Study On Effective Calculation Width Of Pile Foundation On Detritus Slopes

Pile foundation of transmission line in Southwest China always been built on slopping sites,so the applicability of calculation method for horizontal bearing capacity of pile foundation based on elastic semi-infinite space needs to be reconsidered.As a key index to judge the horizontal capacity of pile,calculating effective width be not only can illustrate the extent of the soil which can resist the thrust of the pile but also is an important parameter to calculate m value.Due to lateral skin friction of pile and stress diffusion phenomenon,calculating effective width will change with the change of the mechanical and geometric property of pile and site.But most current standard only take pile's geometrical conditions and pile spacing into account to rectify calculating effective width.So,in order to research calculating width in diversity aspects,we led PIV into horizontal static load test of single pile indoor on the premise of introducing diffusion angle based on full-scale pile foundation test which had been finished.According to the test results,we researched calculating effective width under 0°,15°,30° and 45° slope based on apparent fracture,soil pressure in front of pile and soil movements.After we got modified calculating effective width,we calculated m value based on modified calculating width,standard recommended calculating width and full-scale pile foundation and compared all of three.After that,we researched the effect of site slope,cohesion of soil,internal friction angle of soil,section of the pile and pile foundation embedded depth on calculating effective width and compared the result with model test.Finally,we proposed formulation of calculating effective width under diversity aspects using orthogonal test and MATLAB.There are some results we acquired:(1)Detritus slope site has obvious weakening effect on the horizontal bearing capacity of pile foundation.It is manifested in several aspects:i.Critical load and ultimate load of pile foundation will decrease with the increase of slope angle.In this model test,critical load decreases by about 1.15kN and the ultimate load decreases by about 1.10kN for every 0.2 tan?increase of site slope and the critical load is about 1.97kN and the ultimate load is about 3.25kN under the 45° slope.ii.Diffusion angle of apparent fracture of soil ?c will decrease with the increase of slop angle.In this model test,diffusion angle of apparent fracture will decreases by about 170 for every 0.2 tan? increase of site slope and diffusion angle of apparent fracture is about 19.50 under the 45°slope.?.Soil pressure in front of the pile will decrease with the increase of slope angle.In this model test,the maximum pressure of soil in front of pile will decreases by about 90kPa for every 150 increase of site slope and it is about 75kPa under the 45° slope.?.Strain areas of the soil around the laterally loaded piles which been illustrated by soil's displacement are decrease with the increase of slope angle.(2)Calculating effective width proposed by this article based on horizontal diffusional principle is less than the recommended calculating width of the standard.In this model test,calculating width under 0° slope is about be=(b+2htg46.11)m and will decrease with the increase of slope angle also.(3)We put forward a simple formulation which can calculate negative effect of the slope angle on calculating effective width.(4)We used the method recommended by?Technical Code for Building Pile Foundations?(JGJ/94-2008)to calculate m value based on rectified calculating effective width.And we found it is larger than which been calculated by recommended calculating width but it is still within the recommended reference range.(5)The modified m decreases with the increase of slope angle and we proposed a method which can calculate negative effect of slop angle on m value.(6)The cohesion of soil,friction angle of soil and slope of site have great influence on the horizontal diffusion angle of pile foundation.The sectional size of pile and the depth of pile foundation have little influence on the horizontal diffusion angle.But the sectional size of pile will affect the calculating effective width of pile foundation for geometric reasons.(7)We proposed a simple way to estimate calculating effective width under diversity aspects.