【作者】 王大鹏；

【导师】 赵坚；

【作者基本信息】 东南大学 ， 岩土工程（专业学位）， 2020， 硕士

【摘要】 自然界的岩体内包含了大量的如节理、断层、层面等不连续结构面,这些不连续结构面使得岩体的力学性质与岩石有很大差异。研究表明,节理的力学特性对岩体强度以及稳定性有着至关重要的影响。在过去的几十年中,岩石力学、地球物理、地震工程的科研工作者对应力波入射节理岩体的各种情况进行了大量的理论和实验研究。现在的研究大多局限于一维状态下应力波垂直入射的情况,而自然界中倾斜入射的状况才是更为常见和普遍存在的。应力波倾斜入射节理岩体时,需要考虑节理的剪切变形特性。应力波倾斜入射一组平行节理时还涉及节理间的复杂反射,这些内容具有重要的研究价值,但是给相关的实验设计和数据采集带来了巨大的困难。考虑上述因素,基于其他科研工作者的相关理论分析,作者通过实验室二维物理模型超声试验,研究应力波倾斜入射一组线弹性节理时,节理数量和节理间距对应力波衰减规律的影响。随后,作者设计了不同节理起伏度的试样并与其他研究人员的理论研究作对比,尝试研究高应变率下应力波以不同角度入射后岩体的破坏规律。岩体结构的稳定性评估通常是基于应力、位移、速度、加速度等临界值做出的。在超声波作用下节理变形处于弹性状态,同时,由于超声波频率较高,节理间距和波长的比值较大,因此超声实验主要关注应力波幅值衰减以及波速的变化,对高应变率非线性变形状态的节理则主要关注其破坏强度。当超声波入射一组节理时,时域结果具有更高的精确度,但可能受到试样与测量仪器耦合及边界的反射波的影响,实际测得的时域内数据在某些情况下是复杂叠加后的结果,因此使用频谱分析的方法对时域透射波进行处理,剥离出未经叠加的频域初始波,在频域范围内分析应力波透射规律,本文将同时在时域及频域内对应力波倾斜入射节理后的幅值衰减进行计算分析。超声波倾斜入射节理岩体时,节理变形保持弹性状态,但是在地震、冲击荷载、爆炸作用等高应变率动力问题下,岩体发生破坏,超声模型的试验结果不再适用,作者设计不同节理起伏度试样,主要关注冲击荷载下节理岩体的破坏强度,通过测量多组不同节理起伏度试样破坏强度积累以插值法评估任意不规则单节理面的基础数据,并将其应用于工程中常见的应力波倾斜入射节理的实践中。本次超声实验通过时域与频域的分析结果,证明了应力波倾斜入射一组平行节理时,应力波幅值随着节理数量的增加而减小,随着节理间距的增大,应力波幅值先增大后减小,本次实验还揭示了根据初始波持续时间来推断特定岩体内节理分布情况这个具有重要实践意义的结论。本次实验的结果与一些学者使用等效介质法、虚拟波源法的理论解有较高的吻合度,验证了等效介质法和虚拟波源法研究应力波倾斜入射一组平行节理的可行性,同时,对于节理起伏度的创新性研究,可以给其他科研工作者一些启发。更多还原

【Abstract】 Natural rock mass contains many discontinuous structural surfaces such as joints,faults,and layers.These discontinuous structural surfaces make the mechanical properties of the rock mass different from those of the rock.Research results show that the mechanical properties of joints have a vital influence on the strength and stability of rock mass.In the past decades,researchers in rock mechanics,geophysics and seismic engineering have done a lot of theoretical and experimental research on various cases of stress wave propagating across joints.Most of the studies are limited to the case of the stress wave incident vertically,which is one-dimensional case,while the case of oblique incident in nature is more common.When stress waves oblique incident on a rock joint,the shear deformation characteristics need to be considered.Besides,complex reflections between joints need to be considered when stress wave incident a set of joints.These contents are of great value but also bring great difficulties to relevant laboratory experiment design.Considering the above factors,the purpose of this laboratory experiment is to study the effects of the number of joints and the spacing of joints on the stress amplitude attenuation and the velocity attenuation.Meanwhile,the effect of different incident angles under high strain rate will be studied by designing samples with different joint undulation.The stability assessment of rock mass structure is based on critical values such as stress,displacement,velocity,and acceleration.The joint deformation of rock joints is in an elastic state with ultrasonic wave.Meanwhile,due to the high frequency of ultrasonic wave,the ratio of joint spacing to wavelength is large,therefore the ultrasonic experiment mainly focuses on the attenuation of stress amplitude and wave velocity.while the failure strength of joints in the nonlinear deformation state with high strain rate is the key point.When ultrasonic wave incident into a set of joints,the time domain results have higher accuracy,but it can be influenced by coupling effect within sample and measuring instrument,the actual measured data in time domain is a result of complex superposition.With spectrum analysis,initial wave can be stripping in frequency domain without superposition.This article will calculate amplitude attenuation in both time domain and frequency domain.Joint deformation keeps elastic state under ultrasonic wave,but in high strain rate dynamic problem as the earthquake,explosion,impact load function,rock mass damage occurs,the test results of ultrasonic model is not valid.The author designed samples with different joint undulation to study the strength of joint rock mass under the shock load.The basic data of interpolation method is accumulated by measuring the failure strength of multiple groups of samples.Test result s will be applied to stress wave oblique incidence of joints in common engineering practice.The results of this ultrasonic experiment are in good agreement with the theoretical solution of effective medium theory and virtual wave source method,which proves the feasibility of theoretical solution in study stress wave incident in a set of parallel joints.This experiment also reveals a conclusion of practical significance to predict the joint distribution of a particular rock mass based on the duration of the initial wave.The innovative research on joint undulation can give some inspiration to other researchers.更多还原