Study On Probabilistic Characteristics Of Geotechnical Parameters And Bearing Capacity Of Pile Foundation In Hangzhou Area

Soil is the engineering material strongly dependent on area. It has great spatial variability, and it also has strong uncertainness. If adopting the reliability analysis approach for geotechnical engineering, the uncertainness of various influencing factors, especially uncertainness of geotechnical parameters and calculated approach must be considered. Based on these two influencing factors, it is thoroughly studied of the probability characteristic of geotechnical parameters and the reliability of limited bearing capacity of single pile, and a set of idiographic method and approach of reliability analysis is built based much engineering data collected in Hangzhou area.Statistic analysis is done on geotechnical parameters. Collected seventy-six geological engineering information is obtained in Hangzhou area. By means of random field model of soil profile, auto-correlation distance for four typical soil Layers is computed through lateral resistance gained by static cone penetration test. Then, the associated point variability and spatial variability of geotechnical parameters are studied of some typical soil layers. Based on above results, the rule of point variability, spatial variability and distributing probability model of shear strength indexes for several soil layers is obtained, and also some variation laws of the probability characteristic of strength indexes and statistic parameters are obtained.The relations of direct shear indexes and triaxial shear indexes obtained through the experiment in the lab are quantitatively studied. Forty contrasted experiments of intensity are done. The test is done to the four typical soil layers in Hangzhou area. The shear index under the conditions of unconsolidated and undrained status, consolidated and undrained state, triaxial shear test, quick shear test. The experiential relations of material index arc obtained through correlation discrepancy analysis.The reliability about two type of pile foundation commonly used is studies. Sixty-four tested pile data in twenty-eight engineering fields of Hangzhou area obtained, and the types of pile include bored pile and prefabricated pile. Based on the statistic and analysis, the ultimate bearing capacity of piles is computed and the variance laws ofultimate bearing capacity between calculated and testing value are studied for failure state and far from failure state using different methods. The uncertainty of the two types of piles is studied to the mode of single pile under the ultimate bearing capacity conditions. The computed mode on the ultimate bearing capacity calculation of piles is obtained suiting for Hangzhou area.Due to having more layers of soil between the piles, there are many variables in the probability ultimate limit state design. It is put forward of an approach of dealing with stochastic variables and translating multi-variables into single variable to analysis considering the effect of correlative distance on variability. Therefore, the reliability based on JC is computed to the bored and prefabricated piles under the conditions of different load reactions ratios, load combination. The index in different instances is obtained under different conditions by statistic analysis of the various effect factors.The coefficient of subentry between lateral resistance and end resistance of piles in different instance is calculated using the complete reliability analysis approach and the variation laws of the partial factors.