【作者】 李红；

【导师】 彭建兵；

【作者基本信息】 长安大学 ， 地质工程， 2010， 硕士

【摘要】 目前,地裂缝的发育分布特征和活动特点等已经被人们基本掌握,但在成因机理方面的研究还不够成熟,仍存在不同观点和争议,另外已有裂缝再次开裂扩展的机理尚需深入研究。本文以汾渭盆地地裂缝为研究背景,以西安市f14地裂缝探槽和泾阳地震台地裂缝探槽为试验场地,通过对地裂缝发育的介质环境—黄土(包括原状黄土、裂隙性黄土、重塑黄土)进行三轴拉伸特性试验研究,分析了与地裂缝有关的黄土破裂特性及破裂行为,并在此基础上讨论了黄土地区地裂缝的成因机制与扩展机理。原状黄土的三轴拉伸试验表明,黄土的抗拉强度及极限拉应变均很小,且随着围压的增大,其断裂时的轴向应力由拉应力向压应力转变。当黄土体内应力储备大于其极限强度时,内部应力便会寻找一种可以释放能量的通道,很容易在地表土体中产生拉张裂缝,且随着深度的增加,逐渐呈闭合的趋势。裂隙性黄土的三轴拉伸破裂特性试验表明,其破裂主要受控于所处的应力状态及土体中原有的宏观结构面,在低围压情况下,裂隙性黄土更容易沿原有裂隙结构面产生裂缝而破坏,黄土体中多数地裂缝是在土体中原有的结构面上发育起来的。重塑黄土的三轴拉伸试验表明,土体的抗拉强度与围压和含水率关系密切。单轴拉伸情况下,抗拉强度随着含水率的增大呈先增大后减小的趋势,三轴拉伸情况下,抗拉强度随着含水率的增大而减小。与此同时,笔者从微观角度对重塑土单轴抗拉强度进行了理论预测,含水量为10%时预测值为7.4kPa,实测值为7.9kPa；含水量为15%时,预测值为10.25kPa,实测值为12.1kPa,预测值与试验结果吻合较好。黄土在各种作用下的破裂特性试验研究表明,汾渭盆地的构造应力场是引发地裂缝的主控因素,其他一些作用则为附加因素。更多还原

【Abstract】 Recently, the distribution and activity character of ground fissure have been mastered basically, but its genetic mechanism is immature being many different points of view and disputes on it because there are some key basic problems being unresolved. This paper researched the mechanism of ground fissures in Fen-Wei basin by experiment studying loess samples with fracture fillings and without fracture fillings excavated from the trench in Xi’an and Jing-yang ground fissures field. Based on a series of triaxial tensile test of loess, the rupture characteristics and behavior related to loess ground fissures were analyzed and the genesis and expansion mechanism of ground fissures developed in loess were discussed.The triaxial tensile test of intact loess indicates that the tensile strength and strain of loess are very small. And with the increase of confining pressure, the tensile stress would become compressive stress. When the tensile stress in loess is bigger than tensile strength, the tensile cracks would come into being to release the tensile stress, with the buried depth increases, the crack would become closed. The triaxial tensile test of loess with fracture fillings indicates that the stress state and the initial structural plane controlled the rupture development and cracks are easier to be formed near initial cracks under low confining pressure. The triaxial tensile test of remolded loess indicates that the tensile strength of loess is related to the confining pressure and water content. Under uniaxial tension, with increasing of water content, the tensile strength increases firstly and then decreases, Under triaxial tension, with increasing of water content, tensile strength decreases At the same time, the author carried out theoretical analysis from microscopic view to predict the uniaxial tensile strength of remolded loess. The predicted value is 7.4kPa and the measured value is 7.9kPa when w=10%; The predicted value is 10.25kPa and the measured value is 12.1kPa when w=15%;which indicates theoretical analysis agree with the test result well。The broken test of loess showed that the tectonic stress field of Fen-Wei basin was the controlling factor to ground fissures, and other factors were additional factors.更多还原