地下洞室三维弹塑性动力显式有限元锚杆模拟  

Simulation of anchor bolts by explicit 3D elastoplastic dynamic finite element method for underground caverns

作　　者：张志国[1] 肖明[1] 

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,武汉430072

出　　处：《水力发电学报》2012年第4期181-188,206,共9页Journal of Hydroelectric Engineering

基　　金：国家自然科学基金重大研究计划(90715042);国家杰出青年科学基金(50725931);国家科技支撑计划(2008BAB29B01);中央高校基本科研业务费专项资金

摘　　要：锚杆的数值模拟方法是分析地震灾变中锚杆的作用机理及锚杆支护对地下洞室围岩抗震的加固效果的关键。基于地震动荷载作用下锚杆围岩联合受力机理,在对FLAC3D锚杆模拟算法进行一定改进的基础上,提出了一种适用于抗震分析的全长粘结式锚杆模拟方法,并将该方法应用到自主开发的地下洞室三维显式动力有限元程序中,取得较好效果。该方法继承了FLAC3D中对锚杆、锚杆与砂浆接触面、锚固砂浆、砂浆与围岩接触面及围岩本身共5种结构材料的受力破坏情况的详细模拟,但不再进行相邻锚杆计算段之间的受力平衡迭代,而是将各锚杆计算段的受力转移到单元结点上,将锚杆求解与单元求解相统一,从而降低动力求解中锚杆的计算耗时。同时,详细推导了锚杆各结构材料的屈服极限表达式,缩短了锚杆结构材料屈服判断及应力修正耗时。该锚杆模型与FLAC3D中的模型假定不同,认为锚杆变形由围岩变形引起,各锚杆计算段间受力相对独立,受力并不连续,与地震中围岩锚杆的受力情况较吻合。采用该方法对某地下厂房洞室群进行地震动力时程分析,表明该模拟方法提高了求解速度,充分反映了锚杆对围岩的支护效果。Numerical simulation method of anchor bolts is mechanism of anchor bolts and their reinforcing effects in a key issue for understanding the working analysis of the seismic disaster process of underground caverns. Based on the joint loading mechanism of anchor bolts and surrounding rock under earthquake impact, the numerical algorithm of anchor bolts adopted by FLAC3D is improved and a new algorithm, suitable for the aseismic analysis, is proposed to simulate fully-grouted anchor bolts. This new algorithm was implemented through an independently-developed explicit 3D elastoplastic dynamic FEM code, and satisfactory results were obtained. This method takes advantages of FLAC3D algorithms for simulating five types of damage under loading conditions, i.e. anchor bolts, anchor-bolts contacting mortar, anchor mortar, mortar contacting surrounding rock, and surrounding rock. It transfers the force bear by each computation section of anchor bolts to the FEM nodes, rather than iterating for loading equilibrium. Thus, it unifies the solution of anchor bolts and elements and reduces the computational cost of anchor blots in dynamic analysis. Moreover, analytical expressions of yield limit for various types of anchor bolt materials are derived in details, which leads to a cost saving in yield state determination and stress modification. The proposed anchor bolts model adopts an assumption different from those of FLAC3D model, i.e. the deformation of anchor bolts is induced by the deformation of surrounding rock. Under this condition, the force bear by each section of anchor bolts is independent from each other, and the forces along an anchor bolt are not continuous. This assumptionagrees with the real earthquake process. A dynamic analysis case study for a practical underground cavern indicates that the proposed method enhances the computation speed and fully reflects the supporting effects of anchor bolts to surrounding rock.

关 键 词：岩土力学 锚杆模拟 显式有限元 地下洞室 

分 类 号：TU443[建筑科学—岩土工程]