本文選題：抗拉　切入點：抗壓　出處：《南京大學》2014年碩士論文

【摘要】：由于巖石屬于典型的脆性材料,其能夠承受的抗拉強度遠小于抗壓強度,這使對于巖石抗拉性能的研究變得很重要。要研究巖石在拉伸狀態(tài)下的各種屬性,首先要獲得巖石在拉伸狀態(tài)下的各種力學參數(shù),主要包括抗拉強度、彈性模量和泊松比等。要獲得巖石拉伸狀態(tài)下的力學參數(shù)最直接的方法便是通過巖石力學室內(nèi)試驗進行測量。 通過對現(xiàn)有文獻資料的查閱,不難發(fā)現(xiàn),巖石的拉伸試驗不像巖石壓縮試驗只有單軸壓縮試驗一種那么單一,而是存在著直接拉伸、巴西劈裂、三點彎曲、圓環(huán)破裂和水壓致裂等多種試驗方式,而且尤以巴西劈裂試驗用的最為廣泛。產(chǎn)生巖石拉伸試驗多種試驗方法林立現(xiàn)狀的原因無非是在相當長的一段時間內(nèi),受粘結劑和試驗機的限制實現(xiàn)巖石的直接拉伸相當困難,所以廣大學者通過其他試驗方法,繞開了直接拉伸試驗實現(xiàn)的難點,間接求取了巖石的抗拉強度。但同時我們也注意到,隨著巖石力學試驗方法的發(fā)展和進步,已經(jīng)有很多學者成功的進行了巖石的直接拉伸試驗,通過對他們試驗方法的研究,結合現(xiàn)有試驗儀器,做出一些合理的改進后,本研究中同樣能夠成功的進行巖石的直接拉伸試驗,且試驗結果令人滿意。這便為獲得最可靠的巖石拉伸力學參數(shù)提供了保證。但同時發(fā)現(xiàn)很多情況下因為試驗儀器的限制,實現(xiàn)巖石的直接拉伸試驗尚不易,但若對巖石直接拉伸試驗和間接拉伸試驗做出對比研究則可以以直接拉伸試驗中真實的巖石拉伸試驗指標對比巖石間接拉伸試驗中的拉伸指標,從而發(fā)現(xiàn)兩者的異同,為因試驗條件限制而無法進行巖石直接拉伸試驗的情況做參考。 選擇了4種比較有代表性的巖石(曲陽花崗巖、大理巖、北山花崗巖、灰?guī)r)含蓋了3大巖類,分別制成滿足試驗需求的標準試樣,分別進行了單軸壓縮、直接拉伸、巴西劈裂和三點彎曲試驗,得到其在拉伸(包括直接拉伸和間接拉伸)和壓縮下的強度變形參數(shù)。 通過對拉伸和壓縮強度和變形參數(shù)的分析,首先通過三大強度準則,推導了巴西劈裂間接拉伸試驗抗拉強度和直接拉伸試驗抗拉強度差異性的原因。同時發(fā)現(xiàn)巖石在這兩種受力情況下的變形參數(shù)(彈性模量、泊松比)差異非常大,對此根據(jù)試驗結果采用FLAC3D數(shù)值分析軟件,比較了在考慮拉伸和壓縮下巖石不同性質(zhì)的前提下,巴西劈裂試驗方法數(shù)值模擬結果和理論計算結果的差異。
[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.
【學位授予單位】：南京大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU45

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本文編號：1713213