Study On The Effect Of Soil Arching And Mechanical Behavior Of Socketed Segment On Double Row Piles

Double-row piles, as a predominant structure to resist horizontal sliding, has beenwidely used in landslide prevention, slope engineering reinforcement and other fieldsbecause of its significant advantages, such as its strong anti-sliding ability, large lateralstiffness, reasonable structure, conservation of building land and constructionconvenience, etc. Although the design concept, calculation theory and constructiontechnology of anti-sliding pile are developing continuously, in the design andconstruction of anti-slide pile, some new problems emerge because of the complexity ofgeotechnical properties. At present, it is necessary to do further research to study theformation mechanism and space form of soil arching effect of double-row piles and theinteraction of anchored segment of anti-sliding pile and rock or soil. This dissertation issupported by the program ‘Yangtze scholars and innovative research team: mountainousgeotechnical engineering(No.IRT1045)’; the project ‘Development of HealthyDiagnosis Instrument for Geotechnical Retaining Structure(No.51027004)’ of NationalNatural Science Foundation; the project ‘Plan of three-dimension soil arch effect andresearch on dynamic disaster of cantilever anti-slide piles(NO.0218002432010)’ ofHundreds of Engineering Technique Talents Project of Chongqing; the program ‘theresearch and application of key technology of pile anchor retaining structure based onthree-dimension soil arching effect(CSTC.2010AC0109)’ of Chongqing scientific andtechnological projects. The author carried out systematic studies on the formingmechanism and influential factors of soil arching effect of double-row piles, also theforce of anchored segment of piles based on wieghardt elastic foundation model byimplementing field investigation, laboratory test, numerical simulation, outdoorexperiments theoretical research and other technical methods. The main work andconclusion of this dissertation are listed as below:1) Based on the field investigation and summarize of related literature, an indoorcantilever one-row piles model test was designed to study the internal stress distributioncharacteristics of the piles and the degree and scope of arching effect of soil around thepiles. The author studied how the water percentage of landslide mass and the length ofcantilever pile affect the soil arching effect and point out that with the increasing levelof water percentage, the range of soil arching effect enhance, followed by theweakening trend. The longer the pile’s cantilever segement is, the more obvious soil arching effect is.2) Based on the indoor cantilever one-row pile model tests, an indoor double-rowpiles model test by arranging with rectangle and quincunx was designed to study theinternal force distribution pattern of front row piles and back row piles and the formingmechanism of soil arching effect. The author studied how layout of piles and pile rowdistance affect the change rule of soil arching effect with front row piles and back rowpiles and the internal force distribution pattern of front row piles and back row piles,and pointed out that the soil arching effect of cantilever double-row piles performs astrong effect on the middle and bottom of the soil, performs a weak effect performanceon the upper layer of the soil. Compared with the back row piles, the forming of soilarching effect of the front row piles has certain hysteresis. The author also finds that thedesign value of the pile row distance of double-row piles was suggested by consideringthe soil arching effect.3) Based on the indoor double-row piles model tests, an indoor embededdouble-row piles model test is also designed to compare with the cantilever double-rowpiles about the results of the stress distribution of the soil, the internal force distributionpattern and deformation of front row piles and back row piles and the formingmechanism of soil arching effect. The author found that the performance of soil archingeffect of the front row piles is weaker in the embedded double-row piles test. Theformation and destruction of soil arching effect which is analyzed on the basis ofexperimental study could be divided into four stages: local compression stage, formingstage, stable and development stage and failure stage.4) Based on the indoor double-row piles model tests, double-row piles byarranging with rectangle and quincunx have been carried on the numerical analysis byusing the finite element program ABAQUS. Same rules are acquired approximately. It isdiscussed that the influence of the internal force distribution pattern of front row pilesand back row piles and the forming mechanism of soil arching effect with changing thepile row distance, layout of piles, embedment method, plate stiffness and coupling beamwith front row piles and back row piles.5) The wieghardt elastic foundation model is introduced in this dissertation, acalculation method of ground resisting force acted on build-in zone of cantilever piles isderivated based on the wieghardt foundation model. By comparing the testing results ofcompression stress which acts on the contact surface between pile and ground with thecalculation value which are calculated with K method, trigonometric series method and the theoretical derivation method based on wieghardt foundation model, the authoranalyzes the results and points out that it is reasonable to use the method based onwieghardt elastic foundation model when the socketed segment is embedded in relativeintegrity or integrity sandstone foundation.