Research On The Analysis Of The Collapse Influence Factors And Stability Evaluation Of The Hole-wall Of Large Aperture Bored Piles

There are a lot of soft soil foundation In southeast coastal areas of China, thebearing capacity of the foundation is low and the deformation is bigger, this kind offoundation often cannot meet the requirements of upper structure diverse buildingdevelopment, the emergence and development of the bored piles solve the problem ofthe bearing capacity of soft soil foundation. Bored piles have many advantages, such asnon vibration during construction, lower noise, and adaptable to the construction ofbuildings in the city populated areas etc. Therefore, bored piles are widely used inmodern engineering construction, but many problems still exist in the process of theconstruction of bored piles, the stability problem of the hole-wall is particularlyprominent. The stability problem of the hole-wall affect the construction progress,increase the construction cost, reduce the bearing capacity of pile foundation, seriouslyrestricts the development and application of bored piles.In this paper, on the basis of previous studies, starting with the constructiontechnology of bored piles, analyses the stability problem of the hole-wall during theconstruction process. Combine with the characteristics of petrochemical engineeringproject in Guangdong China, the stability of hole-wall mechanics analysis andevaluation model is established; systematically expounds the factors that influence thestability of hole-wall of the bored piles and using the basic principles of quantificationtheory to build the evaluation model of the stability of the hole-wall. Basing on theseresearching results, using the finite element software ABAQUS to simulating analysisand evaluation the stability of hole-wall about part of the influence factors, and putforward the corresponding measures to guide the construction according to the result ofthe simulation, provide a theoretical basis for prevent and control the hole-wallcollapsing of bored piles engineering of Guangdong petrochemical projects(1) Systematically analysis and summary the drilling techniques of bored piles,aiming at the stability problem of the hole-wall of specific bored piles engineering ofpetrochemical project in Guangdong, researching and determining the exact factors thatcauses the hole collapse, research and determine the specific causes of the hole collapse. (2) On the basis of systematically analysis the soil conditions of the foundation, themechanical evaluation model of the stability of bore piles hole-wall were established,context of the specific engineering projects. And then determine the stress calculationformula of soil around the hole-wall, and determine the stability condition of thehole-wall during the construction process of bored piles by yield criterions of elasticmechanics and plastic mechanics.(3) According to the pile-hole collapse characteristics and distribution of typicalcoastal areas of Guangdong petrochemical bored pile foundation engineeringconstruction, research and determine pile-hole wall stability evaluation parameters;Each borehole drilling hole wall and the collapse of the soil volume is defined as thefilling pile porosity collapse of hole wall, and on the basis of the relation between theinfluence factors: pile-hole collapse rate and stratum structure, soil properties, thicknessand drilling depth and drilling construction methods, using the basic principle ofquantification theory to establish the influence factors of hole-wall stability theory ofquantification evaluation model; quantitative analysis and evaluation of the existingpiles hole collapse factors and stability of the quantitative relationship through thetheory of the hole collapse factors of quantification evaluation model.(4) Using the large finite element software ABAQUS to make a series ofsimulation experiment and study about the relationship between the impact factors andthe lateral deformation of drilling hole-wall, impact factors such as mud weight, thehole diameter, hole depth, and groundwater activity are included, studying andanalyzing the drilling hole-wall stability changing rule under different influence factors.