基于多孔弹塑性模型的软弱泥质页岩隧道建模与模拟

Modeling and simulation in soft argillaceous shale tunnel based on porous elaso-plastic model

针对泥质页岩多孔、遇水易分解的岩性,基于剑桥粘土模型,建立了一个涉及多孔岩土材料的弹塑性本构模型,并数值模拟了某软弱泥质页岩隧道的力学行为。从混合理论出发,把泥质页岩体看成一个由固体(土)-流体(水)-气体(气)组成的三相混合体,引入有效应力的概念,建立了一个适用于工程实践的本构模型,该本构准则反映了有效应力与固相矩阵形变之间的发展方程、饱和度与吸力之间的关系方程以及液相和气相状态下,相关联的流动法则与固有压力的发展方程。开发了基于FORTRAN语言的大型有限元计算程序以及适用于泥质页岩多孔弹塑性土体的POROSTONE材料子程序,对某软弱泥质页岩隧道进行了数值模拟,并与现场实测数据进行了比较分析。研究结果表明:该多孔弹塑性模型能较为真实地反映泥质页岩土体遇水易分解的特性;围岩变形在前期的变形速率很快,在后期变形的速率减缓,但稳定下来的时间也比较长;泥质页岩隧道两侧拱脚处的围岩压应力较大,应当加强辅助措施在施工中的应用,尤其适宜加设锁脚锚杆以改善型钢支护的受力状态。

On the basis of Cam-clay Model,a proposal constitutive model on porous elaso-plastic geo-material was derived for the argillaceous shale,which was porous and easy to decompose with water,and then the mechanical behavior in an argillaceous shale tunnel was simulated.According to the mix theory,the argillaceous shale was analyzed as a three-phase mixture coupling with solid-liquid-air,and the effective stress was introduced to set up a proposal constitutive model.The constitutive laws relate： the evolution of the constitutive effective stress with imposed solid matrix deformation,the degree of saturation with suction stress,and the relative flow vector with intrinsic pressure for the water and air phases.Based on the FORTRAN language,a Finite Element Method program was coded,with a material subroutine named POROSTONE for the argillaceous shale elaso-plastic model,and then a soft argillaceous shale tunnel was simulated.At last,a compared analysis was derived with the data in-situ.Some results are revealed as follows： the porous elaso-plastic model works well and are in good agreement with the measured data in-situ;the deformation velocity is fast during the prophase of the tunnel excavating,compared with the later,but the steady time is long;some assistant measures,especially the lock-foot anchor should be set to enhance the steady state due to the bigger compressive stress located at the arch foot of the two sides in the tunnel.