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Luo Q.-Z.,Guangdong University of Technology | Chen X.-P.,Jinan University | Wang S.,Guangdong Hydropower Planning and Design Institute | Huang J.-W.,Guangdong Hydropower Planning and Design Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2016

A series of 1D secondary consolidation tests and undrained triaxial creep tests are conducted to investigate the creep characteristics of soft dredger fill in the estuary of eastern Shantou. In 1D secondary consolidation tests, the stress-stain relationship of the soft soil shows significant nonlinear characteristics. The deformations of primary compression and secondary compression in overconsolidation state is smaller than normal consolidation case; and preloading can increase the yield strength. Pore pressure develops over time in the undrained triaxial creep tests, i. e., effective stress decreases with time. When the deviatoric stress is smaller, the deformation of soil tends to be stable, and the strain rate decreases with time; however, once the deviatoric stess reaches the critical value, the deformation develops with time rapidly, and the soil sample is damaged due to the accelerated creep. The concept of fractional order derivative is introduced to establish the fractional derivative Merchant model; and the ranges of parameters are determined. By comparison with the fitting results of traditional Merchant model, it is found that the fractional Merchant model can simulate the creep deformation better. The fractional Merchant model has a simple form and a few parameters, which can be well applied to the practical engineering. © 2016, Academia Sinica. All right reserved.

Shi Z.,Guangdong Hydropower Planning and Design Institute | Gao Z.,Jiangsu Hydraulic Engineering Construction Co.
Applied Mechanics and Materials | Year: 2011

A mathematical model for the soil-water characteristic curve is proposed in the light of bounding surface plasticity. The main drying and wetting curves are taken as the asymptotes of the scanning curves, and only one additional parameter is introduced to simulate such scanning curves. To pave to the way for the application of the proposed model, the governing equation of unsaturated seepage problems and the finite element formulations are derived. A FEM program incorporating the SWCC model is then developed and used to study the hydraulic behaviour of an earth dam undergoes a repeated change of reservoir level. Numerical results confirm the possibility and necessity of using such a hysteresis model in unsaturated seepage problems. © (2011) Trans Tech Publications, Switzerland.

Liu D.,Jinan University | Chen X.-P.,Jinan University | Chang X.-N.,Guangdong Hydropower Planning and Design Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

As the geosynthetics are widely used in engineering practice to strengthen the slope stability, the interaction behaviors of geosynthetics and soil are very important for the slope stability analysis. A reinforced seawall constructed in coast reclamation project in Guangdong Province is analyzed. The interface friction properties of reinforcing materials and filling sand are studied by means of the laboratory shear tests and theoretical analyses, and the reinforcement mechanism is discussed. The numerical calculation is carried out on the stability and deformation behaviors of the reinforced slope under geostatic pressure. The test results show that the shear stress-shear displacement relationship of geosynthetics-soil interface is strain-harding. It is important for the stability of slope in soft foudation. In addition, the density of filling sand is the key factor for the frictional characteristics of interface. The stability analysis shows that the pavement method of reinforcing materials will directly affect the factor of safety of slope stability, and multilayer pavement effect is not a simple addition for every layer. Based on the circular slip surface method, the calculated factor of safety may be too small to reflect the contribution of geosynthetics, the strength reduction method is more reasonable for considering the interface friction. The finite element analysis also reveals that the effect of reinforcement on deformation behaviors of slope is mainly in the restriction to the magnitude of lateral deformation.

Chen X.-P.,Jinan University | Zhu H.-H.,Nanjing University | Huang J.-W.,Guangdong Hydropower Planning and Design Institute | Liu D.,Shenzhen Comprehensive Geotechnical Engineering Investigation & Design Co.
Landslides | Year: 2015

In this paper, the stability of an ancient landslide during the first impounding of a nearby reservoir is investigated through the analyses of the shear strength reduction behavior of slip zone soil. In view of the experimental observations, an empirical strain-dependent soil model is established and is then incorporated in finite element analyses. The numerical analysis results show that the failing sections progressively develop due to the soil strength declines from peak toward residual, and the shear zone propagates within the front slope. It is demonstrated in the numerical results that the toe weighting measure has a significant effect on restraining the shear displacements of the soils and preventing the progressive failure of the landslide. The field observations further confirmed the stability condition of the reinforced landslide. © 2015 Springer-Verlag Berlin Heidelberg

Chen X.-P.,Jinan University | Huang J.-W.,Jinan University | Huang J.-W.,Guangdong Hydropower Planning and Design Institute | Yin S.-H.,Jinan University | Zheng J.-Z.,Jinan University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

Strength property of slip zone soils has important control action for slope stability. It is essential premise that revealing the variation law of strength indices for slope stability analysis. Aiming at an ancient landslide in reservoir area, the experimental study of shear strength of fine-grained soil containing coarse-grains in sliding zone was carried out. Based on large-scale field shear test and laboratory consolidated quick shear test, the shear characters of slip zone soils were compared; and the strength indices were defined by field recycled strength, field reduction strength, and consolidated quick shear strength in laboratory. For the deficiencies of repeated direct shear test in fine-grained soil containing coarse-grains, the improvement of test process and examination apparatus has been carried out; and the reasonability of test result was verified. Basis of the statistic rule of test data, the influence of moisture content, plasticity index, and coarse-grained content on strength indices has been discussed; the shear property distinctness between fine-grained soil containing coarse-grains and clay or sand was summarized.

Zhou H.,South China University of Technology | Cao H.,South China University of Technology | Zhang W.,Guangdong Hydropower Planning and Design Institute
Advanced Materials Research | Year: 2012

Flood-induced piping and subsequent formation of sand boils can cause severe damage to river levees. And it is known that no piping failure occurs, without seepage exit. The paper represents an experimental study on the process and mechanism of seepage exit forming on top stratum at a weak zone in a double-layer dike foundation, using sandbox modeling. According to the practical observation, three series experiments were designed. The size, thickness and the physical and mechanical properties of the top stratum are considered. The results show that the failure mode is close related to the size of the weak zone. And the hydraulic gradient of seepage exit forming is greater than the value, computed by Terzaghi's formula.

Li Z.,Hohai University | Li Z.,Guangdong Hydropower Planning and Design Institute | Hao Z.,Hohai University | Shi X.,CSIRO | And 4 more authors.
Global and Planetary Change | Year: 2016

To help the decision making process and reduce climate change impacts, hydrologically-based drought indices have been used to determine drought severity in the Tarim River Basin (TRB) over the past decades. As the major components of the surface water balance, however, the irrigation process and reservoir operations have not been incorporated into drought indices in previous studies. Therefore, efforts are needed to develop a new agricultural drought index, which is based on the Variable Infiltration Capacity (VIC) model coupled with an irrigation scheme and a reservoir module. The new drought index was derived from the simulated soil moisture data from a retrospective VIC simulation from 1961 to 2007 over the irrigated area in the TRB. The physical processes in the coupled VIC model allow the new agricultural drought index to take into account a wide range of hydrologic processes including the irrigation process and reservoir operations. Notably, the irrigation process was found to dominate the surface water balance and drought evolution in the TRB. Furthermore, the drought conditions identified by the new agricultural drought index presented a good agreement with the historical drought events that occurred in 1993-94, 2004, and 2006-07, respectively. Moreover, the spatial distribution of coupled VIC model outputs using the new drought index provided detailed information about where and to what extent droughts occurred. © 2016 Elsevier B.V.

Chen X.-P.,Jinan University | Huang J.-W.,Jinan University | Huang J.-W.,Guangdong Hydropower Planning and Design Institute | Ng C.W.W.,Hong Kong University of Science and Technology | Ma S.-K.,Guangxi University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

With regard to an ancient bank landslide near a dam, centrifugal model tests on instability mechanism under reservoir impoundment and rapid drawdown are carried out. The slope models are constructed with the consideration of large-size and heterogeneous characters of the prototype. The centrifuge tests are accompanied with real-time control of water levels, and followed by laboratorial test for physical status and strength of model slope soil. The results of centrifugal tests show that the rising water level in the reservoir leads to decreasing slope foot sliding resistance, as well as leads to edge cracks and slump. Also, the results reveal that the rapid drawdown causes slope body to produce outward hydrodynamic pressure, aggravates slope foot sliding and creates pull-typed landslide trends. When the slope foot is reinforced, the deformation is controlled and stability is improved. The soil tests of model slopes, before and after centrifuge tests, indicate that the slope foot sliding will lead to the redistribution of soil density and moisture, at the same time lead to the strength reduction near slide zone. Moreover, the cohesion of immersed soils will reduce until it vanishes finally.

Wang Y.,Nanjing University of Aeronautics and Astronautics | Wang Y.,Guangdong Hydropower Planning and Design Institute | Lu Z.,Nanjing University of Aeronautics and Astronautics | Guo T.,Nanjing University of Aeronautics and Astronautics
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics | Year: 2011

The flow field of simple terrain is described by a linearization of the flow equations. And the computational method is further simplified based on the characteristic of atmospheric boundary layer(ABL), namely, with a so-called topographic effects coefficient, the flow velocity is obtained quickly on the point (generally wind turbine's sites) being interested in. For wake effects, a modified Park model is used, which has been involved in wind farm design. The wake effects of wind turbines are linearly superimposed and the smaller ones are neglected. A typical-built seashore wind farm is introduced, including its total rated capacity, roughness of the ground and wind data measuring situation. Then as a calculating example, the power production of the wind farm is predicted by using different wind data. Most predicted values coincide well with the measured ones. Finally, it is explored why the output of each wind turbine is so different, and the conclusion presents that the size of topographic maps can influence the accuracy of wind field simulation. Also, definite suggestion about this is proposed for engineering design.

Wang X.,Sun Yat Sen University | Chiu C.-H.,Sun Yat Sen University | Guo W.,Guangdong Hydropower Planning and Design Institute
Mathematical Problems in Engineering | Year: 2014

We construct the mathematical models to find the optimal allocation of the module's capacity (module members) to different assembly operations in a module for given garment assembly tasks in a modular production system. The objectives of the models are minimizing the holding cost for work in process (WIP) inventories in the module and the total deviation of the WIP inventories from their corresponding target values in the module during a specific time interval. The solutions of the models can be used as reference to achieve better allocation of the module members to different operations in a module to fulfill the given garment assembly tasks. © 2014 Xiaoqing Wang et al.

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