本文選題：黃土節(jié)理 + 剪切強度　； 參考：《西安建筑科技大學(xué)》2017年碩士論文

【摘要】：黃土節(jié)理的剪切強度特性對于含節(jié)理黃土工程的穩(wěn)定性有重要影響,而節(jié)理剪切強度特性與節(jié)理表面形態(tài)密切相關(guān)。為此,需對節(jié)理表面形態(tài)進行了研究。首先,在大量野外調(diào)研的基礎(chǔ)上,選取合適場地采集了天然黃土節(jié)理試樣,利用輪廓曲線儀測量節(jié)理表面形態(tài),并繪制了節(jié)理面輪廓曲線。運用統(tǒng)計學(xué)方法計算了節(jié)理表面特征參數(shù),然后選取高度均方根z1、峰點密度η、坡度均方根z2三個參數(shù),根據(jù)數(shù)據(jù)統(tǒng)計結(jié)果及經(jīng)驗確定單因素分級范圍,利用模糊數(shù)學(xué)方法綜合評價節(jié)理表面形態(tài),最終得到了所取天然黃土節(jié)理試樣表面形態(tài)的綜合特征參數(shù)RJ及分級結(jié)果。依據(jù)節(jié)理表面形態(tài)分級標(biāo)準(zhǔn)制備試樣,采用室內(nèi)小型直剪試驗方法研究了含水量對黃土節(jié)理剪切強度參數(shù)的影響規(guī)律,并對比室內(nèi)大型直剪試驗與小型直剪試驗結(jié)果,研究了尺寸效應(yīng)對剪切強度的影響,根據(jù)所有試驗結(jié)果研究了節(jié)理剪切應(yīng)力-位移關(guān)系曲線特征。節(jié)理表面形態(tài)研究發(fā)現(xiàn)：不同場地間天然黃土土樣的節(jié)理表面形態(tài)存在差異,同一場地,節(jié)理表面形態(tài)相近;各節(jié)理面的峰態(tài)系數(shù)K值的范圍為2~3,均值接近3,表明節(jié)理面的全坐標(biāo)高度分布為高斯分布或準(zhǔn)高斯分布;驗證發(fā)現(xiàn)RJ與節(jié)理剪切強度具有較好的線性相關(guān)性,說明本次對節(jié)理面分級的方法具有可行性。直剪試驗結(jié)果表明：黃土節(jié)理的抗剪強度關(guān)系符合摩爾-庫倫準(zhǔn)則,且粘聚力很小,可以忽略不計;隨含水量的增加,黃土節(jié)理峰值內(nèi)摩擦角最初的變化幅度較小,當(dāng)大于某個含水量值時,峰值內(nèi)摩擦角減小幅度變大,黃土節(jié)理強度隨含水量的變化規(guī)律可用指數(shù)形式進行描述,并提出了節(jié)理剪切強度的經(jīng)驗計算公式,驗證了公式的合理性;黃土節(jié)理直剪試驗存在尺寸效應(yīng),試樣尺寸主要影響節(jié)理面起伏度對剪切強度的貢獻,尺寸越大,其剪切強度也越大;黃土節(jié)理剪切應(yīng)力-位移的關(guān)系曲線屬于無峰值的應(yīng)變硬化型曲線,并提出了合理的本構(gòu)模型;利用提出的本構(gòu)模型擬合試驗結(jié)果,得到了節(jié)理初始剪切剛度,發(fā)現(xiàn)其隨含水量增加減小,隨正應(yīng)力增加呈線性增加。
[Abstract]:The shear strength characteristics of loess joints have an important effect on the stability of loess engineering with joints, and the shear strength characteristics of joints are closely related to the surface morphology of joints. Therefore, it is necessary to study the surface morphology of joints. Firstly, on the basis of a large number of field investigations, natural loess joint samples were collected in a suitable site, the joint surface morphology was measured by profilometer, and the contour curve of joint surface was drawn. The surface characteristic parameters of joints were calculated by statistical method, and then three parameters of high RMS root z1, peak density 畏, slope RMS root z2 were selected, and the single factor classification range was determined according to the statistical results and experience. The surface morphology of joints was evaluated by fuzzy mathematics method, and the synthetic characteristic parameters RJ and classification results of the surface morphology of natural loess joints were obtained. The effect of water content on the shear strength parameters of loess joints was studied by means of laboratory direct shear test, and the results of large-scale direct shear test and small direct shear test were compared. The influence of size effect on shear strength is studied. According to all the experimental results, the characteristics of shear stress-displacement curves of joints are studied. It is found that the joint surface morphology of natural loess soil samples is different between different sites, and the joint surface morphology is similar at the same site. The range of peak coefficient K of each joint plane is 2 ~ 3, the mean value is close to 3, indicating that the whole coordinate height distribution of joint surface is Gao Si distribution or quasi-Gao Si distribution, and it is found that RJ has a good linear correlation with joint shear strength. It shows that the method of joint surface classification is feasible. The results of direct shear test show that the shear strength relationship of loess joints accords with the Moor-Coulomb criterion, and the cohesion is very small, which can be ignored, and the initial variation of the peak internal friction angle of loess joints is small with the increase of water content. When the value of water content is greater than a certain value of water content, the amplitude of peak internal friction angle decreases and the variation of loess joint strength with water content can be described exponentially, and the empirical formula for calculating joint shear strength is put forward. The rationality of the formula is verified: the size effect exists in the direct shear test of loess joints, the size of the specimen mainly affects the contribution of the undulation of the joint surface to the shear strength, and the larger the size, the greater the shear strength; The relationship curve between shear stress and displacement of loess joints is a strain hardening curve without peak value, and a reasonable constitutive model is proposed, and the initial shear stiffness of joints is obtained by fitting the test results with the proposed constitutive model. It is found that it decreases with the increase of water content and increases linearly with the increase of normal stress.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU444

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