基于剪切和张拉试验的水泥砂浆–黏土岩二元体界面影响区模型

An interface influence zone(IIZ)model of cement mortar-clay rock binary based on shear and tension tests

黏土岩隧道常采用喷射水泥砂浆的方法进行初次支护,若支护与岩体黏结强度不足将产生巨大的安全隐患。以水泥砂浆–黏土岩二元体为研究对象,开展界面的剪切和张拉试验,首先分析黏土岩初始含水率对二元体黏结强度的影响,然后根据二元体的宏观破坏模式和细观的孔隙特征,提出一种确定界面影响区厚度的方法,最后建立界面影响区模型,进行偏压状态下界面脱黏的数值模拟。研究表明:(1)张拉和剪切破坏时,砂浆–黏土岩二元体的破坏面均位于浇注界面附近的黏土岩中,该区域的力学性能较差,为二元体的界面影响区。(2)二元体界面抗剪刚度Ks和残余摩擦因数k与法向应力无关,随含水率增加而减低。(3)二元体浇注过程中浆液向黏土岩渗入和水泥凝结过程中水分向砂浆侧的迁移会引起黏土矿物的胀缩,在影响区内产生大量的初始微裂隙,根据这一特殊的孔隙特征,基于计算机层析扫描(CT)和数字图像处理技术,可以对影响区厚度进行无损伤识别。(4)本文提出的界面黏结模型,考虑了界面在法向和切向的黏结效应及切向的摩擦效应,可以准确地模拟二元体张拉及剪切破坏时的应力–位移关系。(5)当界面处于偏压状态时,砂浆–黏土岩界面的脱黏荷载随荷载与界面法线夹角的增大而较小,因此偏压隧道的支护结构更易脱黏,施工时宜采取加强措施。

Spraying cement mortar is often used in the construction of supporting structures in clay rock tunnels.The debonding of the interface may induce serious geology hazards.Taking the cement mortar-clay rock(C-C)binary as the research object,the shear and tension tests of the interface are carried out.Meanwhile,the influence of the initial moisture content of clay rock on the cohesive strength of the binary is analyzed.According to the macroscopic failure mode and microscopic pore characteristics of the binary,a method to determine the thickness of the interfacial influence zone is given.A new numerical model of C-C binary is proposed,which can simulate the effect of the interfacial influence zone.Finally,the debonding process of eccentric compression binary was taken by the new numerical method.The results show that:(1)In shear or tension tests,the failure face of the mortar-clay rock binary is located in clay rock near the interface,which is a weak zone of the binary,namely the interfacial influence zone(IIZ).(2)The shear stiffness Ks and residual friction coefficient k are independent of normal stress and decrease with the increase of water content of clay rock.(3)The infiltration and solidification of cement slurry will cause the swelling and shrink of clay rocks near the interface,which will produce a large number of initial micro-cracks in the interfacial influence zone.Based on the special pore characteristics of the interfacial influence zone,the thickness of the zone can be identified and measured by computer tomography(CT)and digital image processing technology.(4)The new interface cohesive model considers the bonding effect in the normal and tangential direction and the friction of the interface at the same time,which can simulate the stress-displacement relationship of binary accurately.(5)When the interface stays in an eccentric compression state,the debonding load decreases with the increase of the angle between the load and the interface normal.Therefore,the support structure of the eccentric compression tunnel is more prone to debonding.