单轴压缩下充填体损伤本构模型研究

Study on Damage Constitutive Model of Backfill Under Uniaxial Compression Loading

为了揭示充填体材料在单轴荷载下的损伤机理,首先对充填体材料在单轴荷载下的应力—应变曲线进行分析,再以损伤变量作为影响充填体材料力学特性的内变量,基于统计损伤理论、最大拉应力准则和应变等效假说,推导了充填体材料在单轴荷载下的经典损伤本构模型。由于充填体试件在初始阶段存在压密过程,提出了压密系数并将其引入到经典损伤本构模型,弥补了经典损伤本构模型无法合理解释充填体压密过程的缺陷。采用修正损伤本构模型对几种不同试验数据进行拟合,并与经典损伤本构模型进行对比,结果表明:拟合曲线不仅能够较好地模拟充填体试件在初始加载阶段的压密过程,而且拟合曲线与应力—应变试验数据基本吻合,充分说明所建立的修正损伤本构模型可靠性较好。为了进一步研究拟合参数变化对拟合曲线形状的影响,采用控制变量法改变其中一个参数,结果表明不同类型的拟合参数会对拟合曲线的形状产生不同的影响。

With the increasing emphasis on mine safety exploitation and the environment protection,filling mining method has been widely applied in many underground mines around the world.The damage and strength criterion of backfill is the most basic research content of filling mining and the research on the damage and strength of backfill is the most basic research content of backfill material.Thus,it is of great significance to the underground engineering to determine the mechanical properties and damage characteristics of backfill materials.In oder to reveal the damage mechanism of backfill material under uniaxial loading,firstly,the five successive stages of the stress-strain curves of backfill material under uniaxial loading were analyzed,such as initial compaction stage(OA),elastic deformation stage(AB),strain hardening stage(BC),strain softening stage(CD)and residual strength stage(DE),then taking the damage variable as the internal variable that affecting the mechanical properties of backfill materials,and the classical damage constitutive model of backfill material under uniaxial loading was derived based on the statistical damage theory,maximum-tensile strain yield criterion and strain equivalent hypothesis.Due to the backfill material contains a large number of micro defects such as micro pores and micro cracks,and there is a compaction process of the backfill specimen in the initial loading stage,a compaction hardening coefficient was proposed and introduced to the classical damage constitutive model and the modified damage constitutive model was established,which makes up the defects that the classical damage constitutive model cannot explain the compaction process of backfill in initial compression stage.The modified damage constitutive model was used to fit a variety of experimental data and was compared with the fitted results of the classical damage constitutive model.The results show that the modified damage constitutive model can not only simulate the compaction process of the backfill specimen in the initial loading process,but also be consistent with the stress-strain experimental data,and the fitting results are much better than those of the classical damage constitutive model,which fully indicates the feasibility of the modified damage constitutive model.The influence of the change of fitting parameters on the shape of the fitting curves was also studied and the control variable method was used to change one of the parameters to study the change trend of the shape of the fitting curves.The results of this study show that three different types of fitting parameters have different effects on the shape of the fitting curves.