Soil behavior can reflect the characteristics of principal stress rotation under dynamic wave and traffic loads. Unequal amplitudes of tensile and compressive stresses applied to soils have complex effects on foundati...Soil behavior can reflect the characteristics of principal stress rotation under dynamic wave and traffic loads. Unequal amplitudes of tensile and compressive stresses applied to soils have complex effects on foundation soils in comparison with the pure principal stress rotation path. A series of undrained cyclic hollow torsional shear tests were performed on typical remolded soft clay from the Hexi area of Nanjing, China. The main control parameters were the tensile and compressive stress amplitude ratio(α) and the cyclic dynamic stress ratio(η). It was found that the critical η tended to remain constant at 0.13, when the value of the compressive stress amplitude was higher than the tensile stress amplitude. However, the influence of the tensile stress was limited by the dynamic stress level when α= 1.For obvious structural change in the soil, the corresponding numbers of cyclic vibration cycles were found to be independent of α at low stress levels and were only related to η. Finally, a new method for evaluating the failure of remolded soft clay was presented. It considers the influence of the tensile and compressive stresses which caused by complex stress paths of the principal stress rotation. This criterion can distinguish stable, critical, and destructive states based on the pore-water-pressure-strain coupling curve while also providing a range of failure strain and vibration cycles. These results provide the theoretical support for systematic studies of principal stress rotation using constitutive models.展开更多
The computation of the all-pairs shortest paths is an important graph algorithmic problem.When the graph changes,such as edge deletions/insertions,recalculating the shortest distance of a graph from scratch is costly....The computation of the all-pairs shortest paths is an important graph algorithmic problem.When the graph changes,such as edge deletions/insertions,recalculating the shortest distance of a graph from scratch is costly.In this paper,we investigate how to quickly maintain the shortest distance of the dynamic graph in the distributed memory system.For a distributed system with p processors,the state-of-art algorithm to recompute the shortest distance of a graph with n vertices from scratch requires O(n^(2)/√p)bandwidth cost and O(√plog^(2)p)latency cost.For the insertion of k edges,we give an incremental algorithm with a bandwidth cost of O(nk√p+k^(2))and a latency cost of O(logp).For typical scenarios where k=O(n/√p),the bandwidth and latency costs are reduced by a factor of O(√p)and O(√plogp),respectively.For the deletion of k edges,we give a decremental algorithm with a bandwidth cost of O(nk/√p+k^(2)+n^(2)/log^(3)p+|S|^(2)logp)and a latency cost of O(log^(3)p),where S is the separator size of a constructed graph and is related to the alteration degree of the shortest path of the dynamic graph.When k=O(n/√p)and S=O(n/√p),the bandwidth and latency costs are reduced by a factor of O(√p∕log^(3)p)and O(√p∕logp),respectively.展开更多
基金financial support of the National Natural Science Foundation of China(51420105013 and 51479060)Fundamental Research Funds for the Central Universities(2015B17114)Science and Technology Project of Shandong Housing and Urban-Rural Development(2014QG009)
文摘Soil behavior can reflect the characteristics of principal stress rotation under dynamic wave and traffic loads. Unequal amplitudes of tensile and compressive stresses applied to soils have complex effects on foundation soils in comparison with the pure principal stress rotation path. A series of undrained cyclic hollow torsional shear tests were performed on typical remolded soft clay from the Hexi area of Nanjing, China. The main control parameters were the tensile and compressive stress amplitude ratio(α) and the cyclic dynamic stress ratio(η). It was found that the critical η tended to remain constant at 0.13, when the value of the compressive stress amplitude was higher than the tensile stress amplitude. However, the influence of the tensile stress was limited by the dynamic stress level when α= 1.For obvious structural change in the soil, the corresponding numbers of cyclic vibration cycles were found to be independent of α at low stress levels and were only related to η. Finally, a new method for evaluating the failure of remolded soft clay was presented. It considers the influence of the tensile and compressive stresses which caused by complex stress paths of the principal stress rotation. This criterion can distinguish stable, critical, and destructive states based on the pore-water-pressure-strain coupling curve while also providing a range of failure strain and vibration cycles. These results provide the theoretical support for systematic studies of principal stress rotation using constitutive models.
基金supported in part by National Natural Science Foundation of China under Grants 61972447 and 61832006.
文摘The computation of the all-pairs shortest paths is an important graph algorithmic problem.When the graph changes,such as edge deletions/insertions,recalculating the shortest distance of a graph from scratch is costly.In this paper,we investigate how to quickly maintain the shortest distance of the dynamic graph in the distributed memory system.For a distributed system with p processors,the state-of-art algorithm to recompute the shortest distance of a graph with n vertices from scratch requires O(n^(2)/√p)bandwidth cost and O(√plog^(2)p)latency cost.For the insertion of k edges,we give an incremental algorithm with a bandwidth cost of O(nk√p+k^(2))and a latency cost of O(logp).For typical scenarios where k=O(n/√p),the bandwidth and latency costs are reduced by a factor of O(√p)and O(√plogp),respectively.For the deletion of k edges,we give a decremental algorithm with a bandwidth cost of O(nk/√p+k^(2)+n^(2)/log^(3)p+|S|^(2)logp)and a latency cost of O(log^(3)p),where S is the separator size of a constructed graph and is related to the alteration degree of the shortest path of the dynamic graph.When k=O(n/√p)and S=O(n/√p),the bandwidth and latency costs are reduced by a factor of O(√p∕log^(3)p)and O(√p∕logp),respectively.
