To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory ...To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, howeve~ further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.展开更多
Root pullout property of plants was of key importance to the soil reinforcement and the improvement of slope stability. To investigate the influence of soil moisture on root pullout resistance and failure modes in soi...Root pullout property of plants was of key importance to the soil reinforcement and the improvement of slope stability. To investigate the influence of soil moisture on root pullout resistance and failure modes in soil reinforcement process, we conducted pullout tests on alfalfa(Medicago sativa L.) roots at five levels(40, 30, 20, 10 and 6 kPa) of soil matric suction, corresponding to respectively 7.84%, 9.66%, 13.02%, 19.35% and 27.06% gravimetric soil moisture contents. Results showed that the maximal root pullout force of M. sativa decreased in a power function with increasing soil moisture content from 7.84% to 27.06%. Root slippage rate increased and breakage rate decreased with increasing soil moisture content. At 9.66% soil moisture content, root slippage rate and breakage rate was 56.41% and 43.58%, respectively. The threshold value of soil moisture content was about 9.00% for alfalfa roots in the loess soil. The maximal pullout force of M. sativa increased with root diameter in a power function. The threshold value of root diameter was 1.15 mm, because root slipping force was greater than root breaking force when diameter >1.15 mm, while diameter ≤1.15 mm, root slipping force tended to be less than root breaking force. No significant difference in pullout forces was observed between slipping roots and breaking roots when they had similar diameters. More easily obtained root tensile force(strength) is suggested to be used in root reinforcement models under the condition that the effect of root diameter is excluded as the pullout force of breaking roots measured in pullout tests is similar to the root tensile force obtained by tensile tests.展开更多
基金Project(2009B13014) supported by the Fundamental Research Funds for the Central Universities of ChinaProject(IRT1125) supported by the Program for Changjiang Scholars and Innovative Research Team in University,China
文摘To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, howeve~ further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.
基金funded by the National Natural Science Foundation of China (31600582)the Natural Science Foundation of Shanxi Province of China (201701D221224)+2 种基金the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province of China (2017)the Scientific and Technological Innovation Programs of Higher Education Institutions of Shanxi Province, China (2019L0175)the National Key Research and Development Program of China (2018YFC0407803)。
文摘Root pullout property of plants was of key importance to the soil reinforcement and the improvement of slope stability. To investigate the influence of soil moisture on root pullout resistance and failure modes in soil reinforcement process, we conducted pullout tests on alfalfa(Medicago sativa L.) roots at five levels(40, 30, 20, 10 and 6 kPa) of soil matric suction, corresponding to respectively 7.84%, 9.66%, 13.02%, 19.35% and 27.06% gravimetric soil moisture contents. Results showed that the maximal root pullout force of M. sativa decreased in a power function with increasing soil moisture content from 7.84% to 27.06%. Root slippage rate increased and breakage rate decreased with increasing soil moisture content. At 9.66% soil moisture content, root slippage rate and breakage rate was 56.41% and 43.58%, respectively. The threshold value of soil moisture content was about 9.00% for alfalfa roots in the loess soil. The maximal pullout force of M. sativa increased with root diameter in a power function. The threshold value of root diameter was 1.15 mm, because root slipping force was greater than root breaking force when diameter >1.15 mm, while diameter ≤1.15 mm, root slipping force tended to be less than root breaking force. No significant difference in pullout forces was observed between slipping roots and breaking roots when they had similar diameters. More easily obtained root tensile force(strength) is suggested to be used in root reinforcement models under the condition that the effect of root diameter is excluded as the pullout force of breaking roots measured in pullout tests is similar to the root tensile force obtained by tensile tests.
