The Test Research Of Pile Foundation On The Bearing Capacity In Large Thick Loess Ground

Current research on pile foundation in loess area large thickness is mainly starting from the collapsibility of loess analyses characteristics and treatment method of pile negative friction, but for the weak or non-collapsible Q2lishi loess layer research on the performance of the pile is very scarce. To determine the pile Q2Lishi loess layer thickness on the large pile in loess area for the future design of the bearing capacity of the region to provide relevant parameters, the single pile static load test was carried out.Qingyang city, Gansu province, this paper renovation projects in the circle of xifeng district south, is simulated in the large thickness of loess field static load test of pile foundation, set three test pile (800mm in diameter, pile length40m), and anchor pile eight root (800mm in diameter, pile length.18m. To eliminate the upper collapsible loess, the influence of excavation of foundation pit in advance before test, a depth of10m. Three root pile body are arranged in a large amount of reinforcement stress meter and concrete strain gauge, and symmetrical bury the earth pressure in the two groups in the pile bottom box used to test pile end load changes. Within the scope of experiment with different depths, different characteristics of pile side friction and pile top settlement process are analyzed. Will now be the result of the experiment and analysis summarized below:(1) Experimental results show that in the Middle Pleistocene silty clay (loess Q2) dominated areas of large thickness of loess, the bearing capacity of single pile is higher, and the settlement is more uniform, small settlement, can be used as a basis for load bearing structures.(2) Test pile in this paper belongs to the type of friction pile, the pile axial force not to pile end, the bearing capacity of pile endpoint0, load mainly provided by the pile side friction force. Both the axial stress of pile and pile side friction with depth distribution is not only related to the size of the pile top load, pile and soil properties, especially containing calcareous tuberculosis had a greater influence on the soil of pile side friction.(3) By test data analysis:the pile top load and deformation of pile body compression in Pt/Pu<0.80,pile top settlement is mainly caused by the elastic compression of pile; When the Pt/Pu acuity0.80, should be considered when calculating the pile settlement of the pile endpoint soil settlement Sb.(4) Under the condition of this paper, a simplified method of the comprehensive coefficient is deduced according to the specification recommended value of0.5, the calculation results of pile body compression deformation is larger, when take factor ξ=0.44, simplified method and the measured settlement of pile top is near.(5) A amount of pile body compression is used to forecast the settlement of single pile of synthetic method, this method in the loess area, the thickness of the same type of pile settlement calculation for reference.