Bed protection in apron downstream was installed to use riprap or gabion mattress. In the case of bed protection using riprap, the decision on the riprap diameter is very important because riprap diameter means the ca...Bed protection in apron downstream was installed to use riprap or gabion mattress. In the case of bed protection using riprap, the decision on the riprap diameter is very important because riprap diameter means the capacity to withstand the flow. Initial formulas for the decision on the riprap diameter applied velocity and weight as main factors. Since the main factors gradually expanded to depth, bed slope, and turbulence intensity, decision formulas for the riprap diameter were detailed. Because turbulence intensity was considered to be a main factor of the formula, the decision formulas for the riprap diameter could be expanded to apply to bed protection around hydraulic structures. Escarameia and May conducted a study on the riprap diameter of a strong turbulence area around the downstream of hydraulic structures. For the formula of Escarameia and May, the basis of the formula was the Izbash type, and the main factor was turbulence intensity. This study was an experimental study for deciding the riprap diameter installed around apron downstream and was based on the study results of Escarameia and May. The experiment measured the velocity upon change of discharge and riprap diameter to the installed weir model and analyzed the correlation of threshold velocity by diameter. The experimental formula in this study expanded the turbulence intensity limits of the Escarameia and May formula and increased application to turbulence intensity in weir downstream.展开更多
The riprap air-cooled roadbed and common roadbed experimental project were designed and carried on in Qingshuihe test filed, an area of warm permafrost category with the fine frozen soil along Qinghai-Tibet Railway, t...The riprap air-cooled roadbed and common roadbed experimental project were designed and carried on in Qingshuihe test filed, an area of warm permafrost category with the fine frozen soil along Qinghai-Tibet Railway, to decide the temperature field of the roadbed after railway construction. Based on ground temperature variation of natural hole, left and right shoulder’s hole, the maximum thawing depth, and the deformation in these two kinds of roadbed were analysed comparatively. It showed that the riprap air-cooled roadbed had better effect of lowering ground temperature, lifting the maximum frozen-thawing depth obviously and decreasing deformation than that of the common roadbed. Therefore, the riprap air-cooled roadbed was a positive frozen soil protection measure for it effectively decreased ground temperature and protected permafrost.展开更多
Rubble mound breakwaters, a prevalent type of sloping breakwater structure, are extensively employed in port and coastal infrastructure projects. Under soft soil foundation conditions, the process of squeezing silt by...Rubble mound breakwaters, a prevalent type of sloping breakwater structure, are extensively employed in port and coastal infrastructure projects. Under soft soil foundation conditions, the process of squeezing silt by riprap is implemented to enhance bearing capacity through soft soil replacement and compaction. However, predicting the depth law of squeezing silt by riprap and understanding its mechanism remain significant engineering design challenges.This study employs particle flow code(PFC) based on the discrete element method to simulate the squeezing silt process by riprap, examining variations in depth law under different geological conditions and its mechanical characteristics.Through calibration of the PFC model's meso-parameters via macro-experiments, the study analyzes the effects of riprap size, drop height, and soft soil properties on the depth law of squeezing silt. Findings demonstrate that riprap drop height and soft soil thickness substantially influence the depth, while appropriate calibration of meso-parameters enhances simulation accuracy. This research contributes theoretical and practical guidance for optimizing rubble mound breakwater design, understanding squeezing silt mechanisms, construction practices, and riprap quantity estimation.展开更多
文摘Bed protection in apron downstream was installed to use riprap or gabion mattress. In the case of bed protection using riprap, the decision on the riprap diameter is very important because riprap diameter means the capacity to withstand the flow. Initial formulas for the decision on the riprap diameter applied velocity and weight as main factors. Since the main factors gradually expanded to depth, bed slope, and turbulence intensity, decision formulas for the riprap diameter were detailed. Because turbulence intensity was considered to be a main factor of the formula, the decision formulas for the riprap diameter could be expanded to apply to bed protection around hydraulic structures. Escarameia and May conducted a study on the riprap diameter of a strong turbulence area around the downstream of hydraulic structures. For the formula of Escarameia and May, the basis of the formula was the Izbash type, and the main factor was turbulence intensity. This study was an experimental study for deciding the riprap diameter installed around apron downstream and was based on the study results of Escarameia and May. The experiment measured the velocity upon change of discharge and riprap diameter to the installed weir model and analyzed the correlation of threshold velocity by diameter. The experimental formula in this study expanded the turbulence intensity limits of the Escarameia and May formula and increased application to turbulence intensity in weir downstream.
文摘The riprap air-cooled roadbed and common roadbed experimental project were designed and carried on in Qingshuihe test filed, an area of warm permafrost category with the fine frozen soil along Qinghai-Tibet Railway, to decide the temperature field of the roadbed after railway construction. Based on ground temperature variation of natural hole, left and right shoulder’s hole, the maximum thawing depth, and the deformation in these two kinds of roadbed were analysed comparatively. It showed that the riprap air-cooled roadbed had better effect of lowering ground temperature, lifting the maximum frozen-thawing depth obviously and decreasing deformation than that of the common roadbed. Therefore, the riprap air-cooled roadbed was a positive frozen soil protection measure for it effectively decreased ground temperature and protected permafrost.
基金financially supported by the Fundamental Research Funds for the Central Universities (Grant Nos.B200202087 and B200204032)the National Natural Science Foundation of China (Grant No.51609071)。
文摘Rubble mound breakwaters, a prevalent type of sloping breakwater structure, are extensively employed in port and coastal infrastructure projects. Under soft soil foundation conditions, the process of squeezing silt by riprap is implemented to enhance bearing capacity through soft soil replacement and compaction. However, predicting the depth law of squeezing silt by riprap and understanding its mechanism remain significant engineering design challenges.This study employs particle flow code(PFC) based on the discrete element method to simulate the squeezing silt process by riprap, examining variations in depth law under different geological conditions and its mechanical characteristics.Through calibration of the PFC model's meso-parameters via macro-experiments, the study analyzes the effects of riprap size, drop height, and soft soil properties on the depth law of squeezing silt. Findings demonstrate that riprap drop height and soft soil thickness substantially influence the depth, while appropriate calibration of meso-parameters enhances simulation accuracy. This research contributes theoretical and practical guidance for optimizing rubble mound breakwater design, understanding squeezing silt mechanisms, construction practices, and riprap quantity estimation.
