Dynamic index evaluation method for subgrade bearing capacity controlled by PFWD modulus
Li Danfeng1,2 Yang Guangqing1,2 Liu Weichao1,2
1. State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures, Shijiazhuang Tiedao University, Shijiazhuang 050043, China；
2. School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
Abstract：Giving the current situation that it is difficult to form a unified standard for the dynamic determination of subgrade bearing capacity and the deflection control indexes can not be tested measured, a dynamic mechanical index evaluation method for subgrade bearing capacity based on Portable Falling Weight Deflectometer (PFWD) modulus control is proposed. Based on the physical model of the elastic half space under impact load, the difference of dynamic and static mechanical indexes of PFWD is analyzed theoretically, and the spatial distribution of dynamic stress of elastic subgrade soil under impact load is analyzed by the finite element numerical simulation method. The combined detection method of PFWD and BB is used to evaluate the subgrade bearing capacity of supporting projects, reveal the detection characteristics of PFWD, and propose the accurate measurement method Law. The research results show that the influence range of PFWD is 2.5 times the diameter of bearing plate in the depth direction and 2 times the diameter of bearing plate in the horizontal direction. The attenuation rule of dynamic stress of elastic subgrade soil under impact load is that the attenuation direction of σz is the same as that of depth, and the attenuation direction of σr is 45° with faster attenuation speed. The fundamental reasons for the error in dynamic and static mechanical test indexes are the non-linear elastic characteristics and the incomplete contact between the rigid bearing plate and the subgrade soil and. The detection characteristic of PFWD is the overestimation of subgrade stiffness. The greater the stiffness is, the smaller the dynamic and static difference is. A dynamic prediction model with high correlation coefficient is proposed, thus the correction of the linear model to the origin is avoided, and high-precision detection is achived. A rapid detection method and idea based on the modulus control is established, which can provide reference for the dynamic accurate measurement and scientific evaluation ofsubgrade bearing capacity of expressway.
李丹枫 杨广庆 刘伟超. PFWD模量控制的路基承载力动力学指标评价方法[J]. 土木工程学报, 2021, 54(6): 117-128.
Li Danfeng Yang Guangqing Liu Weichao. Dynamic index evaluation method for subgrade bearing capacity controlled by PFWD modulus. 土木工程学报, 2021, 54(6): 117-128.
