Response Of Erosion Resistance Of Compacted Soil To Dry-wet Alternation

As a kind of farmland,terraced field is an important measure to control soil and water loss in sloping farmland.Distribution in our country has a large area of farmland,mainly distributed in the Midwest,terrance engineering implementation of large areas of farmland were transformed into terraces,to increase the high grade agricultural land area,improving the standard of living of local residents is of great significance,the ridge terrace is a terrace of terrace type is larger type.In the natural state,due to the influence of terrain,climate,soil and the natural action in the use process,the slope collapse occurs in the terraces of Tukan.The quality of the slope directly affects the water storage and soil conservation efficiency of the terraces.Therefore,the research on the protection of the terraces of Tukan becomes particularly important.In this paper,by simulating the process of dry-wet alternation under natural conditions,the shear strength,critical shear force,soil disintegration speed,soil scouring resistance,soil permeability coefficient and other indexes under the action of dry-wet alternation are measured,and the comprehensive erosion resistance index is calculated by the weighted synthesis method of the above indexes.Based on the comprehensive erosion resistance index analysis of the effect of dry-wetting alternation on soil erosion resistance,the collapse mechanism of soil terraces was revealed.The main results are as follows: The test results of shear strength under dry-wetting alternation showed that the soil cohesion increased from 2.25 kPa to 5.40 kPa with the increase of dry-wetting alternation times.The soil internal friction Angle decreased from 5.65° to 4.28°.With the increase of dry-wet alternating frequency,the shear strength of soil does not change significantly under the vertical pressure of 100 kPa.Under the vertical pressure of 200 kPa,the shear strength of soil first increases and then gradually becomes stable.Under the vertical pressure of 300 kPa and 400 kPa,the shear strength of soil increases first and then decreases,and finally becomes stable.The significance analysis showed that the effect of different wetting and drying treatments on the internal friction Angle was greater than the cohesion.The results of soil critical shear force test show that 1～3 times of dry-wetting alternation have no significant effect on the critical shear force,and the value fluctuates between 0.19 kPa and 0.41 kPa.After 4-7 times of dry-wetting alternation,the critical shear force increased slightly and tended to be stable,and the value increased from 0.41 kPa to 0.90 kPa.Permeability coefficient increased with the increase of dry-wet alternation times.The results of soil disintegration test showed that the disintegration rate decreased from2.48 g/s to 0.38 g/s,indicating that the dry-wet alternation had a weakening effect on the soil disintegration rate.With the increase of dry-wet alternation frequency,the disintegration process(three stages)was gradually delayed.The results of soil anti-impact test show that: The anti-scouring coefficient began to decrease after increasing from 0.22 L/g to 0.40 L/g,indicating that the dry-wetting alternation had a certain strengthening effect on the anti-scouring ability of soil.With the increase of the number of dry-wetting alternation,the anti-scouring ability of soil first increased and then decreased.The indexes obtained from the above tests were taken as the factors to judge the anti-erosion ability of soil.The change of soil erosion resistance was obtained by calculating the comprehensive soil erosion resistance index.The results show that the internal friction Angle and cohesion have the most sensitive effects on soil erosion resistance index,the permeability coefficient,critical shear force and impact coefficient have relatively weak effects,and the disintegration rate has the least effect.Under the premise of a limited number of times(0～7),the soil erosion resistance increased to a certain extent with the increase of dry-wet alternating times(n).The soil erosion resistance decreased after reaching the maximum value for 5 times,and gradually stabilized after 6 times.In conclusion,on the premise of limited number of dry-wetting alternations,soil erosion resistance can be enhanced to a certain extent,mainly through internal friction Angle and cohesion,but this enhancement is limited,and soil erosion resistance begins to decline with the increase of dry-wetting alternations.