Experimental Study On Stress In Silt And Thermal Physical Indexes Of Compacted Silt

The silt soil is widely distributed in our country.Because of its special engineering properties,it is considered poor as filling material in the foundation and subgrade.The filling technology is often used in the road and building construction owing to the special topography and geomorphology in Shanxi area.The compaction quality of filling is the key point to ensure the safety of the superstructure.At the same time,the construction of underground transportation system becomes one of the best choice to relieve the traffic jam and the shortage of urban land.Therefore,the study of powder soil compaction characteristic,the stress characteristic in the process of compaction,and the thermal physical properties of compacted soil,not only complement the theory of compaction and thermal physical properties of geotechnical materials,but have great significance to solve practical engineering problems.The silt soil in Shanxi area was tested in this paper to analyze the compaction times,water content,compaction energy and soil thickness on soil pressure and impact force in the process of hammer,the effects of porosity,the saturation and thermal conductivity,specific heat capacity,thermal diffus ivity.The conclusions are drawn out as follows:(1)The optimal water content and the maximum dry density are slightly larger in 5 layers than those in 3 layers under the same compaction energy.(2)No matter how much the water content,the measured soil pressure increases with the increase for compaction times,and reaches the maximum value in the last of the first layer.But the impact force don,t change in the range of 2% of the optimum water content,and maintains about 12.5kN.For the second or third layer,the soil pressure and the impact force increases in the dry side of the optimum water content,but the increase is smaller than that in the first;the soil pressure and the impact force almost don't change from a hit in the wet side.With the increase of water content,the final soil pressure value and the maximum impact force of each layer increases and then decreases.With the increase of the compaction energy,the ultimate soil pressure of the first layer gradually increases;in the optimum water content and the dry side of optimum water content,the ultimate soil pressure of the second soil or third layer increases;but in the wet s ide,the ultimate soil pressure gradually decreases.In the dry side,the maximum impact force of first layer don,t change;the maximum impact force of second layer to five layer increases with the increase of compaction energy.The soil pressure decreases with the increase of compaction thickness in exponential function.(3)With the increase of porosity,the thermal conductivity and specific heat capacity decreased linearly,while the thermal diffus ivity increases gradually.With the increase of saturation,the thermal conductivity and specific heat capacity curves increases and then decreases;but the thermal diffus ivity is opposite.In addition,the thermal physical parameters have good correlation with porosity and saturation.