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
Large-scale urban events like the Olympic Games,the World Expo,etc.,have brought about an "approach" leading to renewed conservation measures for old city areas.While they make many heritages receive better ...Large-scale urban events like the Olympic Games,the World Expo,etc.,have brought about an "approach" leading to renewed conservation measures for old city areas.While they make many heritages receive better protection,they also create new problem of "threshold" to heritage conservation;thus,ideas about the effects of large-scale urban events on cultural heritage preservation are polarized into two opposite directions.Using cultural anthropology as the basis of analysis,this article interprets how these conflicting concepts came to be.As large-scale urban events accelerate and strengthen urban development,they also often cause the abandonment of specific cultural elements during the process of heritage conservation for the oldest city areas.This leads to a general loss of direction in cultural protection efforts.A potential solution is to unearth the cultural spirit of the old cities and preserve it through practical technologies,in considering the specific function of large-scale urban events.In so doing,it is possible to explore new directions and approaches to conserve the heritages of the old city under the guide of urban cultural development strategies.展开更多
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.
文摘Large-scale urban events like the Olympic Games,the World Expo,etc.,have brought about an "approach" leading to renewed conservation measures for old city areas.While they make many heritages receive better protection,they also create new problem of "threshold" to heritage conservation;thus,ideas about the effects of large-scale urban events on cultural heritage preservation are polarized into two opposite directions.Using cultural anthropology as the basis of analysis,this article interprets how these conflicting concepts came to be.As large-scale urban events accelerate and strengthen urban development,they also often cause the abandonment of specific cultural elements during the process of heritage conservation for the oldest city areas.This leads to a general loss of direction in cultural protection efforts.A potential solution is to unearth the cultural spirit of the old cities and preserve it through practical technologies,in considering the specific function of large-scale urban events.In so doing,it is possible to explore new directions and approaches to conserve the heritages of the old city under the guide of urban cultural development strategies.
