黄土各向异性及抗拉本构关系在隧道工程中的应用

发布时间：2018-05-15 11:06

本文选题：黄土 + 各向异性　；参考：《兰州交通大学》2015年硕士论文

【摘要】：通过室内应变控制式三轴仪,测定兰州榆中县王家沟隧道水平方向与竖直方向上的抗剪强度各向异性,用轴向压裂的方法测定水平与竖直方向上抗拉强度各向异性,测定兰州九州重塑黄土在不同干密度不同含水量下的抗剪、抗拉强度,测定王家沟隧道与定西北二十里铺隧道重塑黄土抗剪、抗拉强度。详细对比分析黄土抗剪各向异性以及抗拉强度各向异性,含水量、干密度、粘聚力、内摩擦角、孔隙比、饱和度等对黄土抗拉强度的影响,通过TanleCuver3D三维数据处理软件,讨论含水量与干密度、粘聚力与内摩擦角、孔隙比与饱和度等双重因素共同作用下对黄土抗拉强度的影响,通过对轴向压裂法测定土体抗拉强度及试样破坏模式进行力学机理分析,讨论传统轴向压力法计算黄土抗拉强度公式的适用性,针对黄土遇水结构性减弱的特点,分析黄土隧道开挖过程中易发生塌方事故的作用机理,探讨黄土抗拉强度在隧道塌方事故中的应用。结果表明:竖直方向上的无侧限抗压强度、抗拉强度以及抗剪强度均高于水平方向上,且提出黄土各向异性强度简化几何模型。黄土竖直最大偏差应力与水平向最大偏差应力比在低围压下较大,达到1.35左右,高围压下比值较小,仅有1.03左右,说明黄土各向异性在低围压下受影响较大,且低围压时黄土偏差应力与应变关系表现为应变软化,高围压时表现为应变硬化规律,且水平向的塑性比竖直向的强。对传统E-P模型进行修正,将黄土试样剪切破坏过程分为线弹性阶段、弹塑性应力峰值阶段和塑性破坏阶段,得出适合于有峰值出现的应变软化的模型,由试验结果按照硬化规律可将黄土分为强硬化、硬化、弱硬化、弱软化、软化、强软化六类。黄土抗拉强度随含水量的增大而减小,且成二次多项式形式,随干密度的增大而增大,拉应力达到抗拉强度时的轴向贯入深度在相同干密度条件下随含水量的增大先减小后增大,在相同含水量条件下随干密度增大先增大后减小。无侧限抗压强度与抗拉强度呈线性关系,且相关性较好,拉压强度比的最大值出现在最优含水量和最大干密度附近,最小值则出现在干密度最小处,含水量最大处。粘聚力与内摩擦角正切值的乘积分别于抗拉强度与无侧限抗压强度呈幂指数关系。抗拉和无侧限抗压强度均随空隙比、饱和度的增大而减小,饱和度和孔隙比分别对抗拉和无侧限抗压强度呈二次多项式关系。将抗拉几何模型简化为三类,第一,高干密度低含水量;第二,含水量和干密度居中;第三,低干密度高含水量。综合影响因素对抗拉强度的结果表明:黄土抗拉强度受含水量、干密度双重因素影响,含水量对抗拉强度的影响程度高于干密度,受饱和度与空隙比双重因素影响,且饱和度对抗拉强度的影响高于空隙比,粘聚力和内摩擦角方面,抗拉强度受粘聚力影响较大,受内摩擦角影响较小。通过对抗拉强度力学特性分析可知,抗拉强度与粘聚力及无侧限抗压强度之间存在线性关系,由试验结果验证可知,无侧限抗压强度与抗拉强度之比接近13.8,抗拉强度与粘聚力之比接近0.22。隧道塌方分为浅埋整体塌方和深埋局部塌方,前者满足摩尔-库伦理论或广义摩尔-库伦理论,即塌方由抗剪强度不足引起,后者满足最大伸长拉伸线应变理论,即塌方由抗拉强度不足引起。
[Abstract]:The shear strength anisotropy in horizontal direction and vertical direction of Wangjia Gou tunnel, Yuzhong County, Lanzhou, is measured by three axis strain control instrument, and the anisotropy of tensile strength in horizontal and vertical direction is measured by axial fracturing, and the shear strength and tensile strength of Lanzhou Jiuzhou remolded loess under different dry density and different water content are measured. The shear resistance and tensile strength of the Wangjia tunnel and the northwest twenty Li Pu tunnel are determined. The influence of the shear anisotropy and the anisotropy of the tensile strength, water content, dry density, cohesive force, internal friction angle, pore ratio, saturation and so on on the tensile strength of loess are analyzed in detail, and the TanleCuver3D 3D data processing software is used to discuss the effect of the Loess The effects of water content and dry density, cohesive force and internal friction angle, pore ratio and saturation on tensile strength of loess are discussed. The mechanical mechanism of tensile strength of soil and failure mode of specimen is analyzed by axial fracturing method, and the applicability of traditional axial compression method to calculate the tensile strength formula of Loess is discussed. According to the characteristics of the structural weakening of the loess, the mechanism of the collapse accident in the excavation of the loess tunnel is analyzed, and the application of the tensile strength of the Loess in the tunnel collapse is discussed. The results show that the unconfined compressive strength in the vertical direction, the tensile strength and the shear strength are all higher than the horizontal direction, and the Loess anisotropy is put forward. The maximum deviations stress ratio of loess vertical maximum deviation stress and horizontal maximum deviation stress ratio under low confining pressure is larger, about 1.35, the ratio of high confining pressure is smaller, only about 1.03, indicating that the anisotropy of loess is greatly influenced by low confining pressure, and the relationship between stress and strain of loess is strain softening under low confining pressure. The high confining pressure is characterized by strain hardening law, and the horizontal plasticity is stronger than the vertical direction. The traditional E-P model is modified. The shear failure process of the Loess specimen is divided into linear elastic stage, the peak stage of elastoplastic stress and the stage of plastic failure, and the strain softening model suitable for peak occurrence is obtained, and the test results are in accordance with the hardened test results. The law can divide loess into six kinds: strong hardening, hardening, weak hardening, weak softening, softening, and strong softening. The tensile strength of loess decreases with the increase of water content, and becomes two polynomial form, which increases with the increase of dry density. The axial penetration depth of tensile stress reaches the same dry density and decreases with the increase of water content in the same dry density condition. In the same water content, it increases first and then decreases with the increase of dry density under the same water content. The unconfined compression strength is linear with the tensile strength, and the correlation is good. The maximum value of the tensile compression strength ratio appears near the optimal water content and the maximum dry density. The minimum value appears at the minimum dry density and the maximum water content. Cohesion and internal strength. The product of the tangent value of the friction angle has a power exponent relationship with the tensile strength and the unconfined compression strength respectively. The tensile and unconfined compressive strength decreases with the increase of the void ratio, the saturation and the void ratio, respectively. The tensile geometric model is simplified to the three class, the first and the high. Dry density is low water content, second, water content and dry density are middle, third, low dry density and high water content. The results of comprehensive influence factors on tensile strength show that the tensile strength of loess is influenced by water content and dry density, and the influence of water content on tensile strength is higher than that of dry density, and it is influenced by double factors of saturation and void ratio, and The influence of saturation on the tensile strength is higher than the void ratio, the cohesion and the internal friction angle, the tensile strength is greatly influenced by the cohesive force and less influenced by the internal friction angle. Through the analysis of the mechanical characteristics of the tensile strength, it is known that there is a linear relationship between the tensile strength and the cohesive force and the unconfined compression strength. The ratio of compressive strength to tensile strength is close to 13.8, and the ratio of tensile strength to cohesive force is close to 0.22. tunnel collapse divided into shallow buried whole collapse and deep buried local collapse. The former satisfies the Moore Kulun theory or the generalized Moore Kulun theory, that is, the collapse is caused by the lack of shear strength, and the latter satisfies the maximum elongation tension line strain theory, that is, the landslide. It is caused by the lack of tensile strength.

【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U452.11

【参考文献】