湘南红层滑带土直剪蠕变特性及长期强度试验研究

发布时间：2018-04-20 19:19

本文选题：红层滑带土 + 蠕变　；参考：《南华大学》2014年硕士论文

【摘要】：大量边坡工程表明：边坡失稳部分由滑动带的剪切蠕变破坏造成，因而研究其滑动带的剪切蠕变特性和其长期强度尤为重要。红层呈软硬互层的特点，软弱夹层是其滑带土形成的物质基础，当软弱夹层的含水量变化时对边坡稳定性影响非常明显。湘南红层边坡常因为人工开挖及排、防水处理不当，导致失衡形成滑坡。对滑带土的流变特性及长期强度已有许多科研工作者做了大量的研究工作，但专门针对湘南红层滑带土剪切蠕变特性的研究报告尚不多见。本文通过对湘南某红层滑坡滑带土直剪蠕变试验，研究该滑带土在不同垂直荷载、含水率条件下，分级施加水平剪力之后的蠕变特性，得出其剪切位移—时间关系曲线及剪切位移—剪应力曲线，为确定滑带土长期强度及计算边坡变形提供依据，主要取得了以下进展。 (1)本文通过对湘南红层滑带土进行了室内直剪蠕变试验，初步探讨了该土在不同垂直荷载、含水率下的蠕变特性。试验结果表明：由于红层滑带岩层破碎，水沿红层裂隙下渗至滑动带，使其软化，加速了其剪切蠕变的发展；当剪切应力达到滑带土长期极限抗剪强度时，当含水率一定，若垂直荷载较小，滑带土则表现为突然剪破；当垂直荷载足够大，滑带土则以稳定的加速蠕变发展；当含水率和垂直荷载一定时，随着剪切应力的增大，土体的剪切位移逐渐增大，整个蠕变阶段逐渐呈现；衰减蠕变，等速蠕变、加速蠕变三个蠕变阶段。在剪切应力、垂直荷载一定的条件下，，含水率越大，滑带土的非线性流变特征越明显，产生的总剪切位移也越大。 (2)通过对直剪蠕变试验结果中红层滑带土的剪应力—剪切位移等时曲线的研究分析，得出其变化规律及特性，以此提出了流变模型中红层滑带土的两个流变参数，蠕变变形速率和剪切模量。经试验发现：红层滑带土的剪应力—剪切位移等时曲线呈明显的非线性流变特点，表现为：随着剪应力和时间的持续增加，曲线将逐渐朝应变轴靠拢；在同一含水率情况下，红层滑带土的剪切模量的变化与时间及剪切水平的变化呈反比特点。 (4)将长期强度理论与土体在蠕变试验中的破坏准则相结合，建立了湘南红层滑带土的幂函数形式的长期强度方程。该方程较好的描述了土体在长期荷载作用下所经历的三个蠕变状态，完成了对湘南红层滑带土长期强度特征的模拟，为红层滑带边坡的变形问题、强度问题和稳定性问题的分析提供了理论依据。
[Abstract]:A large number of slope projects show that the failure of slope stability is caused by the shear creep failure of the slip zone, so it is very important to study the shear creep characteristics and long-term strength of the slip zone. The red layer is soft and hard interbedded, and the weak intercalation is the material foundation of the soil in the slip zone. When the water content of the weak intercalation changes, the slope stability is obviously affected. The red bed slope in southern Hunan is often caused by artificial excavation and drainage and improper waterproof treatment, which leads to the imbalance of landslide. Many researchers have done a lot of research on the rheological characteristics and long-term strength of sliding zone soils, but there are few reports on the shear creep characteristics of red bed soils in southern Hunan. In this paper, the creep characteristics of a red layer landslide sliding zone soil under different vertical loads and moisture content are studied by means of direct shear creep test. The shear displacement-time relation curve and shear displacement-shear stress curve are obtained, which provide the basis for determining the long-term strength of sliding zone soil and calculating the slope deformation. In this paper, the creep characteristics of the red layer sliding zone soil under different vertical loads and moisture content are preliminarily discussed by means of indoor direct shear creep test. The test results show that due to the breakage of the rock layer in the red layer slip zone, water seeps down along the red bed fissure to the slip zone, which softens it and accelerates the development of its shear creep, and when the shear stress reaches the ultimate shear strength of the sliding zone soil for a long time, the moisture content is constant. If the vertical load is small, the slip zone soil appears to be suddenly shearing; when the vertical load is large enough, the sliding zone soil develops steadily and accelerates creep; when the moisture content and vertical load are constant, the shear stress increases with the increase of shear stress. The shear displacement of the soil gradually increases and the whole creep stage gradually appears; the decay creep, the constant velocity creep and the accelerated creep are three creep stages. Under the condition of shear stress and vertical load, the higher the moisture content is, the more obvious the nonlinear rheological characteristics of sliding zone soil are, and the larger the total shear displacement is. 2) through the study and analysis of shear stress-shear displacement isochron curve of red layer sliding zone soil in direct shear creep test results, the variation law and characteristic are obtained, and two rheological parameters of red layer slip zone soil in rheological model are put forward. Creep deformation rate and shear modulus. The experimental results show that the shear stress-shear displacement isochron curve of red layer slip zone soil shows obvious nonlinear rheological characteristics, which shows that with the increasing of shear stress and time, the curve will gradually close to the strain axis, and under the same water content, The variation of shear modulus of red layer slip zone soil is inversely proportional to time and shear level. 4) combining the long-term strength theory with the failure criterion of soil in creep test, the long-term strength equation of the soil in the form of power function of the red layer slip zone in southern Hunan is established. The equation well describes the three creep states experienced by soil under long-term load, and completes the simulation of the long-term strength characteristics of the red bed slip zone soil in southern Hunan Province, which is the deformation problem of the red bed slip zone slope. The analysis of strength problem and stability problem provides theoretical basis.
【学位授予单位】：南华大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU411

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