The Sturdy Of Rigid Pile’s Degree Of Reliability In Chengdao

Due to the particularity and complexity of geotechnical engineering and pile foundation,the application of reliability design theory is not yet mature, and because of the late oflarge-scale construction projects start, backwardness of technological and lag of practice, theregional theoretical research in the Chengdao region develops slowly. The reliability of pilefoundation has strong regional feature, which inseparable with local soil properties. Thekeys and difficult points of piles’ reliability analysis are the uncertainty of soil parameters andhow to establish the probabilistic model and description of soil profile in geotechnicalengineering reliability analysis. Rigid piles, as the most widely used type of pile foundation insoft ground of coastal and delta region, its transfer mechanism of the bearing capacity, thedeformation-settlement are closely related to the soil, while the soft soil in the region has itsown unique projects nature, which has a significant impact on reliability of the pile.Soft soil is widely distributed in the Chengdao region, its engineering properties areshown as: high moisture capacity, low strength, large compressibility and low permeabilitycharacteristics. Nevertheless, theoretical study is also far from enough to meet the needs ofpractice. Based on systematic and comprehensive investigation and necessary field test in theregion, the parameters of physical and mechanical properties are studied and detailedstatistical analysis by modern mathematical statistical analysis; and correlation equation ofparameters, and the regional mechanical model of soft soil are obtained. The results can beused as reference to test indexes, and can solve some practical problems, such as the complexand blind test process, long cycle and big error in test.According to the data of property parameter from laboratory geotechnical test of soilobtained in field investigation, the bearing capacity of a single pile, effect factors andcorrelation are carried on systematic research, which take drilled grouting pile and Dry JetMixing(DJM) pile instance between soil and pile from both theoretical and experimental. Themain factors which influence the reliability slip of pile-soil can be expressed as follows: theload of the pile head, the density of the pile body, the cohesive and friction factor between pileand soil. And the main factors which influence the reliability friction of pile side can also beexpressed as follows: the load of the pile head, the internal angle of soil, the density of thepile body, the friction factor between pile and soil and the density of soil. The main factorswhich influence the reliability of pile end bearing are cohesive and friction factor betweenpile and soil. The models of pile-soil and reliability are established in the area, which can beused for the base of pile foundation design evaluation, to guide the practice of engineering, and solve the problem of complex pile testing process, long cycle, high cost, less sample andpoor representation.Based on bearing performance of the DJM pile composite foundation which is studied byway of static load tests, pile-soil stress ratio tests, in the start of the pile load tests and strengthof cement-soil indoor study, we determined the important design parameters of the capacity ofDJM pile composite foundation and pile-soil stress ratio, and did systematic investigation ontime effect of bearing capacity of a single DJM pile. The trends of pile-soil stress ratio areobtained by the theory of data analysis, which mainly distributed about6.4to9.2.Working mechanism of pile foundation is analyzed by way of field static load tests. Majorfactors which effect indicator of pile foundation degree of reliability is analyzed by numericalsimulation of Montle-carlo method, which combined with the finite element method andreliability design theory. Compare and analyze the curves of the numerical simulation andsettlement with the curves which obtained by on-site load test curves, single pile reliabilitywas studied under the parameters of appropriate adjustment and inversion analysis.According to vertical loading test of pile data, the "pile group effect" and the reliability of pilegroups were studied.Based on the sensitivity of design variables for objective function, optimization of theDJM pile composite foundation is studied by the way of first-order method. At the premise ofsatisfying the demands of strength and deformation, taking the cement consumption as theobjective function, influences of design variables on bearing capacity and deformation areanalyzed. Optimization combination of pile length, replacement ratio and cement ratio can becalculated, which can be suitable for ground improvement in Chengdao region.