Research On Saline Soil Subgrade Treatment Methods And Construction Technology

Saline soil has the basic engineering properties such as salt expansion,collapsibility and corrosiveness because the saline soil is affected by climateenvironment, regional distribution and hydro-geological conditions and other factors,and it causes a variety of subgrade and pavement diseases. Therefore, it is necessary tostudy saline soil in order to avoid or reduce the damage caused by saline soil.In this dissertation, treatment methods and construction technology of saline soilsubgrade were taken as the main line, and this paper relies on a accommodate highwayin northwesten area of China. The meteorology and hydrology, hydrogeology anddistribution and performance forms of subgrade diseases in new sections were givenbased on summarizing the engineering properties of saline soil. In addition, routinegeotechnical tests, mechanical properties tests of saline soil subgrade and durabilitytests were carried out combining with the engineering properties of saline soil subgradeto study the improvement mechanism of saline soil subgrade. Technical requirementsfor each improvement material were given through mixing different materials.Moreover, the influencing factors for salinization of soil and design principles ofsubgrade in saline soil area were proposed, and the treatment methods and constructiontechnology of subgrade of the supported project were determined.Through the above studies, the concrete results in this dissertation are as follows:(1) The distribution and performance forms of saline soil in new sections of thisaccommodate highway were obtained through investigation.(2) The influences of salinity on cohesion of saline soil, internal friction angle andshear strength of saline soil subgrade were gotten by tests in low-temperature state.(3) The changes of cohesion and internal friction angle in saline soil were gainedfrom the saline soil improved by lime and cement, and the influences of lime andcement on the compressive strength and water stability of saline soil subgrade weregotten as well.(4) The changes in compressive strength with age and the influences on the earlystrength and post-strength of saline soil were obtained after mixing lime.(5) The changes of compression rebound modulus with lime dosage were obtainedfrom the saline soil mixed with lime. In addition, the influence of cement on thecompressive rebound modulus and the roles to enhance the ability of resistancedeformation for improvement saline soil were gotten.(6) The influences of lime and cement on strength loss and the influences of cement on the durability of saline soil were compared to saline soil mixed with lime andcement through dry-wet cycles.(7) The influences of lime and cement on mass loss rate and the influences ofcement on the freezing resistance of saline soil subgrade were compared to saline soilmixed with lime and cement through freeze-thaw cycles.(8) The improvement mechanism of saline soil was received and the constructiontechnical requirements of improvement saline soil were determined by studying the limeimprovement saline soil.(9) The basical treatment schemes of saline soil subgrade from the supportedproject were determined and the concrete construction technologies were put forwardincluding the subgrade basement treatment, the embankment height and salinity controlto filling materials, cut-off layer settings of subgrade, protective measures of roadshoulder and other protective measures.