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Tan Y.-Z.,China Three Gorges University | Tan Y.-Z.,CAS Wuhan Institute of Rock and Soil Mechanics | Kong L.-W.,CAS Wuhan Institute of Rock and Soil Mechanics | Guo A.-G.,CAS Wuhan Institute of Rock and Soil Mechanics | Wan Z.,Hunan Communications Research Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

In order to simulate the subgrade deformation caused by the coupling effect of wetting and traffic loads, the traditional wetting deformation test method is improved, and a set of upgraded wetting-deformation equipments are developed. It is regarded that the wetting deformation is generated by the loss of matrix suction, and a constitutive relationship between lost matric suction and wetting deformation deduced. Finally, the wetting-deformation regularity and modulus are studied by using the improved device. The results show that the initial compaction state of laterite has significant effect on the deformation, and the process can be divided into three stages: initiation, acceleration and stability ones. Deformation of the specimen without wetting mainly occurs at the initiation stage, while the wetting deformation of the specimen mainly occurs at the acceleration stage.

Tan Y.-Z.,China Three Gorges University | Tan Y.-Z.,CAS Wuhan Institute of Rock and Soil Mechanics | Kong L.-W.,CAS Wuhan Institute of Rock and Soil Mechanics | Guo A.-G.,CAS Wuhan Institute of Rock and Soil Mechanics | Wan Z.,Hunan Communications Research Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

To investigate the effect of compaction on the pore size distribution characteristic of laterite soil, the compacted soil samples which were firstly subjected to pressure plate to dehydrated to their residual water content were dried by liquid nitrogen freeze-drying method; and then the corresponding pore size distribution was measured. The results show that, among samples with different dry density, the differences of characteristics of pore size distribution are obvious in the case that the pore size is larger than 10 μm. And the greater the dry density is, the fewer the pores of soil in this scope. However, most of pores of samples are mainly distributed in the range where pore size is finer than 0.1 μm and their pore distribution density are almost the same, which means that conventional compaction of soil can only change the larger pore size, no significant change for the smaller one. This also indicates that the conventional compaction has a limit effect on the compactness of the roadbed which was filled with laterite soil.

Dong C.,Central South University | Dong C.,Hunan Communications Research Institute | Leng W.-M.,Central South University | Li Z.-Y.,Hunan Communications Research Institute | Cao X.-W.,Southwest Jiaotong University
Yantu Lixue/Rock and Soil Mechanics | Year: 2013

In order to investigate the factors which affect the cement improved high liquid limit clay dynamic resilient modulus and their variation laws, a series of dynamic resilient modulus tests were carried out by conducting dynamic-triaxial tests. The study demonstrated that dynamic resilient modulus values rise with the increase of confining stress, compaction degree and cement content, decrease with the increase of circular deviator stress and moisture content. To accomplish the purpose of analysis the relationships between deviator stress, bulk stress and dynamic resilient modulus, the dual-factor analysis of variance was utilized. The analysis demonstrated that both the deviator stress and bulk stress have significant effects on the dynamic resilient modulus. However, the deviator stress has more significant effects. Considering that dynamic resilient modulus is a function of deviator stress and bulk stress, with a brief analysis of adaptability of the present dynamic resilient modulus constitutive models, the three-parameters compound constitutive model which reflects the effect of bulk stress and deviator stress was utilized for experimental data regression analysis. A high coefficient of determination shows that the model which reflects the effect of bulk stress and deviator stress is accurate and credible. The prediction models used for different compaction degrees, moisture contents and cement contents were achieved; and they can provide parameters for the pavement design based on dynamic method.

Deng L.,Hunan University | Yan W.,Hunan University | Zhu Q.,Hunan Communications Research Institute
Journal of Bridge Engineering | Year: 2016

Expansion joints will experience increasing deterioration and damage under repeating vehicle loading. A severely damaged expansion joint will induce significant dynamic vehicle load effects on the bridge deck near the expansion joint, whereas it may not cause such a large effect on the global bridge responses, e.g., deflection and bending moment at the bridge midspan. The impact factors (IMs) in bridge design codes are usually determined from global bridge responses. Therefore, it may be inappropriate to use the IMs in bridge design codes for the design of deck slabs for which the transverse bending moment is usually the controlling internal force. In this study, a three-dimensional vehicle-bridge model is used to study vehicle impact on the deck slab of prestressed concrete box-girder bridges caused by damaged expansion joints. Results show that the damage condition of expansion joints has a significant effect on the vehicle impact on the bridge deck slab, whereas it has a limited effect on the global bridge responses, especially for long bridges. The relationships between the vehicle impact on the deck slab and a few important parameters are also investigated, and some useful conclusions are obtained. © 2015 American Society of Civil Engineers.

Chen X.,Hunan University | Wu X.,Hunan University | Zou J.,Hunan University | Wan J.,Hunan Communications Research Institute
Journal of Applied Polymer Science | Year: 2012

A novel nanocomposite of the rod-like liquid crystal (LC) molecules' waist positions anchored on the surface (sidewalls and ends) of multiwall carbon nanotubes (MWNTs) was prepared by using a dissolving metal reduction method for the first time. The MWNTs carbanion complexes of lithium were first synthesized in tetrahydrofuran with an electron transfer from lithium naphthalene radical anion on the surface of MWNTs. Then the novel material (LC-MWNTs) was obtained by treating the carbanion complexes with bromic liquid crystalline aromatic amide compound. The formation of the LC-MWNTs was confirmed by both Raman and FTIR spectroscopies. HRTEM demonstrates that the rod-like LC molecules are anchored on the surface of MWNTs via covalent attachment, with a wrapped thickness approximately 3-4 nm. The loss-weight fraction of the LC layers for the LC-MWNTs can be roughly estimated as 23% by TGA. The experiments of solubility exhibit that the LC-MWNTs forms a stable suspension solution in polar solvents such as dimethylformamide. © 2011 Wiley Periodicals, Inc.

Xia C.Y.,Hunan Communications Research Institute
Applied Mechanics and Materials | Year: 2013

Influences on properties of the concrete highway pavement were analyzed in this paper, and the optimal formulation materials were gotten to use in the repair of used-broken cement blocks in the experiment. Polyurethane concrete material was prepared, combing the ordinary concrete technology with one-step method of the synthesis of polyurethane hard bubble, and then its mechanical properties of the relevant parameters were measured to determine the optimal preparation program. The results show that the polyurethane concrete also has sufficiently good mechanical properties while it has the characteristic of fast patching. © (2013) Trans Tech Publications, Switzerland.

Zhou L.-J.,Hunan Communications Research Institute
Applied Mechanics and Materials | Year: 2012

Based on limit equilibrium method, the subgrade stability formula under rainfall infiltration is derived and the influence of matric suction on subgrade stability is analyzed using the safety coefficient formula. What's more, the affection of rainfall intensity, duration and soil permeability on subgrade stability is studied and the influences is obtained. The presented research provides the theory basis to controlling of rainfall infiltration. © (2012) Trans Tech Publications, Switzerland.

Deng F.,Hunan Communications Research Institute | Li S.,Changsha University of Science and Technology
Advanced Materials Research | Year: 2013

When the recycled aggregate is crushed, many micro-cracks can be observed and some grout can remain on it. The aggregate therefore severely absorbs water when it is later mixed with concrete. The impact of water-binder ratio on strength becomes different from that of the ordinary concrete, and the ratio can no longer be used to evaluate the strength accurately. To solve this problem, this paper describes the mix proportion design method of recycled aggregate concrete, including the requirement of mix proportion design, the calculation for mixing proportion parameters and the technical requirements of recycled aggregate, natural aggregate, fly ash and admixtures. The manufacture of specimens is also described. This work provides guidance for the proper design of mix proportion of recycled aggregate concrete. © (2013) Trans Tech Publications, Switzerland.

Yang J.,Hunan Communications Research Institute
Applied Mechanics and Materials | Year: 2012

The stability of soil slope under seepage is calculated and analyzed by using finite element method based on the technique of shear strength reduction. When the condition of seepage or not is considered respectively, the critical failure state of slopes and corresponding safety coefficients can be determined by the numerical analysis and calculation. Besides, through analyzing and comparing the calculation results, it shows that seepage has a negative impact on slope stability. © (2012) Trans Tech Publications, Switzerland.

Xia C.Y.,Hunan Communications Research Institute
Applied Mechanics and Materials | Year: 2014

This paper analyzes the impact factor, combined with practical engineering experience to extract the main influencing factors, and based on research data on the major beneficial factor for statistical analysis to understand trends from the road cost; selection of multiple linear regression model, the unit cost per lane kilometer as the dependent variable, the cost factor as independent variables, the cost estimate to build the macro-factor model and the cost of each grade highway microeconomic factors estimation model. © (2014) Trans Tech Publications, Switzerland.

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