【作者】 孙萍；

【导师】 彭建兵；

【作者基本信息】 长安大学 ， 地质工程， 2007， 博士

【摘要】 岩土体在外力作用下会发生各种各样的破坏,包括拉裂破坏、剪切破坏及塑性流变软化等。发育于汾渭盆地黄土体中的地裂缝,其成因复杂多样,实质上也是土体在应力—渗流—损伤耦合作用下的一种破裂行为。本文以汾渭盆地地裂缝为研究背景,以三原县双槐树村地裂缝试验场为试验场地,通过对地裂缝发育的介质环境—黄土(包括裂隙性黄土)进行抗拉、抗剪、流变特性力学试验研究,以及各种作用下的数值试验研究,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。黄土的单轴拉伸试验表明,黄土的抗拉强度与极限拉应变值均很小,地质环境下发育的黄土地裂缝与黄土的弱抗拉特性有着密切的关系,当黄土体内拉应力储备大于其抗拉强度时,拉应力便会寻找一种可以释放能量的通道,于是在土中产生拉张裂缝;黄土的蠕变试验表明,土体达到破坏性蠕变阶段时的极限应变与围压及含水率大小有关,高湿度黄土具有更明显的流变软化特性,三原地表张开的地裂缝与突降暴雨的短期浸泡作用直接相关,属于浸润作用下的短期流变软化—开裂问题,深部地裂缝则存在长期应力作用下的蠕变现象;裂隙性黄土的抗拉破裂及抗剪破裂特性表明,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;借助数值分析软件RFPA,真实地再现了土体中裂纹的萌生、扩展至贯通过程,并且确定出了各种因素作用下的起裂应力及裂纹扩展路径。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】 The soil would generate all sorts of broken under the function of external force, such as the tensile broken, the shear broken and the plastic rheology. The ground fissure developed in Fen-Wei basin had the complex genesis, and was a kind of soil broken under the coupling function of stress, seepage flow and impairment. The author in this paper researched the mechanism of ground fissures in Fen-Wei basin according to the ground fissures in Sanyuan testing field. Based on a series of mechanical test of loess, such as tensile test, shear test, creep test and numerical test, analyzed the rupture characteristics and behavior related to loess ground fissures. Based on this, discussed the genesis and expansion mechanism of ground fissures developed in loess.The tensile test indicated that the ground fissures developed in loess were concerned to the very small tensile strength and limit strain of loess. When the tensile stress in loess was bigger than tensile strength, the tensile cracks would come into being to release the tensile stress. The creep test indicated that the limit strain in destructive creep stage was related to the confining pressure and water content, and the high water content loess had the more obvious rheological softening character. The Sanyuan ground fissure developed on the ground surface was nearly connected with dump rainstorm, and ground fissure developed in deep layer was related to creep under the function of long-term stress. The test of fissured loess indicated that, the stress state and the original structural plane controlled the rupture of fissures loess, and the fissured loess was easier to produce cracks under low confining pressure. By using the numerical analyzing software RFPA, the initiation, the expansion and the penetrating of fissures in loess were reappeared, and the stress and expansion path of cracks were determined.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