隔水透气隔断层对寒旱区盐渍土水盐迁移及变形特性的影响

Research on the influence of water and salt migration and deformation characteristics of saline soil in cold and arid regions by water and breathable separation layer

针对寒旱区盐渍土水盐迁移引起的盐冻胀变形病害问题,本研究提出了一种新型的隔水透气膜隔断层处理方法,并开展了相应的理论分析和室内试验研究。基于多孔介质理论和连续介质力学理论,通过考虑温度变化下孔隙水盐相变等因素,建立了非饱和盐渍土的水-热-盐-力多场多相耦合模型。在水盐补给条件下,采用数值模拟和室内模型试验研究了非饱和硫酸盐渍土的水盐迁移和盐冻胀变形特性,并验证了模型的有效性。重点分析了设置隔水透气膜对非饱和硫酸盐渍土热质迁移及变形行为的影响。研究结果表明:隔水透气层对液态水和溶解盐的迁移具有明显的阻滞作用。同时,由于隔断层的透气特性,可有效地解决传统土工膜隔断层下气体聚集现象。研究成果可为盐渍土路基处理提供技术与理论基础。

In recent years,under the“Belt and Road”initiative and the“transportation power”strategy actively promoted by China,the transportation infrastructure in the cold and arid regions of northwest China has been strengthened.As these constructions progress,it was inevitable to cross sections of saline soil,which created a series of challenges and problems for the construction and maintenance of the area.Problems caused by saline soils can not only be problematic during construction,but also have an impact on the long-term maintenance and operation of the facility.In the cold and arid regions of northwest China,the distribution of saline soils poses considerable challenges to infrastructure construction.In these areas,sulfate saline soil,as the most representative saline soil,exhibits a particularly obvious salt frost heave phenomenon when the temperature changes.The fluctuation of temperature,humidity and salt concentration in sulfated saline soil will cause salt heave and frost heave in the subgrade of sulfate saline soil,resulting in uneven uplift,structural relaxation and cracks on the pavement.These diseases not only affect the structural strength and stability of the roadbed,but also may cause hidden dangers to traffic safety and increase the risk of traffic accidents.In view of this,researchers and engineers have been exploring effective treatment technologies and methods to mitigate or eradicate the negative effects of saline soil.Among the many solutions,geopartition technology has been widely recognized and adopted for its economy and practicality.On this basis,this study proposes an innovative water-permeable membrane partition treatment technology,which aims to effectively control the movement of water and salt in saline soil by means of physical isolation and reduce the structural deformation and damage caused by salt frost heave.Based on the theory of porous medium and continuum media,and considering the effects of temperature change and water-salt recharge conditions on the water-salt phase transition in soil pores,a comprehensive water-heat-salt-force multi-field multiphase coupling mathematical model was established.The model covers a variety of transport mechanisms such as the movement of liquid water and water vapor,the diffusion and convection of solutes,the heat conduction,and the mechanical response of soil,which can accurately describe the complex interactions in unsaturated saline soil systems and predict the dynamic behavior of water and salt under actual conditions.In order to verify the effectiveness of the model,numerical simulation technology and laboratory model tests were used to study the water-salt migration law and salt heave deformation characteristics of unsaturated sulfate saline soil under the condition of simulating natural water and salt recharge under the condition of simulating natural water and salt recharge.By comparing the numerical simulation results with the laboratory test data,the accuracy and practicability of the model are confirmed,which provides a solid theoretical foundation for engineering application.In this study,the effects of the water-insulated and breathable membrane on the thermal migration and deformation behavior of unsaturated sulfate saline soil were analyzed.The experimental and numerical simulation results show that the water-permeable layer can significantly inhibit the vertical migration of liquid water and dissolved salts,and effectively prevent secondary salinization and structural damage of soil.In addition,the air permeability of the waterproof air permeable layer solves the problem of gas accumulation under the traditional geomembrane,and avoids the additional engineering problems caused by gas accumulation.In short,the results of this study not only provide a new technical scheme for the treatment of saline soil subgrade in cold and arid areas and other similar areas,but also provide a set of theoretical basis for engineering designers to refer to.The implementation of this new waterproof and breathable membrane treatment technology will significantly improve road stability,prolong the service life of roadbed,and reduce maintenance costs,which has important engineering practice value and wide application prospects.