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应用有限元方法模拟了软弱地基隧道锁脚钢管承受竖向集中荷载时的受力变形过程,研究了锁脚钢管的承载特性。锁脚钢管与围岩的接触压力主要分布在钢管外端很小区域,应力应变极值出现在钢管外端附近。随着荷载的增大,应力极值处首先进入塑性状态,钢管呈拔出破坏。对比分析了围岩强度和钢管参数对锁脚钢管承载力的影响规律,结论为:对于不能穿透软弱地基的锁脚钢管,其轴向承载力十分有限,合理下插角很小;常用的42 mm小导管直径过小,横向承载能力有限,不宜用作锁脚钢管;锁脚钢管存在一个决定于围岩强度和钢管规格的合理长度,超出合理长度后承载力不再增加;锁脚钢管应全长开孔注浆,重点加固初期支护结构附近的围岩。在此基础上,提出了锁脚钢管设计施工的方法和建议。
The finite element method was used to simulate the stress and deformation process of the tunnel steel tube of soft ground under vertical concentrated load, and the bearing characteristics of the steel pipe with the lock foot were studied. The contact pressure between the locking steel pipe and the surrounding rock is mainly distributed in a very small area outside the steel pipe, and the stress-strain extreme value appears near the outer end of the steel pipe. With the increase of load, the stress extremity first enters the plastic state, and the steel pipe is pulled out and destroyed. The influence of surrounding rock strength and steel pipe parameters on the bearing capacity of the lock-legged steel pipe is compared and analyzed. The conclusion is that the axial bearing capacity of the lock-legged steel pipe which can not penetrate the soft foundation is very limited and the insertion angle is reasonable. 42 mm small diameter of the catheter is too small, horizontal bearing capacity is limited, not suitable for locking the foot of steel; lock foot pipe there is a decision based on wall rock strength and the reasonable length of the steel pipe specifications beyond the reasonable length of bearing capacity no longer increases; Should be full-length grouting hole, focusing on reinforcing the surrounding rock near the initial support structure. On this basis, proposed the design and construction of locking steel pipe method and recommendations.