粗颗粒盐渍土路基冻融室内试验研究
发布时间：2018-07-31 12:50
【摘要】：G3011线(青海境)是我国第一条在内陆强盐渍土地区修建的高等级公路(简称察格高速公路),该公路从最大的内陆盐湖-察尔汗盐湖穿过,地基土主要为强~过盐渍土。此外,察尔汗盐湖地下水位高、年温差比较大。季节交换时,盐渍土在周期冻融作用下,水分和盐分会发生反复的迁移和积聚、结晶和溶解,造成各种道路和建筑物病害,严重影响道路建设和交通运营安全。为了改善察格高速的路用性能,防治路基病害,充分利用当地资源,考虑采用该公路沿线的粗颗粒弱盐渍土填筑路基。为了探究粗粒盐渍土冻融作用下的水盐迁移及力学性能变化情况,对察格高速沿线现场取样,进行了室内土工试验和冻融模拟试验。本文主要研究内容及结论如下:1.对天然状态下的粗粒盐渍土路基填料进行击实试验、颗粒分析试验和易溶盐测定试验。结果表明该土样的最佳含水率为8.5%,最大干密度为2.13g/cm3,易溶盐含量为0.542%,即该粗颗粒路基填料属于级配不良弱盐渍化砾类土。2.砾类盐渍土路基经历不同冻融循环后,其水分在高度方向上呈“抛物线”型分布,水分含量及其分布曲线的曲率均随路基高度的增加而逐渐降低。40cm以下的土层水分迁移在冻融前期波动性较大;40cm以上的土层水分受冻融作用的影响较小,水分随着冻融周期增加向上持续迁移;10cm及70cm处的土层作为水分补给源,含水率随着周期的增加而降低。3.砾类土路基的盐分迁移通道形成过程较复杂且历时长。前两次冻融循环过程中,路基内部的盐分迁移通道尚未完全贯通,盐分迁移主要发生于路基的局部土层;从第三次冻融循环开始,路基高度方向上逐渐形成连续性的盐分迁移通道,砾类土路基中的盐分开始整体性地迁移和积聚,盐分分布曲线以40cm和70cm处的土层为界点呈现“三段式”的波浪形。4.将原状土样和经历不同冻融周期后积盐量最大的土层,进行回弹模量和承载比试验。试验表明,砾类土路基冻融积盐后,E0和CBR值随着积盐量的增加而均变小,砾类土路基承载性能有所降低。
[Abstract]:Line G3011 (Qinghai border) is the first high grade highway (Chage Expressway) built in the inland strong saline soil area of China. The highway passes through the largest inland salt lake-Qarhan Salt Lake. The foundation soil is mainly strong to super saline soil. In addition, Chaerhan Salt Lake groundwater level is high, the annual temperature difference is relatively large. During the seasonal exchange, under the action of periodic freezing and thawing, the water and salt branches repeatedly migrate and accumulate, crystallize and dissolve, resulting in a variety of road and building diseases, which seriously affect the road construction and traffic safety. In order to improve the road performance of Chage high speed, prevent and cure roadbed diseases and make full use of local resources, the coarse grain weak saline soil along the highway is considered to be used to fill the roadbed. In order to investigate the changes of water and salt migration and mechanical properties of coarse saline soil under freezing and thawing the field sampling along Chage high speed was carried out in laboratory and freeze-thaw simulation tests. The main contents and conclusions of this paper are as follows: 1. Compaction test, particle analysis test and soluble salt determination test were carried out for subgrade fillers of coarse saline soil in natural state. The results show that the optimum moisture content of the soil sample is 8.5, the maximum dry density is 2.13g / cm ~ 3, and the soluble salt content is 0.542, that is, the coarse grain subgrade filling belongs to the gradation of poor gradation and weak salinized gravel soil. After different freeze-thaw cycles, the water content of gravel saline soil subgrade is "parabola" distribution in height direction. The curvature of water content and its distribution curve decreased gradually with the increase of the height of roadbed. The moisture migration of soil layer below .40cm was less affected by freezing and thawing than that of soil layer above 40cm in the early stage of freezing and thawing. With the increase of freezing and thawing cycle, the soil layer at 10cm and 70cm is used as the water supply source, and the moisture content decreases with the increase of the period. The formation process of salt migration passage of gravel subgrade is complex and long. During the first two freeze-thaw cycles, the salt transfer passage within the roadbed has not been fully completed, and the salt migration mainly occurs in the local soil layer of the roadbed, beginning with the third freeze-thaw cycle. In the direction of roadbed height, a continuous salt migration passage is gradually formed, and the salt in the gravel subgrade begins to migrate and accumulate as a whole. The salt distribution curve takes the soil layer at 40cm and 70cm as the boundary point and presents a "three-section" wavy shape. The elastic modulus and bearing ratio of the undisturbed soil samples and the soil layers with the largest salt content after different freezing and thawing cycles were tested. The test results show that the values of E0 and CBR of gravel subgrade decrease with the increase of salt content, and the bearing capacity of gravel subgrade decreases.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.16
本文编号：2155634
[Abstract]:Line G3011 (Qinghai border) is the first high grade highway (Chage Expressway) built in the inland strong saline soil area of China. The highway passes through the largest inland salt lake-Qarhan Salt Lake. The foundation soil is mainly strong to super saline soil. In addition, Chaerhan Salt Lake groundwater level is high, the annual temperature difference is relatively large. During the seasonal exchange, under the action of periodic freezing and thawing, the water and salt branches repeatedly migrate and accumulate, crystallize and dissolve, resulting in a variety of road and building diseases, which seriously affect the road construction and traffic safety. In order to improve the road performance of Chage high speed, prevent and cure roadbed diseases and make full use of local resources, the coarse grain weak saline soil along the highway is considered to be used to fill the roadbed. In order to investigate the changes of water and salt migration and mechanical properties of coarse saline soil under freezing and thawing the field sampling along Chage high speed was carried out in laboratory and freeze-thaw simulation tests. The main contents and conclusions of this paper are as follows: 1. Compaction test, particle analysis test and soluble salt determination test were carried out for subgrade fillers of coarse saline soil in natural state. The results show that the optimum moisture content of the soil sample is 8.5, the maximum dry density is 2.13g / cm ~ 3, and the soluble salt content is 0.542, that is, the coarse grain subgrade filling belongs to the gradation of poor gradation and weak salinized gravel soil. After different freeze-thaw cycles, the water content of gravel saline soil subgrade is "parabola" distribution in height direction. The curvature of water content and its distribution curve decreased gradually with the increase of the height of roadbed. The moisture migration of soil layer below .40cm was less affected by freezing and thawing than that of soil layer above 40cm in the early stage of freezing and thawing. With the increase of freezing and thawing cycle, the soil layer at 10cm and 70cm is used as the water supply source, and the moisture content decreases with the increase of the period. The formation process of salt migration passage of gravel subgrade is complex and long. During the first two freeze-thaw cycles, the salt transfer passage within the roadbed has not been fully completed, and the salt migration mainly occurs in the local soil layer of the roadbed, beginning with the third freeze-thaw cycle. In the direction of roadbed height, a continuous salt migration passage is gradually formed, and the salt in the gravel subgrade begins to migrate and accumulate as a whole. The salt distribution curve takes the soil layer at 40cm and 70cm as the boundary point and presents a "three-section" wavy shape. The elastic modulus and bearing ratio of the undisturbed soil samples and the soil layers with the largest salt content after different freezing and thawing cycles were tested. The test results show that the values of E0 and CBR of gravel subgrade decrease with the increase of salt content, and the bearing capacity of gravel subgrade decreases.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.16
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