【摘要】：G3011線(青海境)是我國第一條在內(nèi)陸強(qiáng)鹽漬土地區(qū)修建的高等級(jí)公路(簡稱察格高速公路),該公路從最大的內(nèi)陸鹽湖-察爾汗鹽湖穿過,地基土主要為強(qiáng)~過鹽漬土。此外,察爾汗鹽湖地下水位高、年溫差比較大。季節(jié)交換時(shí),鹽漬土在周期凍融作用下,水分和鹽分會(huì)發(fā)生反復(fù)的遷移和積聚、結(jié)晶和溶解,造成各種道路和建筑物病害,嚴(yán)重影響道路建設(shè)和交通運(yùn)營安全。為了改善察格高速的路用性能,防治路基病害,充分利用當(dāng)?shù)刭Y源,考慮采用該公路沿線的粗顆粒弱鹽漬土填筑路基。為了探究粗粒鹽漬土凍融作用下的水鹽遷移及力學(xué)性能變化情況,對(duì)察格高速沿線現(xiàn)場取樣,進(jìn)行了室內(nèi)土工試驗(yàn)和凍融模擬試驗(yàn)。本文主要研究內(nèi)容及結(jié)論如下:1.對(duì)天然狀態(tài)下的粗粒鹽漬土路基填料進(jìn)行擊實(shí)試驗(yàn)、顆粒分析試驗(yàn)和易溶鹽測定試驗(yàn)。結(jié)果表明該土樣的最佳含水率為8.5%,最大干密度為2.13g/cm3,易溶鹽含量為0.542%,即該粗顆粒路基填料屬于級(jí)配不良弱鹽漬化礫類土。2.礫類鹽漬土路基經(jīng)歷不同凍融循環(huán)后,其水分在高度方向上呈“拋物線”型分布,水分含量及其分布曲線的曲率均隨路基高度的增加而逐漸降低。40cm以下的土層水分遷移在凍融前期波動(dòng)性較大;40cm以上的土層水分受凍融作用的影響較小,水分隨著凍融周期增加向上持續(xù)遷移;10cm及70cm處的土層作為水分補(bǔ)給源,含水率隨著周期的增加而降低。3.礫類土路基的鹽分遷移通道形成過程較復(fù)雜且歷時(shí)長。前兩次凍融循環(huán)過程中,路基內(nèi)部的鹽分遷移通道尚未完全貫通,鹽分遷移主要發(fā)生于路基的局部土層;從第三次凍融循環(huán)開始,路基高度方向上逐漸形成連續(xù)性的鹽分遷移通道,礫類土路基中的鹽分開始整體性地遷移和積聚,鹽分分布曲線以40cm和70cm處的土層為界點(diǎn)呈現(xiàn)“三段式”的波浪形。4.將原狀土樣和經(jīng)歷不同凍融周期后積鹽量最大的土層,進(jìn)行回彈模量和承載比試驗(yàn)。試驗(yàn)表明,礫類土路基凍融積鹽后,E0和CBR值隨著積鹽量的增加而均變小,礫類土路基承載性能有所降低。
[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.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：U416.16

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