Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading stra...Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading strain rate was changed many times by a factor of up to 1 000 during otherwise monotonous loading at a constant axial strain rate. Test results show that the stress jump upon a stepwise change in the strain rate decays with an increase in the irreversible strain when monotonous loading continues at the changed strain rate and the amount of stress jump is essentially proportional to the instantaneous stress. Based on the amount of these stress jumps, a parameter fl called the rate-sensitivity coefficient is introduced to represent the quantity of the observed viscous properties of sand, which equals 0.021 3 and 0.024 2 respectively for Hostun and Toyoura sands. Further analyses on the results indicate that the effect of the presence of pore water is deemed to be negligible with sand and the fl value is rather independent of loading method, wet condition and confining pressure.展开更多
Attitude adjustment is a key link in the installation process of underwater facilities in deep water.To solve this problem,an omnidirectional spirit level for deep water was developed.The sealing principle of the spir...Attitude adjustment is a key link in the installation process of underwater facilities in deep water.To solve this problem,an omnidirectional spirit level for deep water was developed.The sealing principle of the spirit level and the principle of deep-water pressure resistance are analyzed,and the threaded connection strength is checked.The mechanical simulation verifies that the spirit level can withstand the pressure of 2000 m water depth,and the water pressure test is carried out for 30 min in a 20 MPa hyperbaric chamber.After the experiment is completed,the appearance of the spirit level is intact and there is no leakage.The experiment results show that the deep-water omnidirectional spirit level can be used in the deep sea within 2000 m.展开更多
基金Project(50679056) supported by the National Natural Science Foundation of ChinaProject(06-0378) supported by Program for NewCentury Excellent Talents in University+1 种基金Project(05SG25) supported by the "Dawn" Program of Shanghai Education Commission, ChinaProject(B308) supported by the Shanghai Leading Academic Discipline, China
文摘Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading strain rate was changed many times by a factor of up to 1 000 during otherwise monotonous loading at a constant axial strain rate. Test results show that the stress jump upon a stepwise change in the strain rate decays with an increase in the irreversible strain when monotonous loading continues at the changed strain rate and the amount of stress jump is essentially proportional to the instantaneous stress. Based on the amount of these stress jumps, a parameter fl called the rate-sensitivity coefficient is introduced to represent the quantity of the observed viscous properties of sand, which equals 0.021 3 and 0.024 2 respectively for Hostun and Toyoura sands. Further analyses on the results indicate that the effect of the presence of pore water is deemed to be negligible with sand and the fl value is rather independent of loading method, wet condition and confining pressure.
基金National key R&D Program of China(No.2017YFF0108104)Tianjin key R&D Program(No.20YFZCGX00550)。
文摘Attitude adjustment is a key link in the installation process of underwater facilities in deep water.To solve this problem,an omnidirectional spirit level for deep water was developed.The sealing principle of the spirit level and the principle of deep-water pressure resistance are analyzed,and the threaded connection strength is checked.The mechanical simulation verifies that the spirit level can withstand the pressure of 2000 m water depth,and the water pressure test is carried out for 30 min in a 20 MPa hyperbaric chamber.After the experiment is completed,the appearance of the spirit level is intact and there is no leakage.The experiment results show that the deep-water omnidirectional spirit level can be used in the deep sea within 2000 m.
