【作者】 刘凯；

【导师】 张远芳； 慈军；

【作者基本信息】 新疆农业大学 ， 水利水电工程， 2017， 硕士

【摘要】 新疆地处内陆寒旱区,盐渍土在新疆分布广泛,不同区域的盐渍土又具有独特的性质。选取罗布泊地区和艾丁湖地区天然盐渍土进行不同降温速率条件下的盐冻胀试验和阶梯式冻融循环试验,研究降温速率对盐渍土盐冻胀特性的影响以及盐渍土冻融循环后盐冻胀规律和溶陷规律。主要结论如下:(1)罗布泊地区的亚氯盐渍土的盐冻胀量随温度的降低而不断增加,主要盐冻胀量产生的温度区间为-5℃～-25℃。而艾丁湖地区的亚硫酸盐渍土起胀温度较高,20℃时就有明显的盐胀变形,产生盐冻胀量较大的温度区间15℃～-5℃,而当温度在-15℃之后盐冻胀现象趋于平缓了,且最终的盐冻胀量很大,总体上罗布泊地区盐渍土盐冻胀量小于艾丁湖地区。(2)盐渍土的盐冻胀率随着降温速率的降低而呈幂指函数规律增长。当降温速率小,降温梯度也小,随着降温过程持续水盐的微迁移不断发生,产生的盐冻胀量较大,反之盐冻胀量较小。(3)艾丁湖地区氯盐渍土在冻融循环作用下,盐冻胀过程具有较好的累加效应。在最优含水率条件下经历9次冻融循环后最大盐胀量可达到约42mm,具有强盐胀性。在温度升高的阶段,盐冻胀量有所回落,但并不会恢复到初始的平衡状态。(4)艾丁湖地区氯盐渍土发生剧烈盐冻胀现象的温度区间是5℃～-15℃,而发生溶陷变形较大的温度区间是5℃～15℃。温度升高时产生的溶陷变形没有明显规律,不同含水率条件下发生最大溶陷变形的周期不同,盐冻胀增量较大的周期也不同。最优含水率时前3周期盐冻胀增量较大,可达到总盐冻量的68%。在最优含水率附近,盐冻胀量经历9次冻融循环后趋于稳定,而含水率远远大于最优含水率时,累加盐冻胀量在第9次冻融循环后仍在增加。(5)盐渍土中产生盐冻胀量多少是由盐渍土中含盐溶液存在于土样中的位置和土样颗粒之间的黏聚力、内摩擦力、相互引力等多种因素共同所决定的。温度的降低与升高是影响盐胀产生的主要原因。更多还原

【Abstract】 Xinjiang is located in inland of cold and arid areas,where saline soil is widely distributed.The saline soil of different regions has unique properties.The natural saline soil from Lop nur and Aydingkol Lake area as the experimental soil is selected to do the salt-frost heaving test and stepwise freeze-thaw cycling test under different cooling rate,to study the influence of cooling rate on the salt-frost heaving characteristics and the law of salt-frost heaving and dissolved collapse deformation after freez-thaw cycles.The main conclusions are as follows:(1)The amount of salt-frost heaving of the sub-chlorine saline soil in lop nur area increases with the decreasing of temperature,the temperature interval of the main salt-frost heaving is from -5℃ to -25℃.While sulfurous acid saline soil of Aydingkol Lake starts to bulge at higher temperature,there is obvious deformation of salt expansion at 20℃,and the temperature interval of the main salt frost heaving is from 15℃ to -5℃.When the temperature is below -15℃,the salt frost heaving tends to be gentle,and the final salt frost heaving is very large.Overall the salt frost heaving of saline soil in the area of Lop Nur is less than that of Aiding Lake.(2)The increase of salt heaving rate of saline soil shows the power exponential function with the decrease of the cooling rate.When the cooling rate is small,the cooling gradient is also small,the micro-migration of water and salt occurs continuously during the cooling process,resulting in the large amount of salt frost swelling,or the lower the amount of salt swelling.(3)The salt frost heaving process of chlorine soil saline in the Aydingkol Lake area has good accumulative effect under the freeze-thaw cycle.Under the condition of optimum water content,the maximum salt expansion can reach to 42 mm after 9 freeze-thaw cycles.In the stage of rising temperature,the salt frost heaving drops,but it will not return to the initial equilibrium state.(4)The temperature range of violent salt frost heaving phenomenon of chlorine saline soil in Aydingkol Lake area is from 5℃ to -15℃,and the temperature range of the larger dissolved collapse deformation is from 5℃ to 15℃.There are no obvious laws of deformation when the temperature rises.Under different water content,the period of maximum deformation and the period of large increase in salt swelling are different.In the first 3 cycles,the salt frost heaving amount increases greatly,which can reach to 68% of the total salt heaving.In the vicinity of the optimal water content,the salt frost heaving tends to be stable after 9 freeze-thaw cycles.While the water content is much larger than the optimal water content,the accumulative salt heaving is still increasing after 9 freez-thaw cycles.(5)The amount of salt frost heaving in saline soil is determined by many factors,such as the location of salt solution in saline soil,the cohesive force,internal friction force and gravitational attraction between soil particles.The decrease and increase of temperature is the main reason of salt expansion.更多还原