基于水土作用下红黏土的力学特性研究

发布时间：2018-03-28 23:27

本文选题：红黏土　切入点：水土作用　出处：《广西大学》2017年硕士论文

【摘要】：本文基于基础底面垫砂后,基础底面形成了储水空间、形成了失水通道,为软化基础底面表层红黏土提供了软化交界面,同时也为红黏土的失水收缩形成了收缩界面,可能对建(构)物产生危害。针对这一现象作者从室内及室外设计一系列的模拟试验研究,研究表明:1、模拟裂隙渗水试验发现,崩解、泥化、软化的程度与红黏土裂隙发育的程度直接相关。当持续高温后降雨条件下,裂隙发育密而深,水流渗入造成一定地基深度内红黏土的崩解、泥化、软化整体发生,形成软弱层,造成地基承载力降低,变形量增大。当高温与降雨交替的条件下,裂隙发育疏而浅,水流渗入地基的深度也比较浅,红黏土的崩解、泥化、软化沿竖向及水平向间隔发生,形成软弱带,造成地基承载力有一定的降低。裂隙开启与闭合在平面上往复震荡,裂隙并非出现在同一位置。水土作用下裂隙的开启与闭合,反映了泥化软化作用与固结作用交替进行。2、综上对红黏土物理力学指标的分析表明红黏土存在以下特点:随深度的增加,含水量逐渐增加,体现出“上干下湿”的特点;随深度的增加,含水比逐渐增加,体现出“上硬下软”的特点;随深度的增加,孔隙比逐渐增加,体现出“上密下疏”的特点;随深度的增加,黏聚力c逐渐减小,体现出抗剪强度“上大下小”的特点。3、浸泡吸水和蒸发失水,浸泡很快达到饱和,蒸发恢复到自然状态下含水率,需要很长的时间。4、红黏土遇水浸泡后,黏聚力初始降低幅度很大,当含水率达到饱和状态时,其黏聚力降低至最低值后,不再发生变化。5、红黏土浸水后浸水软化,软化的效果随深度的增加而减弱,到一定临界值后,土体基本不在受水浸泡的影响。通过测定不同深度的含水率变化,可以确定红黏土的软化深度,这一方法是简单、快捷、可行的方法。6、红黏土地基无论是否有荷载的作用,遇水浸泡后对“软化临界深度”范围的红黏土地基的承载力、变形模量、抗剪强度降低,软化降低的幅度取决于浸泡时间。有荷载浸泡的,尽管不比无荷载情况的大,但承载力降低幅值也达10-20%,浸泡时间不同,软化深度不同,但对建筑地基的危害是一样存在的。变形模量的降幅比承载力的降幅大,变形模量的降低造成的危害要比承载力降低造成的危害要大。7、载荷试验成果与轻型动力触探试验成果降低幅度基本一致。基槽开挖过程中,可采用轻型动力触探分析遇水软化强度降低幅度,为设计提供依据。8、根据室内外的胀缩试验,显示室外测试的指标比室内测试的指标大。根据室内指标分析红黏土膨胀性,是偏危险的。因此,本文提出对红黏土的胀缩性评价,无论自由膨胀率的大小,只要膨胀总率大于1%或自由膨胀达到膨胀土的判定临界值,都应定为膨胀土,并对其进行胀缩性评价;对膨胀力的测试应进行现场的膨胀力测试,修正目前红黏土膨胀压力的室内测试方法。9、本文通过模拟试验研究,红黏土在水土作用下,一定深度内的强度指标,均呈现了不同程度的降低,对建筑可能导致不利的危害。通过对案例的分析,也证实了红黏土水土作用的软化,承载力的降低幅度和试验成果基本一致。对红黏土的地基应采取相应的防治措施,避免建筑地基因水土作用影响建筑的使用功能、安全及耐久性,作者提出了一些防治措施。
[Abstract]:This paper is based on the bottom surface of sand cushion, the bottom surface of the foundation formed a water storage space, the formation of water channel, provides the interface for softening softening of foundation bottom surface of red clay, but also the formation of a contraction interface for the shrinkage of red clay, on building (structure) from harm. The research showed that according to the author this phenomenon from indoor and outdoor design simulation study, a series of: 1, simulation of crack seepage test, collapse, mud, directly related to the degree of softening and red clay fracture development degree. When continued after high temperature under the condition of rainfall, fracture density and deep water infiltration caused by the disintegration of a red clay the foundation within the depth of mud, softening the whole, forming the soft layer, decrease the bearing capacity of foundation and deformation increases. When the high temperature and rainfall alternating conditions, sparsely fractured and shallow, seeping into the depth of the foundation is relatively shallow, red clay Soil disintegration, mud, softening occurs to the intervals along the vertical and horizontal, forming a weak zone, caused by foundation could reduce the bearing capacity of crack opening and closing in the plane of reciprocating concussion, fracture did not appear in the same location. The opening and closure of the cracks under the action of water and soil, reflects the mud softening effect and consolidation effect of alternating.2, analysis of physical and mechanical indexes of red clay in that red clay has the following characteristics: with the increase of depth, the water content increased gradually, embody the characteristics of "wet"; with the increase of depth, the ratio is gradually increased, reflecting the characteristics of "hard soft"; with the the increase of depth, the void ratio increases gradually, reflecting the characteristics of "under the secret"; with the increase of depth, the cohesion c decreased gradually, reflect the shear strength of.3 characteristics of large small ", water evaporation and loss of water, soaking soon reach saturation And, to restore moisture evaporation under natural conditions, take a long time.4, the red clay after soaking in water, the initial cohesion reduces greatly, when the water content reaches saturation, the cohesion decreases to the lowest value after the change,.5 no longer occurs, water softening red clay after soaking, increased softening the effect of reduced with depth, to a certain critical value, the soil basically not affected by water immersion. Rate of change by water content in different depth, can determine the depth of softening of red clay, this method is simple, fast,.6 method is feasible, whether there is a red clay ground load after soaking in water, to soften the critical depth of the scope of the red clay foundation bearing capacity, deformation modulus, shear strength decreased, the decrease amplitude depends on the softening in the soaking time. Load soaking, though not without load than large, but the bearing capacity drop Low amplitude of 10-20%, different soaking time, softening depth is different, but the damage to the building foundation is existed. The deformation modulus of the decline over the bearing capacity of the large decline, the deformation modulus reduces the harm to the harm to.7 lower than the bearing capacity, load test results and test results of light dynamic penetration reduction is basically the same. In the process of excavation, the light dynamic penetration analysis of water softening strength decrease, and provide the basis for the design of.8, according to the expansion test, display outdoor test index than indoor test indexes. According to the index analysis of red clay swelling, it is dangerous. So in this paper, the red clay expansion evaluation, regardless of the size of the free expansion rate of expansion, as long as the total rate of greater than 1% or the free expansion of the expansive soil to determine the critical value, should be set for the expansive soil, and the The expansion of evaluation; swelling force tests shall be carried out in the expansive force test, indoor test method at present modified red clay swelling pressure.9, through simulation test, the red clay in the soil under the action of strength in certain depth, showed a different degree of decrease of construction may lead to adverse harm. Through the analysis of the case, also confirmed that the red clay soil softening effect, bearing capacity decreases and the test results are basically the same. The red clay foundation should take appropriate preventive measures to avoid the building foundation for soil influence the use function of the building, safety and durability, the author puts forward some preventive measures.

【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU446

【参考文献】