CN107133434B - A Calculation Method of Critical Volume Concentration of Debris Flow - Google Patents
A Calculation Method of Critical Volume Concentration of Debris Flow Download PDFInfo
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Abstract
本发明公开了一种泥石流临界体积浓度的计算方法，该方法通过震区泥石流沟的野外调查手段，确定震区泥石流沟的泥石流固体容重γS，水体的容重γW，泥石流沟道坡度α，泥石流沟道纵比降J，泥石流沟道糙率系数n，泥石流沟道堆积物的内摩擦角θ，泥石流流深H，泥石流的粘滞系数η；将所获得的参数带入计算公式，可以获得泥石流起动过程的泥石流临界体积浓度，该方法适用于震区泥石流体积浓度预测。与现有技术相比，本发明基于严密的理论推导，能更准确的得到震区泥石流体积浓度的变化情况，为震区泥石流防治工程的设计提供依据，其运用简单、高效，可满足地质灾害预防需要。
The invention discloses a method for calculating the critical volume concentration of debris flow. The method determines the solid bulk density γ S of the debris flow in the debris flow trench in the earthquake region, the bulk density γ W of the water body, and the slope α of the debris flow channel by means of field investigation of debris flow trenches in the earthquake region. The vertical ratio drop of the debris flow channel J, the roughness coefficient n of the debris flow channel, the internal friction angle θ of the debris flow channel sediment, the debris flow depth H, and the viscosity coefficient η of the debris flow; the obtained parameters are brought into the calculation formula, you can The critical volume concentration of debris flow in the starting process of debris flow is obtained. This method is suitable for predicting the volume concentration of debris flow in the earthquake area. Compared with the prior art, the present invention is based on strict theoretical derivation, can more accurately obtain the variation of the volume concentration of debris flow in the earthquake area, provides a basis for the design of the debris flow prevention and control project in the earthquake area, and is simple and efficient to use, and can meet the requirements of geological disasters. Prevention needs.
Description
Technical Field
The invention belongs to the technical field of debris flow prevention engineering design application, and particularly relates to a method for calculating the critical volume concentration of a debris flow.
Background
The debris flow mainly comprises a water body, solid particles and other solid and liquid phases, namely the volume concentration of the debris flow is mainly determined by the content percentage of the solid particles in the debris flow and the grading of the solid particles, and the maximum solid particle calculation formula for the start of the silt and the volume-weight relationship between the volume concentration and the debris flow are calculated when the volume concentration C of the debris flow is greater than the limit volume concentration CCWhen this happens, the debris flow erodes the channel deposits. Therefore, the volume concentration characteristics of the debris flow in the strong earthquake areas are the key points of the research on the prevention and treatment of the debris flow.
The volume concentration change characteristics of the debris flow are related to factors such as longitudinal gradient of the channel, flow speed of the debris flow, roughness of the channel and the like. The debris flow volume concentration reflects not only the solid matter erosion characteristics during debris flow initiation, but also the fluid properties of surface runoff of erosion initiation debris flow channel accumulations. The volume concentration of the mud-rock flow is also mudThe table-needle parameter of the volume weight of the debris flow and one of the main parameters of the dynamic property of the debris flow. The volume concentration of the debris flow at any flow depth is different, and the volume concentration of the debris flow has a continuous function relation with the flow depth and the flow speed of the debris flow. For example, in the extra-large rainstorm period of '7.10' in 2013, 3 debris flows occur in the 3 channels of the debris flow on the mountain slope after the group 1 sheep shop, the volume concentration of the debris flow in the outbreak process is respectively 58% and 43.6% through a field matching method and a table look-up method, and the volume concentration of the debris flow in the outbreak process is about 41.2% through the percentage content of sticky particles and the percentage content of coarse particles. The cattle pen ditches are subjected to large-scale debris flow during the flood disasters of 9 and 26 in 2008 and 8 and 14 in 2010, wherein the amount of eroded sources is 17.15 multiplied by 104m3And 14.87X 104m3The loose solid matter source of the mud-rock flow in the cowshed ditch mainly comprises broken stones, the volume concentration of the mud-rock flow in the outbreak process is 47.3% by a field preparation method, and the volume concentration of the mud-rock flow in the outbreak process is about 38.8% by the percentage content of the sticky particles and the percentage content of the coarse particles.
The volume concentration of the debris flow reflects the physical characteristics of the debris flow fluid, and the solid particle content of the debris flow reflects the fluid concentration of the debris flow in the starting and outbreak processes; the volume concentration of the existing debris flow is mainly obtained through indoor experiments and field sampling, and the key point is to research the percentage content characteristics of solid particles of the debris flow in the debris flow. The critical volume concentration model based on debris flow channel section parameters and debris flow channel deposit physical properties can quickly acquire volume concentration parameters, and debris flow prevention and control in earthquake areas can be efficiently and conveniently popularized to design units and production units.
Disclosure of Invention
The invention aims to: aiming at the existing problems, the method for calculating the critical volume concentration of the debris flow is provided, the relation between the longitudinal channel drop and the debris flow depth and the critical volume concentration of the debris flow in the starting process of debris flow channel accumulation in the severe earthquake area is solved, a debris flow critical volume concentration prediction model based on the debris flow depth and the physical properties of the channel accumulation is constructed, and example application is carried out, so that a new method is provided for preventing and controlling the debris flow in the earthquake area, and the method is suitable for the requirements of actual engineering for preventing and controlling the debris flow.
The technical scheme of the invention has the implementation mode that: a method for calculating the critical volume concentration of a debris flow is characterized by comprising the following steps: the channel characteristics of the debris flow in the seismic region and the physical properties of debris flow channel accumulation are applied to the critical volume concentration prediction in the debris flow starting process in the seismic region, and the specific calculation method is as follows:
A. determining the channel gradient α of the debris flow channel, the longitudinal gradient J of the debris flow channel and the volume weight gamma of debris in the debris flow channel by acquiring the parameters of the debris flow channel in the seismic regionSVolume weight of water in mud-rock fluid gammaWThe internal friction angle theta of debris flow channel accumulation, the debris flow depth H, the roughness coefficient n of the debris flow channel and the viscosity coefficient η of the debris flow;
B. the critical volume concentration at the start of the debris flow in the seismic region is determined by the following formula,
in the formula, α is the channel gradient (°) of the debris flow channel, J is the longitudinal gradient ([ permi ]) of the debris flow channel, and gammaSFor debris flow channel deposit bulk density (KN/m)3)，γWIs the volume weight (KN/m) of water in the mud-rock fluid3) Theta is the internal friction angle (°) of debris flow channel deposit, H is debris flow depth (m), n is the roughness coefficient of the debris flow channel, η is the viscosity coefficient (Pa · s) of the debris flow, and the theta, the n and the η are determined in the step A.
According to the method for calculating the critical volume concentration of the debris flow, the formula for determining the critical volume concentration when the debris flow in the earthquake region is started in the step B is suitable for predicting the critical volume concentration in the starting process of the debris flow in the earthquake region, and the obtained debris flow volume concentration is used as the minimum debris flow volume concentration parameter for preventing and controlling the debris flow in the earthquake region.
Compared with the prior art, the invention has the beneficial effects that: the debris flow volume concentration calculation model based on debris flow channel parameters is constructed by breaking through the limitation of traditional experience and starting from the aspects of debris flow channel longitudinal gradient, debris flow channel width and the like. Firstly, in the aspect of longitudinal gradient of a debris flow channel, the longitudinal gradient change of the debris flow channel in the seismic area is fully considered, and the topographic gradient characteristic of the debris flow in the seismic area is quantitatively reflected by utilizing the longitudinal gradient change characteristic of the debris flow channel; secondly, based on the physical properties of debris flow channel deposits in Wenchuan earthquake areas, the mutual relation between the critical volume concentration and the cross section of the channel when the debris flow channel deposits in the earthquake areas are started is reflected according to the stress balance equation of debris flow fluid, the calculation theory is perfect, the calculation result accords with debris flow field investigation, and the technical support can be provided for debris flow prevention and control in the earthquake areas.
Drawings
Fig. 1 is a schematic diagram of a debris flow channel accumulation stress analysis.
The numbers in the figure are that △ H is the random erosion thickness of the channel accumulation, △ l is the random erosion length of the accumulation, H is the accumulation thickness of the debris flow, H is the depth of the debris flow, α is the gradient of the debris flow channel, dN is the supporting stress borne by the accumulation, and dGYIs the dead weight stress of the solid particles of the debris flow, dτThe stack is subjected to shear stress.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following description of the present invention with reference to the accompanying drawings and embodiments will be made in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
A method for calculating the critical volume concentration of a debris flow mainly comprises the following steps: the trench characteristics of the seismographic debris flow and the physical properties of debris flow trench accumulation are applied to the critical volume concentration prediction of the seismographic debris flow starting process. Firstly, deducing the debris flow depth when the debris flow moves according to the stress characteristics of debris flow channel accumulation; then determining the debris flow depth, the channel gradient, the channel longitudinal gradient, the debris flow channel roughness coefficient and the debris flow channel accumulation internal friction angle through means of investigation of the debris flow channel which is exposed in the earthquake area, measurement of characteristic parameters of the debris flow channel and the like; and substituting the obtained parameters into a computation model of the critical volume concentration of the debris flow in the seismic area to obtain a predicted value of the volume concentration when the debris flow channel accumulation is started.
The specific calculation method comprises the following steps:
assuming that the longitudinal ratio of the debris flow channel in the earthquake area is reduced to J, the gradient of the channel is α, the depth of the debris flow is H, the internal friction angle theta of the debris flow channel accumulation, the viscosity coefficient η of the debris flow and the volume weight gamma of the debris flow channel accumulation during starting are all equalSVolume weight of water in mud-rock fluid gammaW. The formula of the dead weight stress, the floating stress and the viscous force applied to the solid particles of the debris flow is expressed as the critical condition of the flow depth starting of the debris flow based on the seismic region, and the different erosion thicknesses of the debris flow are closely related to the flow depth of the debris flow. The stress balance formula when the debris flow channel accumulation in the earthquake region is started is expressed as follows:
wherein α is the channel gradient (°) of the debris flow channel, and γ is the bulk density (KN/m) of the debris flow channel deposit3)，γWIs the volume weight (KN/m) of water in the mud-rock fluid3) The saturation volume weight of the debris flow is gammasat(KN/m3) Theta is the internal friction angle (°) of debris flow channel deposit, H is debris flow depth (m), n is the roughness coefficient of the debris flow channel, η is the viscosity coefficient (Pa · s) of the debris flow, and J is the longitudinal gradient ([ thousandth ]) of the debris flow channel.
Then, since the channel gradient of the debris flow and the internal friction angle of the debris flow source are both constant values, the formula of the volume concentration when the debris flow starts in the seismic region is expressed as:
in the formula, the symbols are as shown above.
And B, determining the critical volume concentration of the earthquake region debris flow during starting in the step B, wherein the formula is suitable for predicting the critical volume concentration of the earthquake region debris flow during starting, and the obtained debris flow volume concentration is used as the minimum debris flow volume concentration parameter for preventing and controlling the earthquake region debris flow.
The following are specific examples of the present invention:
the catchment area of the small sentry sword drainage basin is 0.61km2The longitudinal ratio of the channel forming the circulation area is reduced to 506 per thousand. According to the watershed remote sensing analysis of the small sentry sword debris flow channel, the overall slope of the watershed is more than 30 degrees on the average slope and more than 50 degrees locally. The slope of the debris flow channel is more than 30 degrees on average, and the slope of the downstream steep bank of the debris flow flowing area is more than 50 degrees.
In order to effectively prevent and treat the debris flow and prevent the long-distance river from being blocked to threaten the downstream safety, effective prediction is carried out according to the characteristics of debris flow channels, designed widths of sand dams and the like, and the specific calculation method and the steps are as follows:
A. according to field investigation and debris flow channel parameter test of the small sentry sword debris flow channel, the average debris depth of the 1# sand blocking dam of the small sentry sword channel is determined to be 0.73m, and the solid volume weight of accumulated debris of the debris flow channel is 26.6 (KN/m)3) Viscosity coefficient is 1.005 (Pa.s), debris flow longitudinal ratio is decreased by 483 ‰, roughness coefficient is 12, and internal friction angle of debris flow channel accumulation is 33 deg.
B. Substituting the parameters determined in the step A into the following formula,
C. the critical volume concentration of 3.9% in the debris flow channel accumulation starting process is obtained through formula calculation, and then the volume concentration of 3.9% in the debris flow channel accumulation starting process at the small post Jian debris flow No. 1 sand control dam prevention and control project position is obtained.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (2)
1. A method for calculating the critical volume concentration of a debris flow is characterized by comprising the following steps: the method applies the channel characteristics of the debris flow in the seismic region and the physical properties of debris flow channel accumulation to the critical volume concentration prediction in the debris flow starting process in the seismic region, and comprises the following specific calculation steps:
A. determining the channel gradient α of the debris flow channel, the longitudinal gradient J of the debris flow channel and the volume weight gamma of debris in the debris flow channel by acquiring the parameters of the debris flow channel in the seismic regionSVolume weight of water in mud-rock fluid gammaWThe internal friction angle theta of debris flow channel accumulation, the debris flow depth H, the roughness coefficient n of the debris flow channel and the viscosity coefficient η of the debris flow;
B. the critical volume concentration at the start of the debris flow in the seismic region is determined by the following formula,
wherein α is the channel gradient of the debris flow channel, and J is the longitudinal gradient of the debris flow channel, and the unit ‰, γSThe unit of KN/m is the volume weight of debris flow channel accumulation3，γWIs the volume weight of water in the mud-rock fluid and has a unit of KN/m3Theta is the internal friction angle of debris flow channel accumulation, unit degree, H is debris flow depth, unit m, n is the roughness coefficient of the debris flow channel, η is the viscosity coefficient of the debris flow, unit Pa & s are determined by the step A.
2. The method for calculating the critical volume concentration of a debris flow according to claim 1, wherein: and B, determining a formula of the critical volume concentration when the debris flow in the earthquake region is started in the step B, wherein the formula is suitable for predicting the critical volume concentration in the debris flow starting process in the earthquake region, and the obtained debris flow volume concentration is used as the minimum debris flow volume concentration parameter for preventing and controlling the debris flow in the earthquake region.
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| CN107391924B (en) * | 2017-07-19 | 2020-08-04 | 四川建筑职业技术学院 | A method for calculating the bulk density of debris flow in seismic area based on particle size parameters of debris flow source |
| CN108021764B (en) * | 2017-12-15 | 2021-05-07 | 四川建筑职业技术学院 | Method for calculating starting flow depth of glacier debris flow |
| CN110147394B (en) * | 2019-05-25 | 2022-06-21 | 成都理工大学 | Statistical method-based method for predicting hundred-year siltation depth of debris flow |
| CN110472183B (en) * | 2019-08-21 | 2022-04-05 | 中国地质科学院探矿工艺研究所 | Debris flow volume weight calculation method based on disaster spatiotemporal evolution |
| CN110532683B (en) * | 2019-08-28 | 2023-03-10 | 四川建筑职业技术学院 | A Calculation Method of Debris Flow Bulk Density Based on Channel Flow Depth and Compressive Stress |
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