發(fā)布時間：2018-03-28 23:27

  本文選題：紅黏土　切入點：水土作用　出處：《廣西大學》2017年碩士論文

【摘要】：本文基于基礎(chǔ)底面墊砂后,基礎(chǔ)底面形成了儲水空間、形成了失水通道,為軟化基礎(chǔ)底面表層紅黏土提供了軟化交界面,同時也為紅黏土的失水收縮形成了收縮界面,可能對建(構(gòu))物產(chǎn)生危害。針對這一現(xiàn)象作者從室內(nèi)及室外設(shè)計一系列的模擬試驗研究,研究表明:1、模擬裂隙滲水試驗發(fā)現(xiàn),崩解、泥化、軟化的程度與紅黏土裂隙發(fā)育的程度直接相關(guān)。當持續(xù)高溫后降雨條件下,裂隙發(fā)育密而深,水流滲入造成一定地基深度內(nèi)紅黏土的崩解、泥化、軟化整體發(fā)生,形成軟弱層,造成地基承載力降低,變形量增大。當高溫與降雨交替的條件下,裂隙發(fā)育疏而淺,水流滲入地基的深度也比較淺,紅黏土的崩解、泥化、軟化沿豎向及水平向間隔發(fā)生,形成軟弱帶,造成地基承載力有一定的降低。裂隙開啟與閉合在平面上往復(fù)震蕩,裂隙并非出現(xiàn)在同一位置。水土作用下裂隙的開啟與閉合,反映了泥化軟化作用與固結(jié)作用交替進行。2、綜上對紅黏土物理力學指標的分析表明紅黏土存在以下特點:隨深度的增加,含水量逐漸增加,體現(xiàn)出“上干下濕”的特點;隨深度的增加,含水比逐漸增加,體現(xiàn)出“上硬下軟”的特點;隨深度的增加,孔隙比逐漸增加,體現(xiàn)出“上密下疏”的特點;隨深度的增加,黏聚力c逐漸減小,體現(xiàn)出抗剪強度“上大下小”的特點。3、浸泡吸水和蒸發(fā)失水,浸泡很快達到飽和,蒸發(fā)恢復(fù)到自然狀態(tài)下含水率,需要很長的時間。4、紅黏土遇水浸泡后,黏聚力初始降低幅度很大,當含水率達到飽和狀態(tài)時,其黏聚力降低至最低值后,不再發(fā)生變化。5、紅黏土浸水后浸水軟化,軟化的效果隨深度的增加而減弱,到一定臨界值后,土體基本不在受水浸泡的影響。通過測定不同深度的含水率變化,可以確定紅黏土的軟化深度,這一方法是簡單、快捷、可行的方法。6、紅黏土地基無論是否有荷載的作用,遇水浸泡后對“軟化臨界深度”范圍的紅黏土地基的承載力、變形模量、抗剪強度降低,軟化降低的幅度取決于浸泡時間。有荷載浸泡的,盡管不比無荷載情況的大,但承載力降低幅值也達10-20%,浸泡時間不同,軟化深度不同,但對建筑地基的危害是一樣存在的。變形模量的降幅比承載力的降幅大,變形模量的降低造成的危害要比承載力降低造成的危害要大。7、載荷試驗成果與輕型動力觸探試驗成果降低幅度基本一致�；坶_挖過程中,可采用輕型動力觸探分析遇水軟化強度降低幅度,為設(shè)計提供依據(jù)。8、根據(jù)室內(nèi)外的脹縮試驗,顯示室外測試的指標比室內(nèi)測試的指標大。根據(jù)室內(nèi)指標分析紅黏土膨脹性,是偏危險的。因此,本文提出對紅黏土的脹縮性評價,無論自由膨脹率的大小,只要膨脹總率大于1%或自由膨脹達到膨脹土的判定臨界值,都應(yīng)定為膨脹土,并對其進行脹縮性評價;對膨脹力的測試應(yīng)進行現(xiàn)場的膨脹力測試,修正目前紅黏土膨脹壓力的室內(nèi)測試方法。9、本文通過模擬試驗研究,紅黏土在水土作用下,一定深度內(nèi)的強度指標,均呈現(xiàn)了不同程度的降低,對建筑可能導(dǎo)致不利的危害。通過對案例的分析,也證實了紅黏土水土作用的軟化,承載力的降低幅度和試驗成果基本一致。對紅黏土的地基應(yīng)采取相應(yīng)的防治措施,避免建筑地基因水土作用影響建筑的使用功能、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.

【學位授予單位】：廣西大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU446

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