饱和度对粉土灵敏度影响的室内试验研究

发布时间：2018-03-11 11:05

本文选题：土的结构性　切入点：灵敏度　出处：《太原理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：土的结构性是决定土体力学特性的一个极为重要的内在因素。本文通过室内无侧限抗压强度试验与锥入度试验分别对粉土的灵敏度和锥入度之比进行了研究，并且从这两个方面来分析土体受到扰动和饱和度变化时土体结构性的变化规律。试验结果表明：（1）当粉土受到浸水的影响时从灵敏度随饱和度的变化规律可知，土体饱和度在70%左右土对外荷载的反应最灵敏，此时灵敏度取得最大值，而且土体扰动前后强度变化明显，在受到外界荷载的作用下土体容易发生破坏。（2）在应变灵敏度的试验结果分析中，通过试验可知应变灵敏度随应变曲线变化的峰值点代表着原状土有裂缝出现的时刻。峰值点以前土体的变形为塑性变形，峰值点以后土体逐渐失去原有的结构,伴随着裂缝的不断开展，原状土与重塑土之间抗压能力的差距越来越小，相应的应力的比值逐渐减小曲线下降。（3）在应力灵敏度的试验结果分析中应力灵敏度随应变变化曲线图没有出现峰值点，曲线呈单调上升的趋势，并且随着压力的增加原状土的变形速率大于重塑土的变形速率。因此，同一应力状态下应力灵敏度比值也越来越大，曲线图也客观地反映了加荷对土体结构的影响。（4）从三种灵敏度的比较分析可知，应变灵敏度侧重于土的结构强度，比值越大说明原状土与重塑土的强度差越大，因此土扰动前后受到外荷载作用时土体的反应越灵敏。应力灵敏度则侧重于土的变形能力，比值越大说明随着力在相同微小增量的情况下原状土变形的变化增速要比重塑土变形的变化增速大。通常定义的灵敏度只是单一的通过土体破坏后原状土与重塑土的强度比来反映土灵敏度的强弱。（5）在锥入度之比的数值分析中，锥入度的比值随着饱和度由低到高的变化，其比值先呈现出下降的趋势，大概在饱和度达到70%左右比值达到最小值，然后随着饱和的度的增加曲线呈现出上升的趋势，，而且不论饱和度如何变化锥入度的比值都小于1。（6）锥入度之比与三种灵敏度的比较分析表明，锥入度之比与通常定义的灵敏度，二者在表现土体结构性时有着对应的关系，曲线图近似为轴对称图形，并且灵敏度越大土体的结构强度越明显，相反锥入度之比越小土的结构强度也越明显；从整体上来说锥入度之比与应变灵敏度最大值的曲线图存在着一定的对应关系，而从曲线上的每个点来说，土体应变灵敏度取到最大值时土体未完全破坏，土的结构强度没有得到完全释放，锥入度之比的每个值反映了原状土与重塑土抵抗剪切破坏的能力；在锥入度之比与应力灵敏度随饱和度变化的规律中，应力灵敏度的每个最大值变化不大，因此受饱和度变化的影响比较有限，而锥入度之比值随着饱和度的增加却呈现出先减小后增大的变化规律，因此锥入度之比受饱和度变化的影响比较明显。
[Abstract]:The structure of soil is a very important internal factor to determine the mechanical properties of soil. The sensitivity and cone penetration ratio of silt are studied by the unconfined compressive strength test and cone penetration test in this paper. And from these two aspects to analyze the soil structure change law when the soil is disturbed and the saturation changes. The experimental results show that:. 1) when silty soil is affected by soaking water, it can be seen from the law of sensitivity changing with saturation that soil saturation is the most sensitive when soil saturation is about 70%, and the sensitivity reaches the maximum at this time, and the strength of soil changes obviously before and after disturbance. Soil is liable to damage under external load. 2) in the analysis of the test results of strain sensitivity, it can be seen that the peak point of strain sensitivity changing with strain curve represents the time when cracks occur in undisturbed soil. The deformation of soil before peak point is plastic deformation. After the peak point the soil gradually loses its original structure. With the continuous development of cracks the gap between the compressive capacity of the undisturbed soil and the remolded soil becomes smaller and smaller and the corresponding stress ratio decreases gradually. 3) in the analysis of the test results of stress sensitivity, there is no peak point in the curve of stress sensitivity changing with strain, and the curve shows a monotone rising trend. With the increase of pressure, the deformation rate of undisturbed soil is larger than that of remolded soil. Therefore, the ratio of stress sensitivity under the same stress state is also increasing, and the curve also objectively reflects the effect of loading on soil structure. 4) from the comparative analysis of the three kinds of sensitivities, it can be seen that the strain sensitivity focuses on the structural strength of the soil, and the greater the ratio is, the greater the difference between the strength of the undisturbed soil and the remolded soil is. Therefore, the more sensitive the response of soil to external load before and after disturbance, the more sensitive the stress sensitivity is to the deformation ability of soil. The larger the ratio is, the faster the deformation rate of undisturbed soil with the same small increment of force is higher than that of the deformation of remolded soil. The strength ratio of the soil reflects the sensitivity of the soil. 5) in the numerical analysis of the ratio of cone penetration, the ratio of cone penetration decreases with the change of saturation from low to high, and the ratio reaches the minimum value at about 70%. Then the curve shows an upward trend with the increase of saturation, and the ratio of cone penetration is less than 1. The comparison and analysis of the ratio of cone penetration and three kinds of sensitivity show that the ratio of cone penetration to the commonly defined sensitivity has a corresponding relationship in the performance of soil structure, and the curve is approximately axisymmetric. The larger the sensitivity of soil is, the more obvious the structural strength of soil is, and the smaller the ratio of cone penetration is, the more obvious is the structural strength of soil, and on the whole, the ratio of cone penetration to the curve of maximum strain sensitivity has a certain corresponding relationship. From each point on the curve, when the strain sensitivity of the soil reaches the maximum, the soil is not completely destroyed, and the structure strength of the soil is not completely released. Each value of the ratio of cone penetration reflects the ability of the undisturbed soil and the remolded soil to resist shear failure. In the law that the ratio of cone penetration to stress sensitivity varies with saturation, each maximum value of stress sensitivity does not change much, so it is limited by the change of saturation. However, the ratio of cone penetration decreases first and then increases with the increase of saturation, so the ratio of cone penetration is obviously affected by the change of saturation.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411

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