基于松动圈理论深埋黄土隧道围岩压力计算方法

围岩压力的确定一直是隧道工程结构设计中的重点,而黄土隧道的工程特性与其他岩质隧道有着明显的区别,尤其是深埋黄土隧道的围岩压力计算。通过对深埋黄土隧道开挖后的围岩应力状态进行分析,明确了松动圈的定义,推导了松动圈的表达式,提出了基于松动圈理论的深埋黄土隧道围岩压力计算方法,并基于现场试验实测数据与既有计算方法进行了对比分析,以验证该方法的适用性。研究结果表明：松动圈为塑性区的内圈,是塑性区内切向应力小于初始地应力的部分；黄土隧道的松动圈较普通巷道和岩石隧道的松动范围大得多,更易受隧道开挖影响；基于松动圈理论的围岩压力计算方法与其他计算方法相比较,计算结果与实测值接近且存在一定的安全储备,使用该方法对深埋黄土隧道围岩压力进行计算是可行的,基于松动圈理论的围岩压力计算方法更适用于深埋黄土隧道这种有一定自稳能力的软弱土质围岩隧道。

A Method for Calculating Surrounding Rock Pressure of Deep Loess Tunnel Based on Loose Broken Rock Zone Theory

The determination of surrounding rock pressure has always been the focus in the structural design of tunnel engineering, and the engineering characteristics of loess tunnel cause the determination of its surrounding rock pressure to be significantly different from other rock tunnels, especially deep-buried loess tunnels. By analyzing the stress state of the surrounding rock after excavation in deep loess tunnels, the definition of loose broken rock zone is defined, and the calculation formula of the loose broken zone of the surrounding rock is deduced. A method for calculating the surrounding rock pressure of deep-buried loess tunnels based on the loose broken rock zone theory is put forward. Based on the field test data, the applicability of the method is verified by a comparative analysis with the existing calculation method.The results show that the loose broken rock zone is the inner part of the plastic zone, which is the part where the tangential stress in the plastic zone is less than the initial ground stress. The broken rock zone of loess tunnels is much larger than that of ordinary roadways and rock tunnels, indicating that the loess tunnel is more susceptible to tunnel excavation. The calculation results of the proposed method are closer to the measured value of loess tunnels than that of other calculation methods and it is able to provide better safe allowance to some degree. Thus, the calculation of the surrounding rock pressure of deep-buried loess tunnels with the broken rock zone theory is feasible. It is more suitable for the soft surrounding rock of deep buried loess tunnel with certain self stability.