摘要：
The resilient modulus has been used to characterise the stress-strain non-linear behaviour of subgrade soils and is an important parameter for pavement design and analysis. This study aims at developing an accurate and efficient methodology to estimate the resilient modulus of subgrade soils. Therefore, repeated load triaxial tests were carried out in this study. The soil matric suction was measured by the pressure plate test and the soil-water characteristic curve (SWCC) was described using the Fredlund & Xing model. Then, the influence of stress state, matric suction and relative compaction on the resilient modulus were analysed. Subsequently, a new resilient modulus model was proposed to incorporate the relative compaction and matric suction in addition to the stress state. The new model matched 7 sets of experimental data well and the coefficients of determination were high, which indicates that this new model is reasonable and widely applicable. Finally, the correlations between the basic properties variables of soil samples and the regression coefficients of the new model were established.
关键词：
Pile-soil interaction;Poroelastic medium;Two-dimensional rod;Radial deformation;Boer's poroelastic model
摘要：
The paper presents an analytical solution for the vertical dynamic interaction analysis of a poroelastic soil layer and an embedded pile with the consideration of pile-soil radial deformations. The soil is treated a three-dimensional porous continuum and described by the Boer's poroelastic model, while the pile is treated as a two-dimensional rod with both radial and vertical deformations of which the equation of motion is derived by the Hamilton's variational principle. Without the introduction of potential functions, first take the volumetric strain of soil skeleton and pore fluid pressure as intermediate variables to deal with the equations of motion for the soil and then use the separation of variables to solve the equations of motion for the soil and the pile. By imposing the boundary and continuity conditions of the pile-soil system, the dynamic impedance in frequency domain and the velocity response in time domain of the pile top are obtained. The present solution is then verified by comparing with the corresponding finite element model computation results and the existing solutions. The effects of the pile-soil parameters on the dynamic characteristic of the pile-soil system are also analyzed. Some significant conclusions are drawn, which can provide useful reference for related engineering practice. (C) 2020 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
摘要：
This study aims at developing an efficient and accurate methodology to estimate the resilient modulus of subgrade soils. First, a new resilient modulus model incorporating stress dependence and moisture dependence was proposed. Second, prediction models were developed to conveniently and accurately determine model parameters of SWCC and resilient modulus model. In order to characterise the moisture dependence of subgrade soils, the matric suction was added into the proposed model. The matric suction was measured by the pressure plate test and the soil-water characteristic curve (SWCC) was used to determine the matric suction value at any given moisture contents. In order to develop prediction models for model parameters of SWCC and resilient modulus model, the laboratory experiments and multiple regression analysis were conducted on 22 soil samples. A series of performance-related soil properties were measured and used to develop the coefficients prediction models. The developed coefficients prediction models using the performance-related soil properties have high R-squared values and were validated by comparing the measured and predicted values of resilient modulus. Therefore, when the basic physical properties of soils were obtained, the resilient modulus can be predicted for the subgrade soils at any given matric suctions and stress states.
作者机构：
[徐方; 顾功辉] Faculty of Engineering, China University of Geosciences, Wuhan, 430074, China;[黄晓明] School of Transportation, Southeast University, Nanjing, 211189, China;[张军辉] National Engineering Laboratory of Highway Maintenance Technology, Changsha University of Science & Technology, Changsha, 410114, China;[朱婧] Hubei Communications Technical College, Wuhan, 430079, China
关键词：
humid and hot areas;existing subgrade;deterioration mechanism;rapid detection;portable falling weight deflectometer;dynamic cone penetrometer
摘要：
To relieve the increasing traffic load, many early built highways need to be widened or reconstructed. The rapid performance detection to existing subgrades is important to their reasonable evaluation and maximized utilization. Based on five kinds of soils taken from an existing highway in southern China, three commonly detecting methods were used to determine their moisture contents, compaction degrees and resilient moduli. The results showed that the measured moisture contents were greater than the design value, and the compaction degrees decreased sharply compared to the original ones. The moisture and heat exchange produced a decrease in the resilient modulus of plate loading test (PLT) from the standard 60 MPa down to 40 MPa. Afterwards, the portable falling weight deflectometer (PFWD) and dynamic cone penetrometer (DCP) were used to evaluate the subgrade performances. The measured PFWD moduli and the DCP penetration rates were correlated with the resilient moduli of PLT, deflections of the Beckman beam test, compaction degrees and moisture contents. The correlation analysis indicates that both of two methods are suitable in rapid detecting subgrade performances, but PFWD method is more recommended for it has higher accuracy and efficiency.
通讯机构：
Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, China
期刊：
Transportation Safety and Environment,2020年2(1):18-28 ISSN：2631-6765
通讯作者：
Zeng, Ling(zl001@csust.edu.cn)
作者机构：
[Junhui Zhang; Le Ding] National Engineering Laboratory of Highway Maintenance Technology, Changsha University of Science and Technology, Changsha Hunan, China;[Ling Zeng] School of Civil Engineering, Changsha University of Science and Technology, Changsha Hunan, China;[Qianfeng Gao] School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha Hunan, China;National Center for Asphalt Technology, Auburn University, 277 Technology Parkway, Auburn;AL
通讯机构：
[Ling Zeng] S;School of Civil Engineering, Changsha University of Science & Technology , Changsha Hunan, China
摘要：
The use of waste tire rubber as asphalt modifier has been a practice-ready technology. However, the interaction among components within asphalt rubber (AR) and warm asphalt rubber (WAR) is still unclear. During the blending process, the swelling rubber releases polymer agents in asphalt and absorbs components from both asphalt and warm mix asphalt (WMA) additive simultaneously. The component interaction significantly influences the final rheological properties. A comprehensive understanding of the selective absorption of crumb rubber during the blending process provides references to optimize the material and procedure design of rubberized asphalt. To this end, one AR and two WARs were prepared with three mixing durations. The liquid phases and crumb rubber particles were separated. The separated swelling rubber particles were then processed by the staged extraction method to divide the asphalt-rubber interacting area from outside to inside into four layers. The absorption preference of swelling rubber and its influence on rheological properties were investigated by chemical and rheological tests. Test results showed that asphalt fractions with smaller molecular weight were absorbed into deeper layers of swelling rubber. By contrast, crumb rubber was found to be reluctant to absorb the fractions with CAO bond during the mixing process. In addition, the Fischer Tropsch (FT) wax showed a negligible influence on the absorption preference, while the effect of surfactant on absorption preference was significant. Finally, the relationship between absorption preference and rheological properties was established. It was found that the absorption preference of crumb rubber is beneficial to the rutting resistance of rubberized asphalt. (C) 2019 Elsevier Ltd. All rights reserved.
关键词：
Nano-CaCO3;Pre-Disintegrated Carbonaceous Mudstone;Cyclic Wetting and Drying;Final Crack Rate;Evolution
摘要：
To explore the evolution of cracks in the pre-disintegrated carbonaceous mudstone, wetting-drying tests were carried out on nano-CaCO3 modified pre-disintegrated carbonaceous mudstone samples. The samples were prepared with aqueous solutions of different pH values. Scanning electron microscopy (SEM) was performed to clarify the mechanism of crack evolution of pre-disintegrated carbonaceous mudstone modified by nano-CaCO3. The results showed that development of shrinkage and cracks was basically divided into three stages, i.e., the gestation stage, the rapid development stage and the stable stage. For the samples without nano-CaCO3, the final crack rates and pore sizes of samples with pH = 3 and pH = 11 were larger than corresponding values of the sample with pH = 7. Moreover, final crack rate and pore size significantly decreased with the addition of nano-CaCO3 suggesting that nano-CaCO3 can effectively improve cracking resistance of pre-disintegrated carbonaceous mudstone.
摘要：
To achieve durability of the embankment in southern China, a method to control the change of moisture content with the cushion and cover was proposed. A finite element model of cushion and cover considering different materials and thicknesses for a typical embankment was built, and 20 numerical analyses of transient seepage in the embankment were simulated. The results show that the sand cushion effectively blocks the effect of groundwater capillary rise and the minimum thickness of the sand cushion is 75 cm without considering the atmospheric environment. With the combination of sand cushion and clay cover, as the thickness of the clay cover increases, the duration time of the moisture content from the initial to relative equilibrium state increases, but the equilibrium moisture content is the same as that of the original embankment. Besides, with the combination of the sand cushion and sand cover, the moisture content inside the embankment remains the same, which is consistent with the optimum moisture content during construction. The combination of 75 cm sand cushion and 30 cm sand cover is a very effective method to block groundwater and atmospheric environment, and achieve the control of the humidity stability of the embankment in southern China.
