3洞小净距隧道围岩压力计算方法

针对3洞小净距隧道围岩压力计算问题,基于普氏平衡拱理论,将围岩压力看作单洞隧道的基本压力与相邻隧道开挖引起的附加压力之和,提出适用于3洞小净距隧道的围岩压力计算方法;根据该计算方法研究不同岩柱厚度、开挖跨度和开挖高度对围岩压力的影响规律,并将该计算方法应用于确定八达岭长城站3洞小净距隧道围岩压力。结果表明:随着岩柱厚度的增加,围岩压力不断减小,当岩柱厚度达到某一值时,围岩压力与单洞隧道相同;岩柱厚度、边洞跨度和中洞高度变化影响整体围岩压力,中洞跨度和边洞高度仅影响各自单洞围岩压力;3洞小净距隧道的最优开挖顺序为"先边洞、后中洞",中洞围岩压力大于边洞,应力值最大点为中洞顶部。施工中应注意中洞围岩稳定,采取有效的措施对岩柱区域进行加固。

Calculation Method for Surrounding Rock Pressure of Closely Spaced Triple Tunnels

For the calculation of the surrounding rock pressure of closely spaced triple tunnels, based on the Protodyakonov’s theory, the surrounding rock pressure was regarded as the sum of the basic pressure of the single-hole tunnel and the additional pressure caused by the excavation of the adjacent tunnel. The calculation method of the surrounding rock pressure suitable for closely spaced triple tunnels was put forward. According to this calculation method, the influence of different rock pillar thicknesses, excavation spans and excavation heights on the surrounding rock pressure was studied. The calculation method was applied to determine the surrounding rock pressure of closely spaced triple tunnels in Badaling Great Wall Station. Results show that with the increase in the thickness of rock pillar, the surrounding rock pressure decreases continuously. When the thickness of rock pillar reaches a certain value, the surrounding rock pressure is the same as that of a single-hole tunnel. The variations in rock pillar thickness, side tunnel span and middle tunnel height affect the overall surrounding rock pressure, while the middle tunnel span and side tunnel height affect the surrounding rock pressure of each single tunnel only. The optimal excavation sequence of closely spaced triple tunnels is"first side tunnel, then middle tunnel". The surrounding rock pressure of the middle tunnel is greater than that of the side tunnel, and the maximum stress value is at the top of the middle tunnel. During the construction, attention should be paid to the stability of the surrounding rock of the middle tunnel, and effective measures should be taken to reinforce the rock pillar area.