Affected by typhoons over years, Fujian Province in Southeast China has developed a large number of shallow landslides, causing a long-term concern for the local government. The study on shallow landslide is not only ...Affected by typhoons over years, Fujian Province in Southeast China has developed a large number of shallow landslides, causing a long-term concern for the local government. The study on shallow landslide is not only helpful to the local government in disaster prevention, but also the theoretical basis of regional early warning technology. To determine the whole-process characteristics and failure mechanisms of flow-slide failure of granite residual soil slopes, we conducted a detailed hazard investigation in Minqing County, Fujian Province, which was impacted by Typhoon Lupit-induced heavy rainfall in August 2021. Based on the investigation and preliminary analysis results, we conducted indoor artificial rainfall physical model tests and obtained the whole-process characteristics of flow-slide failure of granite residual soil landslides. Under the action of heavy rainfall, a granite residual soil slope experiences initial deformation at the slope toe and exhibits development characteristics of continuous traction deformation toward the middle and upper parts of the slope. The critical volumetric water content during slope failure is approximately 53%. Granite residual soil is in a state of high volumetric water content under heavy rainfall conditions, and the shear strength decreases, resulting in a decrease in stability and finally failure occurrence. The new free face generated after failure constitutes an adverse condition for continued traction deformation and failure. As the soil permeability(cm/h) is less than the rainfall intensity(mm/h), and it is difficult for rainwater to continuously infiltrate in short-term rainfall, the influence depth of heavy rainfall is limited. The load of loose deposits at the slope foot also limits the development of deep deformation and failure. With the continuous effect of heavy rainfall, the surface runoff increases gradually, and the influence mode changes from instability failure caused by rainfall infiltration to erosion and scouring of surface runoff on slope surface. Transportation of loose materials by surface runoff is an important reason for prominent siltation in disaster-prone areas.展开更多
A constitutive model on the evolution of debris flow with and without a barrier was established based on the theory of the Bingham model. A certain area of the Laoshan Mountain in Nanjing, Jiangsu Province, in China w...A constitutive model on the evolution of debris flow with and without a barrier was established based on the theory of the Bingham model. A certain area of the Laoshan Mountain in Nanjing, Jiangsu Province, in China was chosen for experimental study, and the slope sliding and debris flow detection system was utilized. The change curve of the soil moisture content was attained, demonstrating that the moisture content of the shallow soil layer increases faster than that of the deep soil layer, and that the growth rate of the soil moisture content of the steep slope is large under the first weak rainfall, and that of the gentle slope is significantly affected by the second heavy rainfall. For the steep slope, slope sliding first occurs on the upper slope surface under heavy rainfall and further develops along the top platform and lower slope surface, while under weak rainfall the soil moisture content at the lower part of the slope first increases because of the high runoff velocity, meaning that failure occurring there is more serious. When a barrier was placed at a high position on a slope, debris flow was separated and distributed early and had less ability to carry solids, and the variation of the greatest depth of erosion pits on soil slopes was not significant.展开更多
The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment,which realizes the multi-motion modes of the autonomous underwater vehicle(AUV) such as vectored thruster and wheeled mo...The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment,which realizes the multi-motion modes of the autonomous underwater vehicle(AUV) such as vectored thruster and wheeled movement.In order to study the interactional principle between the hull and the wheel propellers while the AUV navigating in water,the computational fluid dynamics(CFD) method is used to simulate numerically the unsteady viscous flow around AUV with propellers by using the Reynolds-averaged Navier-Stokes(RANS) equations,shear-stress transport(SST) k-w model and pressure with splitting of operators(PISO) algorithm based on sliding mesh.The hydrodynamic parameters of AUV with propellers such as resistance,pressure and velocity are got,which reflect well the real ambient flow field of AUV with propellers.Then,the semi-implicit method for pressure-linked equations(SIMPLE) algorithm is used to compute the steady viscous flow field of AUV hull and propellers,respectively.The computational results agree well with the experimental data,which shows that the numerical method has good accuracy in the prediction of hydrodynamic performance.The interaction between AUV hull and wheel propellers is predicted qualitatively and quantitatively by comparing the hydrodynamic parameters such as resistance,pressure and velocity with those from integral computation and partial computation of the viscous flow around AUV with propellers,which provides an effective reference to the study on noise and vibration of AUV hull and propellers in real environment.It also provides technical support for the design of new AUVs.展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.U2005205,41977252)National Key R&D Program of China(2018YFC1505503)+1 种基金Open Fund of Key Laboratory of Geohazard Prevention of Hilly Mountains,Ministry of Natural Resources(Fujian Key Laboratory of Geohazard Prevention)(FJKLGH2022K001)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2020Z001)。
文摘Affected by typhoons over years, Fujian Province in Southeast China has developed a large number of shallow landslides, causing a long-term concern for the local government. The study on shallow landslide is not only helpful to the local government in disaster prevention, but also the theoretical basis of regional early warning technology. To determine the whole-process characteristics and failure mechanisms of flow-slide failure of granite residual soil slopes, we conducted a detailed hazard investigation in Minqing County, Fujian Province, which was impacted by Typhoon Lupit-induced heavy rainfall in August 2021. Based on the investigation and preliminary analysis results, we conducted indoor artificial rainfall physical model tests and obtained the whole-process characteristics of flow-slide failure of granite residual soil landslides. Under the action of heavy rainfall, a granite residual soil slope experiences initial deformation at the slope toe and exhibits development characteristics of continuous traction deformation toward the middle and upper parts of the slope. The critical volumetric water content during slope failure is approximately 53%. Granite residual soil is in a state of high volumetric water content under heavy rainfall conditions, and the shear strength decreases, resulting in a decrease in stability and finally failure occurrence. The new free face generated after failure constitutes an adverse condition for continued traction deformation and failure. As the soil permeability(cm/h) is less than the rainfall intensity(mm/h), and it is difficult for rainwater to continuously infiltrate in short-term rainfall, the influence depth of heavy rainfall is limited. The load of loose deposits at the slope foot also limits the development of deep deformation and failure. With the continuous effect of heavy rainfall, the surface runoff increases gradually, and the influence mode changes from instability failure caused by rainfall infiltration to erosion and scouring of surface runoff on slope surface. Transportation of loose materials by surface runoff is an important reason for prominent siltation in disaster-prone areas.
基金supported by the National Natural Science Foundation of China(Grant No.51275250)the Natural Science Foundation of Jiangsu Province(Grant No.BK2010457)the Agricultural Machinery Foundation of Jiangsu Province(Grant No.GXZ14003)
文摘A constitutive model on the evolution of debris flow with and without a barrier was established based on the theory of the Bingham model. A certain area of the Laoshan Mountain in Nanjing, Jiangsu Province, in China was chosen for experimental study, and the slope sliding and debris flow detection system was utilized. The change curve of the soil moisture content was attained, demonstrating that the moisture content of the shallow soil layer increases faster than that of the deep soil layer, and that the growth rate of the soil moisture content of the steep slope is large under the first weak rainfall, and that of the gentle slope is significantly affected by the second heavy rainfall. For the steep slope, slope sliding first occurs on the upper slope surface under heavy rainfall and further develops along the top platform and lower slope surface, while under weak rainfall the soil moisture content at the lower part of the slope first increases because of the high runoff velocity, meaning that failure occurring there is more serious. When a barrier was placed at a high position on a slope, debris flow was separated and distributed early and had less ability to carry solids, and the variation of the greatest depth of erosion pits on soil slopes was not significant.
基金Project(2006AA09Z235) supported by National High Technology Research and Development Program of ChinaProject(CX2009B003) supported by Hunan Provincial Innovation Foundation For Postgraduate,China
文摘The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment,which realizes the multi-motion modes of the autonomous underwater vehicle(AUV) such as vectored thruster and wheeled movement.In order to study the interactional principle between the hull and the wheel propellers while the AUV navigating in water,the computational fluid dynamics(CFD) method is used to simulate numerically the unsteady viscous flow around AUV with propellers by using the Reynolds-averaged Navier-Stokes(RANS) equations,shear-stress transport(SST) k-w model and pressure with splitting of operators(PISO) algorithm based on sliding mesh.The hydrodynamic parameters of AUV with propellers such as resistance,pressure and velocity are got,which reflect well the real ambient flow field of AUV with propellers.Then,the semi-implicit method for pressure-linked equations(SIMPLE) algorithm is used to compute the steady viscous flow field of AUV hull and propellers,respectively.The computational results agree well with the experimental data,which shows that the numerical method has good accuracy in the prediction of hydrodynamic performance.The interaction between AUV hull and wheel propellers is predicted qualitatively and quantitatively by comparing the hydrodynamic parameters such as resistance,pressure and velocity with those from integral computation and partial computation of the viscous flow around AUV with propellers,which provides an effective reference to the study on noise and vibration of AUV hull and propellers in real environment.It also provides technical support for the design of new AUVs.
