【摘要】：在荷載作用下,巖石不僅表現(xiàn)出彈性和塑性,而且具有與時間相關(guān)的性質(zhì),即巖石的流變性。工程實踐中,巖石流變現(xiàn)象隨處可見,巖石流變所造成的危害也不容忽視。如隧道、礦山洞室掘進后,圍巖隨時間產(chǎn)生變形甚至破壞;地基在附加荷載作用下隨時間逐漸沉降,最終導(dǎo)致建筑物變形破壞。多年來,巖石流變特性研究取得了豐富的成果。但巖石作為一種特殊的工程材料,其流變特性受到包括巖石本身性質(zhì)(如礦物組成、節(jié)理等)和外部環(huán)境(濕度、地應(yīng)力等)等諸多方面的綜合影響,以致目前為止巖石流變理論仍不甚完善。為了預(yù)測復(fù)雜應(yīng)力環(huán)境中巖石工程長期穩(wěn)定性,本文采用YSJ-01-00巖石三軸壓縮流變試驗儀和YZJL-300巖石直剪流變儀對完整砂巖和預(yù)制裂隙砂巖開展三軸壓縮和剪切蠕變試驗,基于試驗結(jié)果并結(jié)合理論分析和數(shù)值計算,研究了巖性、圍壓、軸壓、含水率、裂隙長度等因素與砂巖蠕變特性的關(guān)系。具體研究內(nèi)容及結(jié)論如下:(1)通過常規(guī)單軸壓縮試驗和三軸壓縮試驗,測得細砂巖和粗砂巖抗壓強度、內(nèi)聚力和內(nèi)摩擦角。(2)通過三軸壓縮蠕變試驗,獲得細砂巖和粗砂巖在三向應(yīng)力作用下的蠕變規(guī)律。隨軸壓增加,細砂巖表現(xiàn)出減速和等速兩階段蠕變過程,粗砂巖則表現(xiàn)出減速、等速和加速三階段蠕變過程。由于時效性,巖石長期抗壓強度降低。細砂巖長期強度參數(shù)內(nèi)聚力隨時間降低,而內(nèi)摩擦角基本無變化;粗砂巖內(nèi)聚力和內(nèi)摩擦角同時隨時間減小。通過不同含水率粗砂巖三軸壓縮蠕變試驗,發(fā)現(xiàn)巖石含水率越高,瞬時應(yīng)變越大、蠕變速率越高、長期強度越低,瞬時應(yīng)變與含水率呈線性關(guān)系,長期強度與含水率呈對數(shù)關(guān)系。(3)通過剪切蠕變試驗獲得完整砂巖和預(yù)制裂隙砂巖蠕變規(guī)律。結(jié)果表明,正應(yīng)力增加,巖石抗剪長期強度增加,剪切破裂面越光滑且接近預(yù)制裂隙平面;剪應(yīng)力增加,巖石表現(xiàn)出減速蠕變、等速蠕變和加速蠕變?nèi)齻�過程;裂隙長度增加,巖石長期抗剪強度快速降低,瞬時剪切應(yīng)變增加。(4)采用Cvisc模型對砂巖三軸壓縮蠕變和剪切蠕變?nèi)糖�進行了成功辨識,得到Cvisc模型參數(shù)。在數(shù)值計算中調(diào)用Cvisc模型對砂巖三軸壓縮蠕變規(guī)律進行模擬,數(shù)值結(jié)果與試驗數(shù)據(jù)較吻合,驗證了該模型對于描述砂巖蠕變性質(zhì)的適用性。將研究成果應(yīng)用于砂巖地基在建筑物附加應(yīng)力下蠕變沉降分析,在應(yīng)力較低時,地基蠕變速率小,且快速降低至零;在較高應(yīng)力情況下,地基蠕變速率先降低,隨后保持不變,地基變形隨時間逐漸增加。該研究可為工程實踐提供參考。
[Abstract]:Under loading, rock not only shows elasticity and plasticity, but also has the property of time-dependent, that is, the rheology of rock. In engineering practice, the phenomenon of rock rheology can be seen everywhere, and the harm caused by rock rheology can not be ignored. For example, after excavation of the tunnel, the surrounding rock will deform or even destroy with time, and the foundation will gradually subside with time under the action of additional load, which will eventually lead to the deformation and failure of the building. Over the years, a wealth of achievements have been made in the study of rock rheology characteristics. However, as a special engineering material, the rheological properties of rock are influenced by many aspects, such as the properties of rock itself (such as mineral composition, joint, etc.) and the external environment (humidity, in-situ stress, etc.). So far, the theory of rock rheology is still not perfect. In order to predict the long-term stability of rock engineering in complex stress environment, In this paper, YSJ-01-00 rock triaxial compression rheometer and YZJL-300 rock direct shear rheometer are used to carry out triaxial compression and shear creep tests on intact sandstone and prefabricated fractured sandstone. Based on the test results, combined with theoretical analysis and numerical calculation, The relationship among lithology, confining pressure, axial compression, moisture content, fracture length and creep characteristics of sandstone is studied. The concrete research contents and conclusions are as follows: (1) the compressive strength, cohesion and internal friction angle of fine sandstone and coarse sandstone are measured by conventional uniaxial compression test and triaxial compression test. (2) through triaxial compression creep test, the compressive strength, cohesion and internal friction angle of fine sandstone and coarse sandstone are measured. The creep law of fine sandstone and coarse sandstone under three-dimensional stress is obtained. With the increase of axial pressure, the fine sandstone exhibits two-stage creep process of deceleration and constant velocity, while the coarse sandstone shows deceleration, constant velocity and accelerated three-stage creep process. Due to time-effectiveness, the long-term compressive strength of rock decreases. The cohesion of the long-term strength parameter of fine sandstone decreases with time, but the angle of internal friction basically does not change, while the cohesion and angle of internal friction of coarse sandstone decrease with time at the same time. Through triaxial compression creep tests of coarse sandstone with different moisture content, it is found that the higher the water content of rock is, the greater the instantaneous strain is, the higher the creep rate is, the lower the long-term strength is, and the linear relationship between instantaneous strain and moisture content. There is a logarithmic relationship between long-term strength and water content. (3) the creep law of intact sandstone and prefabricated fractured sandstone is obtained by shear creep test. The results show that with the increase of normal stress, the shear strength of rock increases and the shear fracture surface becomes smoother and closer to the prefabricated crack plane, and the rock exhibits three processes: deceleration creep, constant velocity creep and accelerated creep when the shear stress increases. With the increase of fracture length, the long-term shear strength of rock decreases rapidly and the instantaneous shear strain increases. (4) the triaxial compression creep and shear creep curves of sandstone are identified successfully by using Cvisc model, and the parameters of Cvisc model are obtained. In the numerical calculation, the Cvisc model is used to simulate the triaxial compression creep law of sandstone. The numerical results are in good agreement with the experimental data, and the applicability of the model to describe the creep properties of sandstone is verified. The research results are applied to the creep settlement analysis of sandstone foundation under the additional stress of the building. When the stress is low, the creep rate of the foundation is small and the creep rate is reduced to zero rapidly. Under the condition of high stress, the creep velocity of the foundation decreases at first, then remains unchanged, and the deformation of the foundation increases gradually with the time. This study can provide reference for engineering practice.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU45

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