本文選題：黃土崩塌 + 切坡��； 參考：《西安科技大學》2015年碩士論文

【摘要】：黃土崩塌作為黃土地區(qū)地質(zhì)災害的一種形式,其危害性極大。大量實踐表明,人為地對邊坡進行切坡卸荷是導致黃土崩塌的主要原因之一。隨著經(jīng)濟的發(fā)展,居民的增加和城市的不斷擴大,為了擴大建筑用地,切坡施工將大大增加,潛在的崩塌災害也將隨之增加。針對研究切坡卸荷引起黃土崩塌的機理及切坡卸荷實踐工程的需要,以切坡卸荷誘發(fā)黃土土體節(jié)理裂隙擴展機理為研究主旨做了較全面的研究。首先對洛川塬邊Q3原狀黃土的基本物理力學性質(zhì)進行分析;然后利用GDS非飽和土三軸儀模擬不同卸荷條件下黃土土體的卸荷應(yīng)力路徑,并借助CT掃描儀、電鏡掃描儀觀察卸荷前后土樣內(nèi)部細觀、微觀結(jié)構(gòu)的變化,探討黃土體節(jié)理裂隙擴展的影響因素及擴展機理;最后結(jié)合FLAC3D對垂直裂隙擴展過程的數(shù)值模結(jié)果,總結(jié)切坡卸荷作用下節(jié)理裂隙擴展機理,為切坡卸荷實踐工程提出指導性意見。通過對以上試驗結(jié)果分析,得到以下結(jié)論:(1)卸荷應(yīng)力路徑下黃土體的強度要比常規(guī)三軸壓縮強度小得多,且應(yīng)力-應(yīng)變曲線隨著含水率、初始卸荷圍壓的增大逐漸由軟化型過渡到硬化型,卸荷的過程中土樣出現(xiàn)剪脹。(2)不同卸荷條件下土樣的變形破壞特征不同,總體上可為劈裂破壞、滑移破壞和塑性破壞三種破壞模式。(3)卸荷后土樣斷面不同區(qū)域的CT數(shù)大部分出現(xiàn)增大的趨勢,卸荷量、卸荷速率、含水率、初始圍壓越大,CT數(shù)增幅越大;中心的方差大部分減小,大區(qū)和全區(qū)的方差值大部分增大。(4)卸荷條件對黃土節(jié)理裂隙的擴展具有一定程度的影響,只有達到一定的卸荷量時土樣才會出現(xiàn)裂隙,卸荷速率較小、含水率較大、初始卸荷圍壓較大時,土樣容易出現(xiàn)粗大的裂隙,反之,微裂隙較發(fā)育。(5)卸荷裂隙的產(chǎn)生是內(nèi)外因素共同作用的結(jié)果,內(nèi)部因素有顆粒集配、礦物質(zhì)含量、結(jié)構(gòu)特征等,外部因素主要是切坡卸荷和水。
[Abstract]:As a form of geological disaster in loess area, loess collapse is very harmful. A great deal of practice shows that cutting slope unloading is one of the main causes of loess collapse. With the development of economy, the increase of residents and the expansion of cities, in order to expand the construction land, slope cutting construction will be greatly increased, and the potential collapse disaster will also increase. In order to study the mechanism of loess collapse caused by sloping unloading and the need of practical engineering of sloping unloading, the mechanism of fracture expansion of loess soil induced by sloping unloading is studied comprehensively. The basic physical and mechanical properties of Q3 undisturbed loess in Luochuan tableland are analyzed firstly, then the unloading stress path of loess soil under different unloading conditions is simulated by GDS unsaturated soil triaxial instrument, and the unloading stress path of loess soil is simulated by CT scanner. The microstructure of soil samples before and after unloading was observed by electron microscope scanner, and the influencing factors and mechanism of fracture propagation of loess body were discussed. Finally, the numerical model results of FLAC3D for vertical fracture propagation were combined. The mechanism of joint crack expansion under the action of sloping unloading is summarized, and some guiding suggestions are put forward for the practical engineering of sloping unloading. Through the analysis of the above test results, the following conclusion is drawn: the strength of loess body under unloading stress path is much smaller than that of conventional triaxial compression, and the stress-strain curve is with moisture content. The increase of initial unloading confining pressure gradually changes from softening type to hardening type. During unloading, the soil sample appears shear dilatation. (2) the deformation and failure characteristics of the soil sample under different unloading conditions are different, which can be divided into fracturing failure, as a whole, the deformation and failure characteristics of the soil sample under different unloading conditions are different. After unloading, the CT number of different areas of soil sample section showed an increasing trend. The larger the unloading amount, unloading rate, water content and initial confining pressure, the larger the increase of CT number. The variance of the center is mostly reduced, and the square difference between the large area and the whole area is mostly increased. The unloading condition has a certain degree of influence on the expansion of the loess joint fracture. Only when the unloading amount reaches a certain amount, the soil sample will appear a crack, and the unloading rate will be smaller. When the water content is high and the initial unloading confining pressure is high, the coarse cracks are easy to appear in the soil samples, whereas, the micro-cracks are relatively developed. The generation of unloading fractures is the result of the interaction of internal and external factors, and the internal factors include particle aggregate, mineral content, and so on. Structural characteristics, external factors are mainly cut slope unloading and water.
【學位授予單位】：西安科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU444

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