支护时机对软弱围岩公路隧道力学特征影响的试验研究

Influence of supporting opportunity on stress characteristics of soft-weak surrounding rocks in highway tunnels

为了更全面地了解支护时机对软弱围岩公路隧道力学特征的影响,运用研制的地质力学模型试验简便实用的隧道开挖工具与方法,系统开展了基于先加载后开洞思路的公路隧道模型试验,研究了支护时机对软弱围岩公路隧道围岩压力、衬砌切向应力大小与分布规律的影响。试验结果表明:支护时机对软弱围岩公路隧道围岩压力、衬砌切向应力的大小及分布影响显著;在不同应力场的软弱围岩(原岩弹模为210 MPa)中开挖隧道,当开挖洞径为12 m左右时,200 mm左右的变形预留量是较为合适的。该工况下衬砌的切向应力、围岩压力均较小,而且各位置分布也比较均匀,对衬砌的受力最为有利。在实际工程中应加强监控量测,不断总结经验,尽可能地选择最佳时机支护以达到衬砌受力较小的目的。

In order to fully understand the influences of different supporting opportunities on the mechanical characteristics of soft-weak surrounding rocks in highway tunnels, the developed geomechanical model tests as well as the simple and practical tools and methods adopted in tunnel excavation are used. The highway tunnel model tests are systematically launched based on the idea of construction after loading. The influences of supporting opportunity on the surrounding pressure, the size and the distribution of shear stress of lining in soft-weak rocks in highway tunnels are studied. The results show that the influences are notable, and a 200 mm reserved deformation is reasonable when the excavation diameter is about 12 m under different stress fields in soft-weak surrounding rocks （the elastic modulus of surrounding rocks is 210 MPa）. Under such conditions, the shear stress and the surrounding stress are lower, and the distribution is also comparatively homogeneous, which is the most beneficial to lining force. In the actual project we should strengthen monitoring and measurement, sum up experience and choose the best opportunity to achieve smaller stress of lining as far as possible.