NPR锚索对跨断层软岩大变形隧道控制技术研究

Control Technology of Negative Poisson′s Ratio Anchor Cable for Large Deformation Tunnel Across Faulted Soft Rocks

为探究NPR锚索对东马场跨断层软岩大变形隧道控制效果,首先对NPR锚索进行静力拉伸试验,验证其恒阻大变形的能力和具有良好的抵御外力的效果;随后开展NPR锚索对东马场隧道围岩变形控制的三维物理模型试验。试验现象和数据表明:在开挖过程中,隧道围岩也没有出现较大垮落和坍塌,NPR锚索对软岩隧道围岩有较好的支护效果。在加载完成后,NPR锚索对非断层处的隧道围岩最大位移约为14 mm,断层处的围岩最大位移约为21 mm,隧道区域所受应力分布的不规律性,导致隧道围岩出现挤压变形,位移曲线呈振荡状。在NPR锚索的支护下,围岩应力最大发生在左拱肩,围岩临空面3 cm处切应力最大(0.3 MPa),隧道未出现大规模的不对称破坏现象,隧道总体呈现出“小塌而不垮”,变形总体可控。

To investigate the control effect of negative Poisson′s ratio(NPR)anchor cable on large deformation of Dongmachang tunnel in soft rock across faults,static tensile experiments are conducted on the NPR anchor cable to validate their constant resistance to large deformations and their effectiveness in resisting external forces.Subsequent experiments on three-dimensional physical modeling of NPR anchor cable for deformation control of the surrounding rock in the Dongmachang tunnel.The experimental phenomena and results show the following:(1)In the excavation process,the tunnel surrounding rocks exhibit no large collapse,indicating that the NPR anchor cable has a better support effect on the soft rock tunnel surrounding rocks.(2)After loading,the maximum displacement of the surrounding rock at non-faulted section after using NPR anchor cable is approximately 14 mm,and that at faulted section is approximately 21 mm.The irregularity of the stress distribution applied to the tunnel area leads to extrusion and deformation of the tunnel surrounding rock with an oscillating displacement curve. (3) Under the support of NPR anchor cable, the maximum surrounding rock stress occurs at the left arch shoulder, and the maximum shear stress occurs at 3 cm on free face (reaching 0.3 MPa). Large-scale asymmetric damage does not appear in the tunnel, and the general deformation can be controlled.