Research On Characteristics Of Soil Arch Effect Behind Piles Based On Transparent Soil Technology

Landslide is a serious natural disaster second only to earthquakes and floods.In western China,the terrain is mostly mountainous.Especially in the rainy season,landslides are characterized by high density and high frequency.Therefore,China is also one of the countries most seriously affected by landslides in the world.Most of the western regions are mountainous areas,and the rainy season is concentrated.Therefore,China is also one of the countries most seriously affected by landslides.Landslides cause huge losses to national life and property safety every year.In order to protect people's lives and property safety,more in-depth research and analysis of landslides and their management are needed.Anti-slide piles are an important engineering measure in slope management.In the study of pile-soil interaction,soil arching effect and it is an important part.The predecessors have conducted in-depth studies on soil arching effects using model tests and numerical simulations.However,due to the influence of traditional model test interventional measurements,there is no unified understanding of soil arching effects.With the development of science and technology,the use of synthetic transparent soil and PIV technology has made it possible to visualize the effect of soil arching.In this paper,a set of test equipment consisting of thrust system,slope simulation system,anti-slide pile system,speckle system,and information acquisition and processing system is designed based on the transparent soil technology and the formation conditions of the soil arch.The device is used to obtain the image formed by the laser speckle field during the sliding process,and then the particle image velocimetry(PIV)technology is used to analyze the displacement characteristics of the speckle field,and then the soil arch effect of the round pile is analyzed The following results were obtained through model tests:(1)The transparent clay used in this article is composed of fused silica sand mixed with n-dodecane and No.15 white oil.Through multiple test comparisons,it is found at 20?,the volume ratio of n-dodecane to No.15 white oil is 1:2.5,and the refractive index is 1.4585,the transparency of transparent clay is the best.It is concluded that the refractive index n of the mixed liquid at a certain temperature is related to the refractive index m and volume of n-dodecane n1 and No.15 white oil at that temperature,and is satisfied n=n1V1+n2V2/V1+V2 Compared with the physical and mechanical properties of transparent soil,it is found that the transparent soil prepared in this paper is similar to the fine silt in nature.(2)The particle image velocimetry(PIV)technology is used to analyze the test image.In the displacement cloud diagram,an arch structure composed of equal displacement lines is observed,and it is divided into four different regions according to the different characteristics of the region.Areas ? and ? are soil arch effect areas,which are found to be roughly parabolic.Combined with the structure of the round pile in the test,by comparing the test results of different depths,it is concluded that the single-row round pile shows the most developed soil arch effect at the bottom end and the highest arch height due to the deflection of the top force;the top soil arch effect lags and the arch height The smallest,the soil arch height gradually decreases from the bottom of the round pile to the top.(3)Through the analysis of the arch line characteristics of the soil arch behind the piles,it is proposed that the factors affecting their characteristics are pile diameter,pile spacing and depth.Moreover,with the increase of the displacement of the model box,the height of the soil arches behind the piles is gradually increased first,and finally tends to a stable value.The maximum arch height H of the soil arch behind the pile satisfies H-?d(n+1)-0.375?S the pile diameter d,the distance ratio L/d,and the depth S.Through theoretical derivation and correction of transparent soil test results,it is found that the soil arch between the piles is not only related to the pile diameter d and pile spacing L,but also to the nature of the soil body,and its maximum arch height H'=1/4?(L-D)tan ?+1/2?d.(4)The experimental device was used to study the evolution of the shape of the soil arch in the depth direction,and it was found that with the increase of the sliding displacement,the maximum arch height of the soil arch at different depths showed the characteristics of increasing first and then tending to stability(5)For single-row piles,using ABAQUS to simulate different pile diameters,pile spacing and other working conditions,it can be seen from the displacement contour map that the shape of the soil arch is basically parabolic;as the landslide thrust gradually increases,The larger the pile diameter and the smaller the pile spacing,the stronger the "wedge tightening" effect between the soil particles,which is more beneficial to the full play of the soil arch effect;and when the landslide thrust increases to a certain level,it reaches the soil The bearing limit of the arch,the formed soil arch can not bear the pressure of the soil behind the pile,the "wedge tightening" effect between the soil particles fails,and the soil arch is destroyed and disappears.And using ABAQUS to simulate and analyze the soil arch effect of the double-row piles with different layouts and different row spacings,it is found that the overall soil arches formed by the "rectangular" and "plum blossom" layouts are consistent,but from In terms of stability,the "plum blossom" arrangement is slightly better than the "rectangular" arrangement.For different row spacings,the soil arching effect of the front row piles is basically the same as that of the single row piles,while the height of the soil arching of the rear row piles increases with the row spacing,showing the characteristic that it increases first and then remains basically unchanged.