Lei Mingfeng

Design Method of Slurry Volume–Weight in Trenching Construction of Underground Diaphragm Wall in Soft Stratum

Using the limit equilibrium analysis method, a global and a local stability mechanical models of trench wall in trenching construction of underground diaphragm wall were established, respectively, and the calculation formulas of critical slurry volume–weight, which can ensure the trench wall stable during trenching construction of underground diaphragm wall, were derived. And then, a design method of slurry volume–weight in trenching construction of underground diaphragm wall in soft stratum was formed, and also an application example was carried out. The results show that the design method of slurry volume–weight advanced in this paper is reliable, and in the similar projects (i.e., sand pebble stratum), the slurry volume–weight calculated by the local stability model of trench wall is more suitable.

Causes Analysis, Reinforcement and Repair Technology of Segment Crack and Damage During Shield Tunnelling Process: A Case Study

Segment crack and damage is one of the most common diseases in shield construction. Based on a practical project, the cause of crack damage, the safety of the damaged segment structure and its relative repairing technology were studied concretely by means of field investigation, numerical simulation and construction monitoring. The results show that the soil erosion, caused by water leakage in the project, is the main reason for the stress concentration and local crack of shield segments. At the same time, after grouting reinforcement inside and outside the tunnel and local segments repairing, there are no new cracks appear and develop, the monitoring indicators also tends to be stable, the segment structure is safe, and can meet the needs of subsequent process safety construction. It can be seen that the reinforcement and repair measures taken are effective and can be referenced for similar situations.

Study on Influence Factors of Crossing Railway Tunnel Excavation

In order to discuss the excavation influencing rule of crossing railway tunnel, 3 major influence factors including rock grade, cross angle and rock pillar height were taken into account, and 100 numerical models were designed for calculating, and then, the vault settlement and primary supporting internal force of existing tunnel induced by new tunnel excavation were analyzed. The study results show that: with the excavation processing of new tunnel, the vault settlement and primary supporting internal force of existing tunnel getting large, with the rock pillar height, cross angle and rock grade increasing, the increasing ratio of vault settlement of existing tunnel increases, but the increasing ratio of primary supporting internal force decreases, and with the cross angle increasing, the increasing ratio of primary supporting internal force increases.

Calculation of Surrounding Rock Pressure on Shallow Buried Tunnel Using Linear and Nonlinear Failure Criterion

Based on Terzaghi failure mode, calculation method of surrounding rock pressure on shallow buried tunnel was established using linear and nonlinear failure criterion, the modified Terzaghi theory which was extended to complex strata and the corresponding recurrence formulas for calculating vertical earth pressure was obtained by theoretical derivation. The surrounding rock in fractured zone of tunnel side wall was analyzed as isolated body by limit equilibrium method, and the explicit calculation expressions of horizontal earth pressure of shallow buried tunnel was obtained. Case analysis indicates that this method is feasible. And then, the effect of lateral pressure coefficient of overlying strata and nonlinear coefficient to surrounding rock pressure with linear and nonlinear failure criterion was further studied, the results show that the surrounding rock pressure decreases notably with lateral pressure coefficient of overlying strata increasing and decreases slowly with nonlinear coefficient increasing, and the effect of nonlinear coefficient to horizontal earth pressure is somewhat large.