerical calculation grid when solving the LDP curve. The simulation method of rock excavation has no effect on the shape of the LDP curve,but it has a great influence on the true convergence displacement of the surrounding rock.The self-weight of the rock has no obvious effect on the shape of the LDP curve and the final converging displacement of the surrounding rock. When solving the LDP curve of practical projects,it is recommended to use the same excavation step size as the mesh length,which has no effect on the LDP curve shape and the absolute value of convergence displacement of the surrounding rock. The results of this study can provide references for solving the longitudinal profile curve of surrounding rock in the design of underground cavity support.