蒙自绕城高速公路工程膨胀土路基改良方案研究

发布时间：2019-04-21 09:33

【摘要】：近几十年来,随着工程施工技术水平的提高,越来越多的国家在施工过程中遇到膨胀土危害问题。本文涉及的实际工程项目为自绕城高速公路(羊鸡段),羊鸡段全线土质均为膨胀土。膨胀土作为一种多缝隙并具有显著膨胀性的土体,吸水膨胀、失水收缩是其典型特性,在工程界中常常被认定为隐形的地质灾害,其对工程结构具有较为严重的破坏作用,这在高等级公路路基工程中尤为突出,其对公路往往会产生长期的变形破坏作用。为此,本文通过选取石灰改良膨胀土,结合室内击实试验、CBR试验以及胀缩性试验,对石灰改良膨胀土方案的有效性展开研究,得出主要结论如下:(1)在击实试验中,随着含水率从17.2%增加至26.1%,对应的干密度呈先增大后减小的抛物线变化,即从1.57g/cm3先增大至1.65 g/cm3,随后逐渐减小至1.57 g/cm3,从而确定最佳含水量为21.3%,对应的最大干密度为1.65 g/cm3。(2)CBR试验中,当每层击实30次时,试验组1~3的单位压力与贯入量的变化关系基本一致,即随着单位压力的逐渐增加,贯入量逐渐增大,且增大趋势逐渐加快。3个试验组中贯入量为2.5mm时对应的单位压力分别为532k Pa、566k Pa、538k Pa,与之对应的CBR值分别为7.6%、8.1%、7.7%;贯入量为5mm时对应的单位压力分别为709k Pa、763k Pa、750Pa,与之对应的CBR值分别为6.8%、7.3%、7.1%;当每层击实50次时,试验组4~6的单位压力与贯入量的变化关系基本一致,即随着单位压力的逐渐增加,贯入量逐渐增大,且增大趋势逐渐加快。3个三个试验组中贯入量为2.5mm时对应的单位压力分别为733k Pa、733k Pa、738k Pa,与之对应的CBR值分别为10.5%、10.5%、10.5%;贯入量为5mm时对应的单位压力分别为1079k Pa、1066k Pa、1074Pa,与之对应的CBR值分别为10.3%、10.2%、10.2%;当每层击实98次时,试验组7~9的单位压力与贯入量的变化关系基本一致,即随着单位压力的逐渐增加,贯入量逐渐增大,且增大趋势逐渐加快。3个试验组中贯入量为2.5mm时对应的单位压力分别为829k Pa、808k Pa、816k Pa,与之对应的CBR值分别为11.8%、11.5%、11.7%;贯入量为5mm时对应的单位压力分别为1129k Pa、1130k Pa、1132Pa,与之对应的CBR值分别为10.8%、10.8%、10.8%。(3)CBR试验中,随着每层土的击实次数的增加,土样干密度逐渐增大,对应l=2.5mm以及l=5mm的CBR值也随之增大,且不同贯入度条件下CBR值相差不大,贯入度为2.5mm对应的CBR值始终大于贯入度为5mm对应的CBR值;且随着干密度增加,各贯入度对应的CBR值的增大趋势基本保持一致,当击实次数为50、98时,其CBR值满足路基填土使用要求。(4)胀缩性试验中,当每层击实次数由30、50变化至98次时,其对应的膨胀量均很低,均小于4%。随着击实次数的增加,试样对应的干密度逐渐增大,试样泡水后膨胀量亦呈增加趋势,且变化基本呈线性增加。
[Abstract]:In recent decades, with the improvement of engineering construction technology, more and more countries have encountered expansive soil hazards in the construction process. The actual project involved in this paper is the self-winding city highway (Yangji section), the whole line of soil in Yangji section is expansive soil. Expansive soil, as a kind of soil with multi-crevice and obvious expansibility, is a typical characteristic of expansive soil, which is characterized by water absorption and shrinkage. It is often regarded as an invisible geological hazard in the engineering field, and it has a serious damage to the engineering structure. This is especially prominent in the high-grade highway roadbed engineering, which often has a long-term deformation and damage effect on the highway. Therefore, through selecting lime to improve expansive soil, combining with laboratory compaction test, CBR test and expansion-shrinkage test, this paper studies the effectiveness of lime-modified expansive soil scheme. The main conclusions are as follows: (1) in compaction test, the results are as follows: (1) in compaction test, the effectiveness of lime-modified expansive soil scheme is studied. With the increase of moisture content from 17.2% to 26.1%, the corresponding dry density increases first and then decreases, that is, from 1.57g/cm3 to 1.65 g / cm ~ 3, then to 1.57g/cm3. The optimum moisture content is 21.3%, and the corresponding maximum dry density is 1.65 g / cm ~ 3 (2) CBR test. When each layer is compacted 30 times, the relationship between the unit pressure and the penetration amount of the test group is basically consistent. That is, with the gradual increase of the unit pressure, the penetration rate gradually increased and the increasing trend gradually accelerated. The unit pressure corresponding to the penetration of 2.5mm in the three test groups was 532k / Pa,566k Pa,538k Pa, respectively. The corresponding CBR values were 7.6%, 8.1% and 7.7%, respectively. When the penetration rate is 5mm, the corresponding unit pressure is 709k / Pa,763k Pa,750Pa, and the corresponding CBR values are 6.8%, 7.3%, 7.1%, respectively. When each layer is compacted 50 times, the relationship between unit pressure and penetration of test group 4? 6 is basically consistent, that is, with the gradual increase of unit pressure, the penetration quantity increases gradually. The unit pressure corresponding to 2.5mm was 733k / Pa,733k Pa,738k Pa, and the corresponding CBR values were 10.5%, 10.5% and 10.5%, respectively, when the penetration rate was 733k / mol in each of the three test groups and the corresponding CBR values were 10.5%, 10.5% and 10.5%, respectively. When the penetration rate is 5mm, the corresponding unit pressure is 1079 k / Pa,1066k Pa,1074Pa, and the corresponding CBR values are 10.3%, 10.2%, 10.2%, respectively. When each layer is compacted 98 times, the relationship between unit pressure and penetration of test group 7 ~ 9 is basically the same, that is, with the gradual increase of unit pressure, the penetration quantity increases gradually. The corresponding unit pressure of 829k 2.5mm was 11.8%, 11.5% and 11.7% respectively when the penetration rate was 829k / Pa,808k Pa,816k Pa,. The relative CBR values were 11.8%, 11.5% and 11.7% respectively. The unit pressure corresponding to the penetration of 5mm was 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8%, 10.8% The dry density of soil samples increases gradually, and the CBR value of corresponding l=2.5mm and l=5mm increases, and there is little difference in the value of CBR under different penetration degree. The value of CBR corresponding to 2.5mm is always greater than the value of CBR corresponding to the penetration degree of 5mm, and the value of CBR corresponding to penetration degree is always higher than the value of CBR corresponding to penetration degree. And with the increase of dry density, the increasing trend of CBR value corresponding to each penetration degree remains basically the same. When the number of compaction is 50,98, the CBR value meets the requirements of subgrade filling. (4) in the expansion and shrinkage test, the CBR value meets the requirements of roadbed filling. (4) expansion and shrinkage test. When the compaction times of each layer change from 30, 50 to 98 times, the corresponding expansion amount is very low, all of which are less than 4%. With the increase of the number of compaction, the corresponding dry density of the sample gradually increased, and the expansion of the sample after bubble water also showed an increasing trend, and the change basically showed a linear increase.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.167

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