In order to control the lateral motion of a jet trencher which is important for stable trenching operation,the oscillation characteristics of the jet trencher are researched. The jet trencher is simplified into a sing...In order to control the lateral motion of a jet trencher which is important for stable trenching operation,the oscillation characteristics of the jet trencher are researched. The jet trencher is simplified into a single degree of freedom model with restoring and damping force. The nonlinear mathematical model of the trencher laterally oscillating in ocean currents is established,and its approximate analytical solution is obtained.Results show that the analytical solution has small differences with numerical solution based on the fourth-order Runge-Kutta method and can effectively describe the underwater oscillation. A double-loop PID controller is designed to control the lateral motion displacement of the trencher to return to the center of the pipeline route which is effective and robust for the propulsion system.展开更多
Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field.However,they are...Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field.However,they are not suit for soft seafloor with flow surface and high water content. Based on comprehensive analysis of seafloor soil shear deformation and track segment shear tests,a new empirical model of shear stressdisplacement relationship for saturated soft-plastic soil(SSP model) was proposed. To validate the SSP model and evaluate potential tractive force of self-propelled seafloor trencher,a test platform,where track segment shear test and drawbar pull test can be performed in seafloor soil substitute(bentonite water mixture),was built. Series of shear tests were carried out. Test results show that the SSP model can describe the mechanical behavior of track segment in seafloor soil substitute with good approximation. Through analyzing the main external forces,including environmental loads from seafloor soil and sea current applied to seafloor tracked trencher during the trenching process in a straight line,drawbar pull analysis model was deduced with the SSP model. A scale test model of seafloor tracked trencher was built,and the verification tests for drawbar pull analysis model were designed and carried out. Results of verification tests indicate that the drawbar pull analysis model was feasible and effective. The drawbar pull tests also indicated that the SSP model is valid from another side.展开更多
A computer program was developed in C++language to predict the effect of soil bulk density on draft force on bottoms,share thickness,stresses distribution and maximum deflection on standards,bending stresses distribut...A computer program was developed in C++language to predict the effect of soil bulk density on draft force on bottoms,share thickness,stresses distribution and maximum deflection on standards,bending stresses distribution on side plates,diameter of shear pins,and tensile stress on hitch bar.It was found that,as soil bulk density increased,stresses distribution and maximum deflection on standards,bending stresses distribution on side plates,diameter of shear pins,and tensile stress on hitch bar increased.The diameter of shear pin should be larger to meet wide range of soil density.展开更多
为了保证海底管道与缆线的安全和稳定,人们采用了许多措施。其中,最为经济有效的方法是利用开沟机等相关设备将管道或缆线埋入海底。本文研究水下开沟,设计了一款具有轻型结构、可自主推进的水下射流开沟机,并对加工完成后的样机模型开...为了保证海底管道与缆线的安全和稳定,人们采用了许多措施。其中,最为经济有效的方法是利用开沟机等相关设备将管道或缆线埋入海底。本文研究水下开沟,设计了一款具有轻型结构、可自主推进的水下射流开沟机,并对加工完成后的样机模型开展了水下开沟的试验。验证了所设计的开沟机在淹没状态下不仅可以完成自主推进工作,还能在管道流量达到50 m 3/h时破坏抗剪强度为8 kPa的沙土,最大沟深可达0.41 m,为后续的模型优化以及管线埋设提供理论与依据。展开更多
基金Sponsored by the High Technology Ship Research and Program of Ministry of Industry and Information Technology of the People's Republic of China(Grant No.539[2012])the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120073120014)
文摘In order to control the lateral motion of a jet trencher which is important for stable trenching operation,the oscillation characteristics of the jet trencher are researched. The jet trencher is simplified into a single degree of freedom model with restoring and damping force. The nonlinear mathematical model of the trencher laterally oscillating in ocean currents is established,and its approximate analytical solution is obtained.Results show that the analytical solution has small differences with numerical solution based on the fourth-order Runge-Kutta method and can effectively describe the underwater oscillation. A double-loop PID controller is designed to control the lateral motion displacement of the trencher to return to the center of the pipeline route which is effective and robust for the propulsion system.
文摘Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field.However,they are not suit for soft seafloor with flow surface and high water content. Based on comprehensive analysis of seafloor soil shear deformation and track segment shear tests,a new empirical model of shear stressdisplacement relationship for saturated soft-plastic soil(SSP model) was proposed. To validate the SSP model and evaluate potential tractive force of self-propelled seafloor trencher,a test platform,where track segment shear test and drawbar pull test can be performed in seafloor soil substitute(bentonite water mixture),was built. Series of shear tests were carried out. Test results show that the SSP model can describe the mechanical behavior of track segment in seafloor soil substitute with good approximation. Through analyzing the main external forces,including environmental loads from seafloor soil and sea current applied to seafloor tracked trencher during the trenching process in a straight line,drawbar pull analysis model was deduced with the SSP model. A scale test model of seafloor tracked trencher was built,and the verification tests for drawbar pull analysis model were designed and carried out. Results of verification tests indicate that the drawbar pull analysis model was feasible and effective. The drawbar pull tests also indicated that the SSP model is valid from another side.
文摘A computer program was developed in C++language to predict the effect of soil bulk density on draft force on bottoms,share thickness,stresses distribution and maximum deflection on standards,bending stresses distribution on side plates,diameter of shear pins,and tensile stress on hitch bar.It was found that,as soil bulk density increased,stresses distribution and maximum deflection on standards,bending stresses distribution on side plates,diameter of shear pins,and tensile stress on hitch bar increased.The diameter of shear pin should be larger to meet wide range of soil density.
文摘为了保证海底管道与缆线的安全和稳定,人们采用了许多措施。其中,最为经济有效的方法是利用开沟机等相关设备将管道或缆线埋入海底。本文研究水下开沟,设计了一款具有轻型结构、可自主推进的水下射流开沟机,并对加工完成后的样机模型开展了水下开沟的试验。验证了所设计的开沟机在淹没状态下不仅可以完成自主推进工作,还能在管道流量达到50 m 3/h时破坏抗剪强度为8 kPa的沙土,最大沟深可达0.41 m,为后续的模型优化以及管线埋设提供理论与依据。
