隧道施工防突岩盘破坏三维力学特征试验研究

Study on 3D Mechanical Characteristics of Outburst Prevention Rock-plate in Tunnel Construction

隧道施工开挖遇前方存在突水突泥致灾构造时,如隔水/隔泥岩土盘厚度小于最小安全岩土盘厚度时,隔水/隔泥岩土盘在致灾构造中地下水/黏土压力的作用下失稳破坏,致灾构造中地下水或致灾构造中黏土突出形成突水/淤泥灾害。本文采用隧道中最为常见的砂岩和灰岩制作长宽一定、厚度不同的完整和预设裂隙试件,进行集中荷载作用下的破坏试验,探索砂岩和灰岩防突岩盘三维力学特征及最小安全岩盘厚度和水头的联系。结果表明:砂岩岩盘破坏形成的裂纹呈“X”型,灰岩岩盘呈“树枝”型;砂岩岩盘裂纹沿尺寸较大的方向产生,存在原生裂隙时裂纹尖端向大尺寸方向扩展;灰岩岩盘裂纹沿着长对角线产生主裂纹,在裂隙较深处出现次生裂纹,裂纹主要沿一端进行扩展;随着长度的增加,完整砂岩岩盘最大横向应力呈现“驼峰”型曲线,裂隙砂岩盘最大横向应力呈现“山峰”型曲线,完整和裂隙灰岩岩盘最大横向应力呈现“单峰”型曲线,横向应力在某一长度时最大横向应力出现极值;随着厚度的增加,曲线最终呈现“单峰”型曲线,在某一厚度下,抗破坏力最强,砂岩和灰岩板破坏时的水头与厚度均呈幂指数的关系。

When there is a water-inburst and mud-induced structure in front of the tunnel construction and excavation,if the thickness of the water-repellent/mud-separated soil disk is less than the minimum safe rock-soil disk thickness,the water-repellent and mud-separated soil disk is unstable and damaged under the action of the groundwater/clay pressure in the disaster causing structure,and the groundwater or clay in the disaster causing structure is outburst to form the water inburst/silt disaster.In this paper,the most common sandstone and limestone in tunnels are used to make complete and prespecified fracture specimens with a certain length and width and different thickness.The failure tests under concentrated load are carried out to explore the three-dimensional mechanical characteristics of sandstone and limestone anti-outburst rock discs and the relationship between the minimum safe rock disc thickness and the head.The results show that the crack formed by the failure of sandstone rock disc is of"X"shape,and the limestone rock disc is of"branch"shape.The crack of sandstone disk is generated along the direction of large size,and the crack tip expands to the direction of large size when there is primary fracture.The cracks in the limestone rock disk produce primary cracks along the long diagonal,and secondary cracks appear in the deeper part of the cracks,and the cracks mainly expand along one end.With the increase of the length,the maximum transverse stress of the intact sandstone disc presents a"hump-shaped"curve,the maximum transverse stress of the fractured sandstone disc presents a"peak"curve,and the maximum transverse stress of the intact and fractured limestone discs presents a"unimodal"curve,with the maximum transverse stress appearing an extreme value at a certain length.With the increase of thickness,the curve finally presents a"single peak"curve.At a certain thickness,the anti-destructive force is the strongest.The relationship between the water head and the thickness of sandstone and limestone slab is power exponential.