Rock and Soil Mechanics ›› 2019, Vol. 40 ›› Issue (7): 2825-2837.doi: 10.16285/j.rsm.2018.0497

• Geotechnical Engineering • Previous Articles     Next Articles

Determination of ultimate bearing capacity of uplift piles in combined soil and rock masses

MU Rui1, PU Shao-yun2, 3, HUANG Zhi-hong1, LI Yong-hui4, ZHENG Pei-xin5, LIU Yang1, LIU Ze6, ZHENG Hong-chao7   

  1. 1. School of Civil Engineering, Guizhou University, Guiyang, Guizhou 550025, China; 2. School of Transportation, Southeast University, Nanjing, Jiangsu 211189, China; 3. Institute of Geotechnical Engineering, Southeast University, Nanjing, Jiangsu 211189, China; 4. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, Liaoning 116024, China; 5. School of Civil Engineering and Transportation, South China University of Technology, Guangzhou, Guangdong 510641, China; 6. School of Civil Engineering, Central South University, Changsha, Hunan 410075, China; 7. Transportation Department of Miyi County, Panzhihua, Sichuan 617200, China
  • Received:2018-04-02 Online:2019-07-11 Published:2019-07-28
  • Supported by:
    This work was supported by the First-class Discipline Construction Project of Civil Engineering in Guizhou Province (QYNYL〔2017〕0013) and the National Natural Science Foundation of China (51168009).

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Abstract: In order to comprehensively explore the ultimate bearing capacity of uplift piles in combined soil and rock masses, combined with engineering geotechnical parameters and experimental data, the Flac3D numerical analysis software is adopted to carry out numerical simulation analysis to obtain the ultimate bearing capacity of uplift piles in the composite rock mass. The Kotter limit equilibrium passive equation is employed to solve the pull-out force provided by the soil layer. And based on the rock strength, the strength of the rock mass embedded in the rock pile can be determined by the Hoek-Brown failure criterion. In turn, the pull-out force of the rock mass embedded in the rock can also be obtained. In addtion, based on the principle of force balance, the ultimate bearing capacity of rock in lay uplift piles in the combined rock mass can be obtained by superimposing the pull-out resistance provided by failure rock layer and the rock mass on the gravity of failure cone. The theoretical calculation value obtained from the analytical formula is close to the numerical simulation analysis value in the case of small rock-socketed depth. However, with the increase of the rock-socketed depth, the theoretical calculation value fluctuates within a certain range around the experimental value. Therefore, combining with the numerical results, the theoretical formula of the ultimate bearing capacity is modified. Finally, by taking the consideration of the effect of rock wathering, rock-sockering depth, soil thickness and pile length, the improved ultimate bearing capacity analytical formula is obtained. The modified analytical formula is used to predict the ultimate bearing capacity of different uplift piles under different geological conditions. The predicted results show that the numerical simulation results are consistent with the theoretical calculation results, which means the analytical method of the ultimate bearing capacity of uplift piles in this paper is feasible. Based on a part of test result, the ultimate bearing capacity of different rock-socked piles with different rock-socked depths in similar projects can be determined by this method.

Key words: pile foundation engineering, uplift piles, Kotter equation, Hoek-Brown criterion, Flac3D numerical simulation, ultimate bearing capacity

CLC Number: 

  • TU 431
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