不同岩石抗拉与抗压实验对比研究

发布时间：2018-04-05 04:28

本文选题：抗拉　切入点：抗压　出处：《南京大学》2014年硕士论文

【摘要】：由于岩石属于典型的脆性材料,其能够承受的抗拉强度远小于抗压强度,这使对于岩石抗拉性能的研究变得很重要。要研究岩石在拉伸状态下的各种属性,首先要获得岩石在拉伸状态下的各种力学参数,主要包括抗拉强度、弹性模量和泊松比等。要获得岩石拉伸状态下的力学参数最直接的方法便是通过岩石力学室内试验进行测量。通过对现有文献资料的查阅,不难发现,岩石的拉伸试验不像岩石压缩试验只有单轴压缩试验一种那么单一,而是存在着直接拉伸、巴西劈裂、三点弯曲、圆环破裂和水压致裂等多种试验方式,而且尤以巴西劈裂试验用的最为广泛。产生岩石拉伸试验多种试验方法林立现状的原因无非是在相当长的一段时间内,受粘结剂和试验机的限制实现岩石的直接拉伸相当困难,所以广大学者通过其他试验方法,绕开了直接拉伸试验实现的难点,间接求取了岩石的抗拉强度。但同时我们也注意到,随着岩石力学试验方法的发展和进步,已经有很多学者成功的进行了岩石的直接拉伸试验,通过对他们试验方法的研究,结合现有试验仪器,做出一些合理的改进后,本研究中同样能够成功的进行岩石的直接拉伸试验,且试验结果令人满意。这便为获得最可靠的岩石拉伸力学参数提供了保证。但同时发现很多情况下因为试验仪器的限制,实现岩石的直接拉伸试验尚不易,但若对岩石直接拉伸试验和间接拉伸试验做出对比研究则可以以直接拉伸试验中真实的岩石拉伸试验指标对比岩石间接拉伸试验中的拉伸指标,从而发现两者的异同,为因试验条件限制而无法进行岩石直接拉伸试验的情况做参考。选择了4种比较有代表性的岩石(曲阳花岗岩、大理岩、北山花岗岩、灰岩)含盖了3大岩类,分别制成满足试验需求的标准试样,分别进行了单轴压缩、直接拉伸、巴西劈裂和三点弯曲试验,得到其在拉伸(包括直接拉伸和间接拉伸)和压缩下的强度变形参数。通过对拉伸和压缩强度和变形参数的分析,首先通过三大强度准则,推导了巴西劈裂间接拉伸试验抗拉强度和直接拉伸试验抗拉强度差异性的原因。同时发现岩石在这两种受力情况下的变形参数(弹性模量、泊松比)差异非常大,对此根据试验结果采用FLAC3D数值分析软件,比较了在考虑拉伸和压缩下岩石不同性质的前提下,巴西劈裂试验方法数值模拟结果和理论计算结果的差异。
[Abstract]:Because rock is a typical brittle material, its tensile strength is much smaller than that of compressive strength, which makes the study of rock tensile properties very important.In order to study the properties of rock under tensile condition, the mechanical parameters of rock under tensile condition, including tensile strength, elastic modulus and Poisson's ratio, are obtained.The most direct way to obtain the mechanical parameters of rock under tensile condition is to measure the mechanical parameters through the laboratory test of rock mechanics.It is not difficult to find that the tensile test of rock is not as single as the uniaxial compression test of rock, but there is direct tension, Brazil splitting, three point bending.There are many kinds of test methods, such as ring rupture and hydraulic fracturing, especially in Brazil.The reason why there are many kinds of test methods for rock tensile testing is that in a long period of time, it is very difficult to realize the direct stretching of rock under the restriction of binder and testing machine, so the majority of scholars adopt other test methods.The difficulty of direct tensile test is circumvented and the tensile strength of rock is obtained indirectly.But at the same time, we also noticed that with the development and progress of rock mechanics test methods, many scholars have successfully carried out direct tensile tests of rocks.After making some reasonable improvements, the direct tensile test of rock can be successfully carried out in this study, and the results are satisfactory.This provides a guarantee for obtaining the most reliable tensile mechanical parameters of rock.But at the same time, it is found that in many cases, because of the limitation of the test instrument, it is not easy to realize the direct tensile test of rock.However, if the direct tensile test and indirect tensile test of rock are compared, the real indexes of rock tensile test in direct tensile test can be compared with the tensile index in indirect tensile test of rock, and the similarities and differences between them can be found.It provides a reference for direct tensile test of rock due to the limitation of test conditions.Four kinds of representative rocks (Quyang granite, marble, Beishan granite, limestone) were selected and covered with three types of rocks, which were made into standard samples to meet the test requirements, and were subjected to uniaxial compression and direct tension respectively.Brazilian splitting and three-point bending tests were performed to obtain the tensile (including direct and indirect) and compressive strength deformation parameters.Based on the analysis of tensile and compression strength and deformation parameters, the reasons for the difference of tensile strength between Brazilian splitting indirect tensile test and direct tensile test are derived through three strength criteria.At the same time, it is found that the deformation parameters (elastic modulus, Poisson's ratio) of rock under these two kinds of forces are very different. According to the test results, the FLAC3D numerical analysis software is used to compare the different properties of rock under tension and compression.The difference between the numerical simulation results and the theoretical results of the Brazilian splitting test method.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU45

【参考文献】