A scheme is developed for analysing the interaction between afoundation and a nonlin- ear rock and soil medium, in which thefoundation is considered as a linear elastic body and a typicalboundary integral equation met...A scheme is developed for analysing the interaction between afoundation and a nonlin- ear rock and soil medium, in which thefoundation is considered as a linear elastic body and a typicalboundary integral equation method (BIEM) is employed. On the basis oftaking the nonlinear proper- ties of the medium into account, aperturbation BIEM is developed. The fundamental equations for thenonlinear coupling analysis are formulated, and typical problems aresolved and discussed by the pre- sent method.展开更多
The engineering and geological characteristics of a steep slope consisting of coal gangue, rock and soil medium in Huating coal mine have been comprehensively investigated. Owing to humid weather, heavy rainfall, vege...The engineering and geological characteristics of a steep slope consisting of coal gangue, rock and soil medium in Huating coal mine have been comprehensively investigated. Owing to humid weather, heavy rainfall, vegetation and porous characteristics of the soil and rock mass, the steep slope will be destabilized and induce mud-rock flow or derive hazard easily. Firstly, based on the classical slope reinforcement theory, some regularity between the shear and displacement in the destabilized zone of the slope with or without root strength contribution is presented. Then, based on the experimental and statistical analysis of root strength, hydrological characteristics and stability status, etc., some possible biotechnical techniques for reinforcement of the steep slope have been suggested. These methods are important for quantitative analysis of destabilization of the slope and design of the biotechnical reinforcement.展开更多
Electromagnetic scattering from a rough surface of layered medium is investigated, and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough s...Electromagnetic scattering from a rough surface of layered medium is investigated, and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough surface with exponential correlation function is presented for describing a rough soil surface of layered medium, the formula of its scattering coefficient is derived by considering the spectrum of the rough surface with exponential correlation function; the curves of the bistatic scattering coefficient of HH polarization with variation of the scattering angle are obtained by numerical calculation. The influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the roughness surface parameters and the frequency of the incident wave on the blstatic scattering coefficient is discussed. Numerical results show that the influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the rms and the correlation length of the rough surface, and the frequency of the incident wave on the bistatic scattering coefficient is very complex.展开更多
【目的】针对松散介质下钻进机器人研究匮乏、土壤-螺旋钻进机制分析不足的问题,设计一款新型螺旋钻进机器人,满足高效钻进与灵活避障的实际需求。【方法】首先,通过土壤-螺旋相互作用分析,建立运动学与动力学模型,揭示单螺旋钻进偏转...【目的】针对松散介质下钻进机器人研究匮乏、土壤-螺旋钻进机制分析不足的问题,设计一款新型螺旋钻进机器人,满足高效钻进与灵活避障的实际需求。【方法】首先,通过土壤-螺旋相互作用分析,建立运动学与动力学模型,揭示单螺旋钻进偏转的核心机制;其次,设计左旋-右旋-左旋组合推进机构以抵消偏转影响,搭配3R1T混联机构实现空间三维转向;再次,利用Matlab软件分析混联机构工作空间,验证转向灵活性;最后,建立离散元与多体动力学(Discrete Element and Multibody Dynamics, DEM-MBD)耦合仿真模型,全面验证机构性能。【结果】仿真结果表明,多螺旋组合使单螺旋偏转误差控制在3%以内,混联机构具备3R1T自由度与充足工作空间;机器人9 s内轴向钻进150 mm,竖直方向位移可控在35 mm内,可有效解决单螺旋偏转问题,实现松散介质下高效钻进与灵活转向。研究可为同类机器人设计提供参考。展开更多
Existing strength criteria are mostly formulated to describe the mechanical properties of reconstituted soils. However, the engineering characteristics of structured soils are different from those of reconstituted soi...Existing strength criteria are mostly formulated to describe the mechanical properties of reconstituted soils. However, the engineering characteristics of structured soils are different from those of reconstituted soils in many aspects, especially in their strength properties, Thus, the influence of soil structure （bonding and fabric） on the mechanical properties of structured soils cannot be correctly described, By analyzing the breakage mechanism of natural soils, the structured soils can be conceptualized as binary medium materials consisting of bonded blocks and weakened bands. On this basis, a new strength criterion is pro- posed for structured soils, The expressions of the strength criterion on both meridian and deviator planes are given to describe the strength properties of structured soils on these planes. The proposed strength criterion is compared with available test data under conventional and true triaxial stress conditions in the literature. It is observed that the proposed strength criterion agrees well with the test data.展开更多
This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot＇s poroelastic theory and the constitutive relations of the transversely isotropic medium, th...This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot＇s poroelastic theory and the constitutive relations of the transversely isotropic medium, the dynamic governing equations of the outer and inner transversely isotropic saturated soil layers are derived. The Laplace transform is used to solve the governing equations of the outer and inner soil layers. The dynamic torsional response of the pipe pile in the frequency domain is derived utilizing 1D elastic theory and the continuous conditions at the interfaces between the pipe pile and the soils. The time domain solution is obtained by Fourier inverse transform. A parametric study is conducted to demonstrate the influence of the anisotropies of the outer and inner soil on the torsional dynamic response of the pipe pile.展开更多
Mud inrush in mountain tunnel is an independent geological hazard type different from water inrush,landslide and debris flow.The intrinsic factor of mud inrush is the instability failure of disaster medium.Its essence...Mud inrush in mountain tunnel is an independent geological hazard type different from water inrush,landslide and debris flow.The intrinsic factor of mud inrush is the instability failure of disaster medium.Its essence is that when the cohesion decreases gradually with the increase of void ratio to the point where the movement of soil particles cannot be restricted,soil particles and groundwater form slurry and gush out.Thus,accurate calculation of cohesion with variable void ratios is crucial for analyzing the reliability of disaster medium.In this study,the disaster medium was regarded as graded soil and a structural model was established wherein soil particles were simplified as cubes and the inter-particle pores were represented by the clearance between cubes.On the basis of the structure model of disaster medium,a function between the soil particle distance and void ratio was derived.Cohesion is equivalent to the resultant force between soil particles per unit area;thus,a cohesion function was derived in which the void ratio is the main variable.This function considers the influence of gradation characteristics on cohesion variation and is generally applicable to various types of disaster medium.A series of direct shear tests were carried out to determine the cohesion variation for different types of disaster medium with variable void ratios.By comparing the variation of cohesion obtained through direct shear tests with those deduced by the proposed cohesion function,we verified the validity and general applicability of the cohesion function.It is of great significance because the cohesion function can accurately predict the variation of cohesion by using the void ratio,and effectively evaluate the possibility of mud inrush according to the initial mechanical properties of disaster medium.展开更多
Based on elasticity and the theory of saturated porous media, and regarding the pile and the soil as a single phase elastic and a saturated viscoelastic media, respectively, the dynamical behavior of vertical vibratio...Based on elasticity and the theory of saturated porous media, and regarding the pile and the soil as a single phase elastic and a saturated viscoelastic media, respectively, the dynamical behavior of vertical vibration of an end-bearing pile in a saturated viscoelastic soil layer is investigated in the frequency domain using the Helmholtz decomposition and variable separation method. The axisymmetrical analytical solutions for vertical vibrations of the pile in a saturated viscoelastic soil layer are obtained, and the analytical expression of the dynamical complex stiffness of the pile top is presented. Responses of dynamic stiffness factor and equivalent damping of pile top with respect to the frequency are shown in figures using a numerical method. Effects of the saturated soil parameters, modulus ratio of the pile to soil, slenderness ratio of pile and pile＇s Poisson ratio, etc. on the stiffness factor and damping are examined. It is shown that, due to the effect of the transversal deformation of the pile and the radial force of the saturated viscoelastic soil acting on the pile, the dynamic stiffness factor and the damping derived from the axisymmetrical solution are greatly different from those derived from the classical Euler-Bernoulli rod model, especially at some specific excitation frequencies. Therefore, there are limitations on applicability of the Euler-Bernoulli rod model in analyzing verticai vibration of the pile. More accurate analysis should be based on a three-dimensional model.展开更多
The aim of the study was to determine the effect of soil fertilizers, used on the background of NPK fertilization on the productivity of Lolium perenne and Lolium multiflorum in different time of harvest. In 2012-2013...The aim of the study was to determine the effect of soil fertilizers, used on the background of NPK fertilization on the productivity of Lolium perenne and Lolium multiflorum in different time of harvest. In 2012-2013 the following species and varieties of forage grasses： Lolium perenne and Lolium multiflorum were cultivated. It was the fallowing experimental subjects： K-control （without fertilization and fertilizer）, NPK （N-150 kg hal as a 34% ammonium nitrate, P-80 kg P2O5 ha-1, K-120 kg K20 ha-1）, UG-UGmax bio-preparation, EU-Eco bio-preparation （fertilizer）, HA-Humus Active as bio-preparation.展开更多
Based on elasto-plasticity and damage mechanics, a double-medium constitutive model of geological material under uniaxial tension and compression was presented, on the assumption that rock and soil materials are the p...Based on elasto-plasticity and damage mechanics, a double-medium constitutive model of geological material under uniaxial tension and compression was presented, on the assumption that rock and soil materials are the pore-fracture double-medium, and porous medium has no damage occurring, while fracture medium has damage occurring with load. To the implicit equation of the model, iterative method was adopted to obtain the complete stress-strain curve of the material. The result shows that many different distributions （uniform distribution, concentrated distribution and random distribution） of fractures in rock and soil material are the essential reasons of the daedal constitutive relations. By the reason that the double-medium constitutive model separates the material to be porous medium part, which is the main body of elasticity, and fracture medium part, which is the main body of damage, it is of important practical values and theoretical meanings to the study on failure of rock and soil or materials containing damage.展开更多
文摘A scheme is developed for analysing the interaction between afoundation and a nonlin- ear rock and soil medium, in which thefoundation is considered as a linear elastic body and a typicalboundary integral equation method (BIEM) is employed. On the basis oftaking the nonlinear proper- ties of the medium into account, aperturbation BIEM is developed. The fundamental equations for thenonlinear coupling analysis are formulated, and typical problems aresolved and discussed by the pre- sent method.
基金This work was financially supported by the National Natural Science Foundation of China (No. 10402033) and the Key Lab. Foun-dation of the Ministry of Education of China (No.04JS19).
文摘The engineering and geological characteristics of a steep slope consisting of coal gangue, rock and soil medium in Huating coal mine have been comprehensively investigated. Owing to humid weather, heavy rainfall, vegetation and porous characteristics of the soil and rock mass, the steep slope will be destabilized and induce mud-rock flow or derive hazard easily. Firstly, based on the classical slope reinforcement theory, some regularity between the shear and displacement in the destabilized zone of the slope with or without root strength contribution is presented. Then, based on the experimental and statistical analysis of root strength, hydrological characteristics and stability status, etc., some possible biotechnical techniques for reinforcement of the steep slope have been suggested. These methods are important for quantitative analysis of destabilization of the slope and design of the biotechnical reinforcement.
基金supported by the National Natural Science Foundation of China (Grant No 60571058)the Specialized Research Fund for the Doctoral Program of Higher Education Institutions of China (Grant No 20070701010)
文摘Electromagnetic scattering from a rough surface of layered medium is investigated, and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough surface with exponential correlation function is presented for describing a rough soil surface of layered medium, the formula of its scattering coefficient is derived by considering the spectrum of the rough surface with exponential correlation function; the curves of the bistatic scattering coefficient of HH polarization with variation of the scattering angle are obtained by numerical calculation. The influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the roughness surface parameters and the frequency of the incident wave on the blstatic scattering coefficient is discussed. Numerical results show that the influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the rms and the correlation length of the rough surface, and the frequency of the incident wave on the bistatic scattering coefficient is very complex.
文摘【目的】针对松散介质下钻进机器人研究匮乏、土壤-螺旋钻进机制分析不足的问题,设计一款新型螺旋钻进机器人,满足高效钻进与灵活避障的实际需求。【方法】首先,通过土壤-螺旋相互作用分析,建立运动学与动力学模型,揭示单螺旋钻进偏转的核心机制;其次,设计左旋-右旋-左旋组合推进机构以抵消偏转影响,搭配3R1T混联机构实现空间三维转向;再次,利用Matlab软件分析混联机构工作空间,验证转向灵活性;最后,建立离散元与多体动力学(Discrete Element and Multibody Dynamics, DEM-MBD)耦合仿真模型,全面验证机构性能。【结果】仿真结果表明,多螺旋组合使单螺旋偏转误差控制在3%以内,混联机构具备3R1T自由度与充足工作空间;机器人9 s内轴向钻进150 mm,竖直方向位移可控在35 mm内,可有效解决单螺旋偏转问题,实现松散介质下高效钻进与灵活转向。研究可为同类机器人设计提供参考。
文摘Existing strength criteria are mostly formulated to describe the mechanical properties of reconstituted soils. However, the engineering characteristics of structured soils are different from those of reconstituted soils in many aspects, especially in their strength properties, Thus, the influence of soil structure （bonding and fabric） on the mechanical properties of structured soils cannot be correctly described, By analyzing the breakage mechanism of natural soils, the structured soils can be conceptualized as binary medium materials consisting of bonded blocks and weakened bands. On this basis, a new strength criterion is pro- posed for structured soils, The expressions of the strength criterion on both meridian and deviator planes are given to describe the strength properties of structured soils on these planes. The proposed strength criterion is compared with available test data under conventional and true triaxial stress conditions in the literature. It is observed that the proposed strength criterion agrees well with the test data.
基金The 111 Project under Grant No.B13024the National Natural Science Foundation of China under Grant Nos.U1134207 and 51378177the Program for New Century Excellent Talents in University under Grant No.NCET-12-0843
文摘This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot＇s poroelastic theory and the constitutive relations of the transversely isotropic medium, the dynamic governing equations of the outer and inner transversely isotropic saturated soil layers are derived. The Laplace transform is used to solve the governing equations of the outer and inner soil layers. The dynamic torsional response of the pipe pile in the frequency domain is derived utilizing 1D elastic theory and the continuous conditions at the interfaces between the pipe pile and the soils. The time domain solution is obtained by Fourier inverse transform. A parametric study is conducted to demonstrate the influence of the anisotropies of the outer and inner soil on the torsional dynamic response of the pipe pile.
基金funded by the National Natural Science Foundation of China(Grant No.U1706223)the Natural Science Foundation of Shandong Province(Grant No.ZR2017MEE070)
文摘Mud inrush in mountain tunnel is an independent geological hazard type different from water inrush,landslide and debris flow.The intrinsic factor of mud inrush is the instability failure of disaster medium.Its essence is that when the cohesion decreases gradually with the increase of void ratio to the point where the movement of soil particles cannot be restricted,soil particles and groundwater form slurry and gush out.Thus,accurate calculation of cohesion with variable void ratios is crucial for analyzing the reliability of disaster medium.In this study,the disaster medium was regarded as graded soil and a structural model was established wherein soil particles were simplified as cubes and the inter-particle pores were represented by the clearance between cubes.On the basis of the structure model of disaster medium,a function between the soil particle distance and void ratio was derived.Cohesion is equivalent to the resultant force between soil particles per unit area;thus,a cohesion function was derived in which the void ratio is the main variable.This function considers the influence of gradation characteristics on cohesion variation and is generally applicable to various types of disaster medium.A series of direct shear tests were carried out to determine the cohesion variation for different types of disaster medium with variable void ratios.By comparing the variation of cohesion obtained through direct shear tests with those deduced by the proposed cohesion function,we verified the validity and general applicability of the cohesion function.It is of great significance because the cohesion function can accurately predict the variation of cohesion by using the void ratio,and effectively evaluate the possibility of mud inrush according to the initial mechanical properties of disaster medium.
基金Project supported by the National Natural Science Foundation of China (No. 10872124)
文摘Based on elasticity and the theory of saturated porous media, and regarding the pile and the soil as a single phase elastic and a saturated viscoelastic media, respectively, the dynamical behavior of vertical vibration of an end-bearing pile in a saturated viscoelastic soil layer is investigated in the frequency domain using the Helmholtz decomposition and variable separation method. The axisymmetrical analytical solutions for vertical vibrations of the pile in a saturated viscoelastic soil layer are obtained, and the analytical expression of the dynamical complex stiffness of the pile top is presented. Responses of dynamic stiffness factor and equivalent damping of pile top with respect to the frequency are shown in figures using a numerical method. Effects of the saturated soil parameters, modulus ratio of the pile to soil, slenderness ratio of pile and pile＇s Poisson ratio, etc. on the stiffness factor and damping are examined. It is shown that, due to the effect of the transversal deformation of the pile and the radial force of the saturated viscoelastic soil acting on the pile, the dynamic stiffness factor and the damping derived from the axisymmetrical solution are greatly different from those derived from the classical Euler-Bernoulli rod model, especially at some specific excitation frequencies. Therefore, there are limitations on applicability of the Euler-Bernoulli rod model in analyzing verticai vibration of the pile. More accurate analysis should be based on a three-dimensional model.
文摘The aim of the study was to determine the effect of soil fertilizers, used on the background of NPK fertilization on the productivity of Lolium perenne and Lolium multiflorum in different time of harvest. In 2012-2013 the following species and varieties of forage grasses： Lolium perenne and Lolium multiflorum were cultivated. It was the fallowing experimental subjects： K-control （without fertilization and fertilizer）, NPK （N-150 kg hal as a 34% ammonium nitrate, P-80 kg P2O5 ha-1, K-120 kg K20 ha-1）, UG-UGmax bio-preparation, EU-Eco bio-preparation （fertilizer）, HA-Humus Active as bio-preparation.
基金Project supported by the National Natural Science Foundation of China (No.50374041)the National Key Project of the Tenth Five-Year Plan of China (No.2001BA803B0404)
文摘Based on elasto-plasticity and damage mechanics, a double-medium constitutive model of geological material under uniaxial tension and compression was presented, on the assumption that rock and soil materials are the pore-fracture double-medium, and porous medium has no damage occurring, while fracture medium has damage occurring with load. To the implicit equation of the model, iterative method was adopted to obtain the complete stress-strain curve of the material. The result shows that many different distributions （uniform distribution, concentrated distribution and random distribution） of fractures in rock and soil material are the essential reasons of the daedal constitutive relations. By the reason that the double-medium constitutive model separates the material to be porous medium part, which is the main body of elasticity, and fracture medium part, which is the main body of damage, it is of important practical values and theoretical meanings to the study on failure of rock and soil or materials containing damage.
