The erosion shape and the law of development of debris flow sabo dam downstream is a weak part in the study on debris flow erosion. The shape and development of scour pit have an important effect on the stability and ...The erosion shape and the law of development of debris flow sabo dam downstream is a weak part in the study on debris flow erosion. The shape and development of scour pit have an important effect on the stability and safety of debris flow sabo dam, which determines the foundational depth of the dam and the design of protective measures downstream. Study on the scouring law of sabo dam downstream can evaluate the erosion range and reasonably arrange auxiliary protective engineering. Therefore, a series of flume experiments are carried out including different debris flow characteristics （density is varying from 1.5 t/m3 to 2.1 t/m~） and different gully longitudinal slopes. The result shows that the scour pit appears as an oval shape in a plane and deep in the middle while superficial at the ends in the longitudinal section, the position of the maximum depth point moves towards downstream with an increase of flume slope angle. The maximum depth of scour pit is mainly affected by the longitudinal slope of gully, density of debris flow, and the characteristics of gully composition （particle size and the viscosity of soil）. The result also indicates that the viscosity of soil will weaken the erosion extent. The interior slopes of scour pit are different between the upstream and the downstream, and the downstream slope is smaller than the upper one. For the viscous and non-viscous sands with the same distribution of gradation, the interior slope of non- viscous sand is smaller than the viscous sand.According to tbe regression analysis on the experimental data, the quantitative relationship between the interior slope of scour pit, slope of repose under water and the longitudinal slope of gully is established and it can be used to calculate the interior slope of scour pit. The results can provide the basis for the parameter design of the debris flow control engineering foundation.展开更多
Recognizing the risk of fluvial bank erosion is an important challenge to ensure the early warning and prevention or control of bank collapse in river catchments,including in the Yangtze River.This study introduces a ...Recognizing the risk of fluvial bank erosion is an important challenge to ensure the early warning and prevention or control of bank collapse in river catchments,including in the Yangtze River.This study introduces a geomorphons-based algorithm to extract river bank erosion information by adjusting the flatness from multibeam echo-sounding data.The algorithm maps ten subaqueous morphological elements,including the slope,footslope,flat,ridge,peak,valley,pit,spur,hollow,and shoulder.Twentyone flatness values were used to build an interpretation strategy for the subaqueous features of riverbank erosion.The results show that the bank scarp,which is the erosion carrier,is covered by slope cells when the flatness is 10°.The scour pits and bank scars are indicated by pit cells near the bank and hollow cells in the bank slope at a flatness of 0°.Fluvial subaqueous dunes are considered an important factor accelerating bank erosion,particularly those near the bank toe;the critical flatness of the dunes was evaluated as 3°.The distribution of subaqueous morphological elements was analyzed and used to map the bank erosion inventory.The analysis results revealed that the near-bank zone,with a relatively large water depth,is prone to form large scour pits and a long bank scarp.Arc collapse tends to occur at the long bank scarp to shorten its length.The varied assignment of flatness values among terrestrial,marine,and fluvial environments is discussed,concluding that diversified flatness values significantly enable fluvial subaqueous morphology recognition.Consequently,this study provides a reference for the flatness-based recognition of fluvial morphological elements and enhances the targeting of subaqueous signs and risks of bank failure with a range of multibeam bathymetric data.展开更多
基金the National Natural Science Foundation of China (Nos. 40901007, 50979103)
文摘The erosion shape and the law of development of debris flow sabo dam downstream is a weak part in the study on debris flow erosion. The shape and development of scour pit have an important effect on the stability and safety of debris flow sabo dam, which determines the foundational depth of the dam and the design of protective measures downstream. Study on the scouring law of sabo dam downstream can evaluate the erosion range and reasonably arrange auxiliary protective engineering. Therefore, a series of flume experiments are carried out including different debris flow characteristics （density is varying from 1.5 t/m3 to 2.1 t/m~） and different gully longitudinal slopes. The result shows that the scour pit appears as an oval shape in a plane and deep in the middle while superficial at the ends in the longitudinal section, the position of the maximum depth point moves towards downstream with an increase of flume slope angle. The maximum depth of scour pit is mainly affected by the longitudinal slope of gully, density of debris flow, and the characteristics of gully composition （particle size and the viscosity of soil）. The result also indicates that the viscosity of soil will weaken the erosion extent. The interior slopes of scour pit are different between the upstream and the downstream, and the downstream slope is smaller than the upper one. For the viscous and non-viscous sands with the same distribution of gradation, the interior slope of non- viscous sand is smaller than the viscous sand.According to tbe regression analysis on the experimental data, the quantitative relationship between the interior slope of scour pit, slope of repose under water and the longitudinal slope of gully is established and it can be used to calculate the interior slope of scour pit. The results can provide the basis for the parameter design of the debris flow control engineering foundation.
基金This study was funded by the joint project supported by National Natural Science Foundation of China(NSFC)-Netherlands Organisation for Scientific Research(NWO)-Engineering and Physical Sciences Research Council(EPSRC)(51761135023)the China Geological Survey(DD20190260)NSFC(41476075).
文摘Recognizing the risk of fluvial bank erosion is an important challenge to ensure the early warning and prevention or control of bank collapse in river catchments,including in the Yangtze River.This study introduces a geomorphons-based algorithm to extract river bank erosion information by adjusting the flatness from multibeam echo-sounding data.The algorithm maps ten subaqueous morphological elements,including the slope,footslope,flat,ridge,peak,valley,pit,spur,hollow,and shoulder.Twentyone flatness values were used to build an interpretation strategy for the subaqueous features of riverbank erosion.The results show that the bank scarp,which is the erosion carrier,is covered by slope cells when the flatness is 10°.The scour pits and bank scars are indicated by pit cells near the bank and hollow cells in the bank slope at a flatness of 0°.Fluvial subaqueous dunes are considered an important factor accelerating bank erosion,particularly those near the bank toe;the critical flatness of the dunes was evaluated as 3°.The distribution of subaqueous morphological elements was analyzed and used to map the bank erosion inventory.The analysis results revealed that the near-bank zone,with a relatively large water depth,is prone to form large scour pits and a long bank scarp.Arc collapse tends to occur at the long bank scarp to shorten its length.The varied assignment of flatness values among terrestrial,marine,and fluvial environments is discussed,concluding that diversified flatness values significantly enable fluvial subaqueous morphology recognition.Consequently,this study provides a reference for the flatness-based recognition of fluvial morphological elements and enhances the targeting of subaqueous signs and risks of bank failure with a range of multibeam bathymetric data.
