Slightly Dense Gravel Soil Foundation Of Analysis Of The Mechanical Properties And Engineering Practice

As a kind of common soil and gravel soil,with many engineering characteristics,its influence is various.However,there are less research about the mechanical properties of the crushed stone soil with large Particle size,siltycly and slightly dense state.This type of gravelly soil is widely distributed in Northeast Chongqing,as the main geological environment and important construction material of the foundation of the building in this area,the engineering properties of the slightly crushed stone soil can not be ignored in the construction of the project.The formation of gravelly soil in this area has its unique physical and dynamics characteristics due to its different geographical,climatic and hydrogeological conditions.The process of the formation of gravelly soil has its unique characteristics due to its different geographical,climatic and hydrogeological conditions.Generally,the gravelly soil has the advantages of high bearing capacity and low compressibility,and is a better natural foundation.Owing to the lack of research on the engineering properties of silty gravel filled with silty clay in this area,even in the construction of low and middle layers with low bearing capacity,the foundation forms are mostly used as pile foundations.But the pile foundation project cost is high,its construction craft is complex,and the construction quality is not easy to guarantee.Then through the full test and study the mechanical properties of the gravel soil area,if gravel soil can meet the basic requirements of the settlement and deformation of the bearing capacity of foundation,the shallow foundation can not only reduce the project cost,but also can guarantee the quality of construction.This paper summarizes the research achievements of gravelly soil at home and abroad by analyzing the related gravelly soil.Through on-site investigation,collection and collation of geological prospecting data in this area,we fully understand the gravelly soil in this area,and thus prepare representative soil samples for large-scale direct shear tests and large indoor compression tests.The settlement of gravel soils were studied,based on the analysis Boussinesq J formula and suitable for gravel soil foundation settlement hiemer Terman method for computing foundation.In order to verify the rationality of two kinds of calculation methods for gravel soil foundation according to the load test of gravel soils results and two methods of theoretical calculation were compared,results show that the applied load is less than 400 kPa,calculate the Boussinesq criterion value greater than the actual settlement value based on the applied load;the value is less than 160 kPa hiemer,Altman method(Schmertman)value than the actual settlement value;when the applied load value from 160 kPa to 320 kPa,the calculated results are close to the measured value hiemer Terman method,can calculate the settlement of gravel soils using hiemer Terman method;in the applied load increased and is close to the capacity limit,hiemer Schmertman method the calculated value is less than the actual settlement value.These results have important engineering significance.For example,in actual geotechnical engineering,according to the size of vertical load,a more reasonable method is adopted to calculate the settlement value of the gravel foundation.Direct shear test was used to study the effects of moisture content,stone content and filler on shearing properties of slightly dense gravel soil,the test results show that with the increase of the water content,gravel soil cohesion is generally decreased,but the content change trend have distinct stages and silty clay.The change of water content has little effect on the gravel soil internal friction angle.According to the mechanical parameters of the slightly dense gravel soil,and give reasonable suggestions on bearing capacity value determination of the bearing capacity of gravel soil in the area of the specification,in order to ensure the rationality of the value of bearing capacity.Analysis shows that according to the code,the eigenvalue of subgrade bearing capacity is generally safe in this area.But when the water content is high,the width of the foundation and the depth of the soil are small,the characteristic value of the bearing capacity of the soil under the standard is larger,which means that the carrying capacity may be overestimated.The indoor compression tests of gravel soil compression curve and calculate the soil compression index,the test results show that with the increase of moisture content,compression of gravel soil increases;but the water level with the ratio of gravel soil is different for the compression performance of the influence degree,when the silty clay content in soil is high,large the particle diameter of the corresponding content of less compression performance by the influence of water content is more obvious;the proportion of aggregate in soil samples increased to reduce the compressibility of soil.Finally,in the actual project of Northeast Chongqing,through checking the bearing capacity of the foundation and calculating the settlement value of the foundation,it is considered that it is reasonable and safe to adopt the shallow foundation in the slightly crushed rock area in the northeast of Chongqing.