Study On Reinforced Performance Of Geogrids In Seasonal Frozen Soil

The frozen soil is harmful to road construction of our country,when the soil is frozen although its strength improved,but the volume expansion in the process of freezing,leading to uplift and deformation of road subgrade;The role of skeleton support in ice and soil is disappeared after thawing,which leads to the reduction of the volume and the decrease of the bearing capacity of the foundation,the roadbed sinking fall under the vehicle load,resulting in uneven road surface,and even local fall,it is a serious threat to the traffic and transportation safety of our country.Geogrid has a unique network structure.Depending on the occluding and interlocking between geogrid and soil friction and mesh generated,improving the soil strength and deformation characteristics effectively,so as to improve the stability of geogrid reinforced soil.In order to know about the reinforced performance of geogrid in seasonal frozen soil,the main investigations and achievements in this paper are composed of following portions:The liquid plastic limit test was conducted obtaining liquid limit and plastic limit,the compaction test was conducted obtaining the maximum dry unit weight and optimum moisture content,the grain size distribution test was conducted obtaining the grain size distribution curve.Based on the grain size distribution analysis and plastic index,the soil is named as silty clay.The integrated test system about geosynthetics called TZY-1 was used in this investigation,a series of indoor geogrid pullout test was conducted revealing the influence of different water content and freeze-thaw cycle on pullout behavior of geogrid.Studied on the reinforcement mechanism of geogrid and the interaction between the geogrid and the soil,the test data were compared and analyzed systematically.The test results show that water content has great influence on the pullout test,the pullout friction coefficient decrease with the increase of moisture content.The effect of freeze-thaw cycles on the pull-out test is not obvious,the analysis of geogrid transverse ribs and longitudinal rib reinforcement mechanism,verify the geogrid as reinforced materials help inhibition of seasonal frozen soil freezing thawing soil structure damage.A series of experiment to investigate the resistance mechanism of longitudinal ribs are performed with TZY-1 pullout devices under different water content and freeze-thaw cycle.Studied on the reinforcement mechanism of transverse and longitudinal ribs.The test results show that the interface friction angle between longitudinal ribs and soil decreases with the increase of water content,with the increase of the number of freeze-thaw cycles,the interfacial friction coefficient may increase and decrease there is no obvious change trend.A series of frost heave test was conducted to obtain the frost heave and thaw settlement of soil during freezing thawing cycles,the regression equation was established by analyzing the law of correlation characteristic value change.A comparative analysis was carried out between the geogrid and without geogrid in the sample.The test results show that the frost heave amount of the soil sample without the geogrid can reach 1.56 times of the frost heave of the geogrid,the frost heave laying geogrid decreased obviously.The frost heave(thaw settlement)of soil increases with the increase of water content,there is a linear relationship between frost heave(thaw settlement)and water content,the correlation coefficient of the linear fitting curve of frost heave is less than that of the linear fitting curve of thaw settlement,the settlement of soil is more sensitive to the change of water content.