Study On Active Earth Pressure Characteristics Of EPS Particles Light Weight Soil

With the advancement of national modernization,gravity retaining walls,counterweight retaining walls and reinforced soil retaining walls have been widely used and rapidly developed.As an important indicator of retaining wall design,active earth pressure has also attracted wide attention from related scholars.As a new type of geosynthetic material,light weight soil has the advantages of light weight and high strength.It can effectively reduce the road surface settlement and the earth pressure of the retaining wall when used in roadbed engineering,which has important engineering application value.However,the research on light weight soil mainly uses indoor geotechnical test methods to explore the physical properties of light weight soil such as strength,deformation and stability,there are few reports on model tests and active earth pressure characteristics.In view of the importance of shear strength parameters for active earth pressure calculation,it is necessary to carry out related direct shear tests.In this paper,the method of combining outdoor large scale model test and indoor direct shear test is adopted.On the one hand,the earth pressure distribution law of ordinary remolded loess and light weight soil under different loading and unloading conditions and different retaining wall displacements is studied.On the other hand,based on the comparative analysis of theoretical calculation and model test,the active earth pressure calculation formula suitable for light weight soil is explored.The specific research contents and related conclusions are as follows:(1)Through the model test of using light weight soil as the backfill of the wall,it is found that the vertical earth pressure of the light weight soil during the curing period increases first and then gradually stabilizes with the increase of the curing time.After the curing time reaches 12 days,the vertical earth pressure is approximately unchanged.During the curing period,the lateral earth pressure increases approximately linearly with time.The longer the curing time,the greater the lateral earth pressure of the light weight soil,but the growth rate gradually decreases with time.In addition,it is also found that the vertical stress takes less time to reach a stable state than the lateral stress.The reading of the earth pressure cell in the fill is stable after 4 hours,while the reading of earth pressure cell on the back of the wall is stable after 12 hours.(2)Through carrying out static earth pressure model tests,it is found that the relationship between the earth pressure and the filling depth of ordinary remolded loess and light weight soil are approximately linear.The lateral earth pressure and vertical earth pressure of ordinary remolded loess and light weight soil gradually increases with the increase of the upper load.Among them,the increase range of light weight soil is smaller.Comparing the earth pressure of light weight soil with ordinary remolded loess when the retaining wall is at the state of rest,it is found that light weight soil can effectively reduce the lateral earth pressure and vertical earth pressure of the fill.The decompression effect of the lateral earth pressure is the best in the middle of the retaining wall.The decompression effect of the vertical earth pressure is the best in the lower middle of the retaining wall.(3)Through the active earth pressure model test,it is found that the displacement pattern of ordinary remolded loess is more complicated than that of light weight soil.When the displacement of ordinary remolded loess is 1mm and 2mm,the displacement mode is translational motion.Then the displacement mode is changed to rotation around the bottom of the wall,and the maximum displacement of the top of the wall is 9mm.The displacement mode of the retaining wall in the light weight soil always rotates around the bottom of the wall,and the maximum displacement of the top of the wall is 7mm,which indicates that the light weight soil can effectively reduce the lateral displacement of the retaining wall.(4)Through the active earth pressure model test,when the retaining wall moves,the relationship between lateral earth pressure and fill depth of ordinary remolded loess and light weight soil shows a parabolic distribution.The lateral earth pressure decreases first and then stabilizes as the displacement increases.For ordinary remolded loess,the stable state occurs when the displacement of the retaining wall is about 4mm.When the displacement of the retaining wall is about 3 mm,the light weight soil reaches the stable state.The active earth pressure of the ordinary remolded loess is larger than that of the light weight soil,indicating that the light weight soil can reduce the active earth pressure.(5)The lateral earth pressure coefficient is related to the displacement state of the retaining wall and the magnitude of the load.When the retaining wall is stationary,the lateral earth pressure coefficient of ordinary remolded loess fluctuates between 0.2 and 1.0as a whole,while the lateral earth pressure coefficient of light weight soil fluctuates around0.4 as a whole.When the retaining wall moves,the lateral earth pressure coefficients of ordinary remolded loess and light weight soil both decrease first and then tend to stabilize with the increase of displacement.The active earth pressure coefficient of ordinary remolded loess fluctuates around 0.04 as a whole,and the active earth pressure coefficient of light weight soil fluctuates around 0.1 as a whole,it shows that the active earth pressure coefficient of light weight soil and ordinary remolded loess is relatively stable along the wall height.(6)Calculate the active earth pressure of different fills according to the Rankine theory on the basis of the direct shear test.Compared the theoretical values with the test values,it is found that the Rankine active earth pressure of the ordinary remolded loess is relatively close to the test values,indicating that the Rankine theory has high application value in the field of ordinary remolded loess.The Rankine theory values of active earth pressure for light weight soil are all negative values.The Rankine theory values of active earth pressure for light weight soil are much smaller than the experimental values,and the crack depth obtained by Rankine theory is also very different from the experimental results,which indicates that the Rankine theory has a large deviation when applied to the field of light weight soil.(7)On the basis of the model test,the Rankine active earth pressure calculation formula is revised.After correction,the (?)abecomes K_ac/2.It is obviously different from Rankine theory that the internal friction angle no longer adopts the effective internal friction angle.Through comparison and verification,it is found that the modified formula can be applied to the active earth pressure calculation of light weight soil,which is more accurate than the Rankine theory and can provide a certain theoretical reference for practical projects.