Finite Element Analysis On Bearing Capacity Of Group Piles In Permafrost Regions

Permafrost is widely distributed in the northeastern region of China and the Qinghai-Tibet Plateau region.The long-term load-bearing properties of the building foundation in permafrost regions ensure the safety of building construction and use.The types of permafrost in China are complex.Permafrost temperature,geological conditions and other factors affect the bearing capacity of the building foundation.The pile foundation has the advantages of large bearing capacity,wide applicability,simple construction,less disturbance to ground temperature.So the pile foundation is the most common foundation of permafrost.However,due to the complexity of permafrost and the diversification of the regional division,the study of the pile foundation,especially the group pile in the permafrost region is not perfect as in the ordinary soil.And the group pile can not carry out the load test in the frozen area.And the indoor model test is difficult to simulate the complex working state of pile groups in permafrost.So it is very meaningful to carry out numerical simulation analysis.This paper reviews some of the previous studies on the pile foundation of the cold area as well as the basic working principle of pile group under vertical load.And then introduced a large finite element analysis software Midas / GTS.The finite element model,the calculation unit,the contact element and the constitutive model of numerical simulation are introduced.And the 3D visualization model was used to simulate the bearing behavior of pile foundation in permafrost region.By comparing the results of the single pile load test in the frozen soil area and the numerical simulation results.We determined the accuracy of the parameters and the accuracy of this finite element software for the analysis of permafrost.Then,we carried out the finite element analysis of single pile and pile group.In this paper,the permafrost parameters of three different temperatures were selected.A single pile model with different pile diameter of 10 m pile length was fabricated.And 2 × 2 group piles and plum piles models with pile length of 15 m and 1m diameter were fabricated.The influence of soil temperature and pile diameter on bearing capacity of pile and the influence of pile number and pile distance on pile foundation are studied.The settlement,axial force,pile bottom force and freezing force of pile foundation are analyzed.The pile group effect,damage characteristics,damage mode were studied.It is concluded that increasing the pile diameter and decreasing the permafrost temperature can significantly improve the bearing capacity.The increase of the distance of pile in a certain range can reduce the settlement of pile group and increase the bearing capacity of pile group.Does not change the pile spacing and increase the number of piles will not significantly improve the carrying capacity but will increase the settlement.It is proved that it is possible to analyze the working condition of pile foundation in frozen soil by finite element analysis software Midas/GTS.