Debris flow sand blocking dam attachment and size determination method
阅读说明：本技术 一种泥石流拦砂坝附属装置及尺寸确定方法 (Debris flow sand blocking dam attachment and size determination method ) 是由 谢湘平 王小军 鲍森 杨莉明 付裕 冯磊 于 2021-06-22 设计创作，主要内容包括：本发明涉及一种泥石流拦砂坝附属装置,属于山地灾害技术领域。该附属装置可持续分离山洪、泥石流粗颗粒,以最大程度地发挥拦砂坝的功能。该装置安置于已有拦砂坝下游,与拦砂坝溢流口连接,包括：正面斜格栅、正面水平格栅、侧面斜格栅和侧面水平格栅；本发明还提供了一种该装置修建尺寸的确定方法,针对不同的实际情况需确定装置的合理修建尺寸,使该装置具有良好的粗颗粒调控效果。(The invention relates to an auxiliary device for a debris flow sand dam, and belongs to the technical field of mountain disasters. The auxiliary device can continuously separate the mountain torrents and debris flow coarse particles so as to exert the function of the sand dam to the maximum extent. The device is settled and has had sand blocking dam low reaches, is connected with sand blocking dam overflow mouth, includes: the device comprises a front inclined grating, a front horizontal grating, a side inclined grating and a side horizontal grating; the invention also provides a method for determining the building size of the device, and the reasonable building size of the device needs to be determined according to different practical situations, so that the device has a good coarse particle regulation effect.)
1. An attachment for a debris flow dam, said attachment being disposed downstream of the dam and being connected to an overflow port of the dam, comprising: the device comprises a front inclined grating, a front horizontal grating, a side inclined grating, a side horizontal grating and a support pier; one end of the front inclined grating is connected with the overflow port of the sand blocking dam, the other end of the front inclined grating is connected with the front horizontal grating, and the position of the front horizontal grating is lower than the overflow port of the sand blocking dam; the side inclined gratings are symmetrically distributed on two sides of the front inclined grating, one ends of the two side inclined gratings are respectively connected with the end edges of two sides of the front inclined grating, and the other ends of the two side inclined gratings are connected with the side horizontal grating; and the front horizontal grating and the side horizontal grating are supported by the supporting piers to be higher than the dam bottom.
2. The attachment of claim 1, wherein the lateral horizontal grid is horizontally connected to the frontal horizontal grid.
3. The attachment of claim 1 wherein the angled side grilles have an angled downstream intersection angle of 45 ° to 60 ° with the angled front grilles.
4. The method for determining the size of an attachment of a debris flow dam according to claim 1 or 2, comprising the steps of:
the solid matter separation rate p value was determined according to the formula (1):
determining the grid spacing D according to equation (2):
D＝dp (2)
determining the front inclined grid gradient theta according to the formula (3)1：
Determining the height H of the front horizontal grid support pier according to the formulas (4) to (5)h：
Determining the vertical height H of the front inclined grid according to the formulas (6) to (7)sAnd length Ls：
Hs＝H-Hh (6)
Determining the front horizontal grid Length L according to equation (8)h1：
Determining the intersection angle beta of the side oblique grating and the front oblique grating according to the formula (9):
β＝90-θ1-α (9)
determining the slope theta of a side grating according to equation (10)2：
Determining the lateral horizontal grid length according to equation (11):
wherein:
γct: target volume weight, g/cm, after grid structure regulation3(ii) a The control objectives are assumed to be: the mud-rock flow is modified after being regulated and controlled by the grating, and the mud-rock flow with high volume weight is changed into the mud-rock flow or the water-rock flow with low volume weight, namely the volume weight gamma of the regulated and controlled target fluidctThe method comprises the following steps of (1) knowing;
d: grid spacing;
dp: the cumulative percentage of the particle size in the debris flow particle grading curve which is smaller than the particle size is the particle size value corresponding to p;
angle of repose of coarse particles;
Qc、Qc': flow rate m of debris flow before and after being regulated by the grating3/s；
γs: the volume weight of the solid matter can be generally 2.6 to 2.7g/cm3；
γc: the volume weight of the debris flow is g/cm before the grid structure is regulated and controlled3；
Cv: the solid matter concentration and the volume weight of the debris flow satisfy the relational expressionγwTaking the volume weight of water as 1.0g/cm3；
b: the width of an overflow port of the debris flow dam;
h: the total height of the overflow port of the sand blocking dam from the dam bottom;
vc: the designed flow velocity of the debris flow passing through the cross section of the overflow port;
vc': the flow velocity of the debris discharged to the downstream after being regulated and controlled by the grating, m/s, can be generally selected as vc'≈vc；
μ: the sliding friction coefficient between the coarse particles and the grating is determined according to the grating material;
g: acceleration of gravity;
θ1: a front side inclined grid slope;
Hh: the height of the front horizontal grid support pier;
Ls: the inclined length of the front inclined grating;
Lh1: front horizontal grid length;
α: the inclination angle of the downstream surface of the sand dam is generally 3-11 degrees;
θ2: side inclined grid slope;
b: width of debris flow channel.
Technical Field
The invention relates to a debris flow debris dam, in particular to an auxiliary device of the debris flow debris dam capable of separating floating trees and coarse particles and a method for determining the size of the auxiliary device, and belongs to the technical field of mountain disasters.
Background
The debris flow is a solid-liquid two-phase fluid full of silt and stones, which occurs in mountainous areas, usually has sudden and short outbreak, and has high solid-phase substance content, wide gradation and strong silt flushing capacity.
The dam is an important measure in debris flow prevention and control engineering and can be divided into a solid sand dam and an open grid dam according to structure and function. The solid sand dam has the main functions of completely or partially intercepting the incoming water and sand from the upstream, reducing the concentration of debris flow, changing the conditions of water and sand transportation and controlling the particle size of the discharged and sand transported; slowing down the slope fall of the riverbed, reducing the movement speed of debris flow and reducing the longitudinal erosion of the riverbed and the gravity erosion of two banks or transverse banks. The erosion datum plane of the local ditch bed is improved, the slope and valley stabilizing effect is achieved, and the type of the largest sand dam is built.
The debris flow grid dam can be divided into a beam grid dam, a steel pipe grid dam, a comb dam, a pile forest and the like according to the structural form. These grid dams have the same characteristics: the drainage holes with a certain size are arranged on the dam body, so that fine particles and debris flow slurry are allowed to penetrate through the blocking dam, and debris flow coarse particles are blocked in front of the dam in a sorting place, so that the content, the volume weight, the scale and the impact force of the debris flow coarse particles are reduced, and the purpose of reducing the damage of the debris flow is achieved.
The physical sand dam usually has a full reservoir capacity due to poor sorting property, so that it loses the function of continuously intercepting sediment. And a part of solid sand blocking dams form a bursting flood peak even after bursting, so that the damage of debris flow is increased.
The conventional debris flow grid dam (fig. 1(a)) has the defects that the blocked debris flow coarse particles are directly accumulated in the structure body to block the drainage hole (fig. 1(b)), so that the function of blocking the coarse particles and the fine particles cannot be continuously realized; secondly, the blocked open grid dam is similar to a solid dam, and the silt blocking function is lost even after the storage capacity is full.
Disclosure of Invention
The invention provides an auxiliary device of a debris flow debris dam capable of continuously separating debris particles from torrential flood and debris flow, aiming at solving the problem that the existing debris flow debris dam cannot well play the functions of intercepting silt, blocking thick and discharging thin after being full, so as to play the function of the existing debris dam to the maximum extent, and a novel debris dam with better functionality can be formed by combining conventional debris dams when the debris dam is newly built.
In order to achieve the above object, the present invention provides an attachment for a debris flow dam, which is an attachment for continuously separating floating wood and debris flow coarse particles on the basis of an existing debris flow dam, and is installed at the downstream of the existing debris flow dam and connected with an overflow port of the debris flow dam, and comprises: the device comprises a front inclined grating, a front horizontal grating, a side inclined grating, a side horizontal grating and a support pier; one end of the front inclined grating is connected with an overflow port of the sand blocking dam, and the front inclined grating has the functions of separating coarse particles and adjusting the concentration, volume weight, flow rate and the like of solid matters in the debris flow; the other end of the front inclined grid is connected with a front horizontal grid, the position of the front horizontal grid is lower than an overflow port of the sand blocking dam, and the front horizontal grid is used for stopping coarse particulate matters separated by the front inclined grid; the side inclined gratings are symmetrically distributed on two sides of the front inclined grating, one ends of the two side inclined gratings are respectively connected with the end edges of two sides of the front inclined grating, the other ends of the side inclined gratings are connected with the side horizontal grating, the side inclined gratings and the side horizontal grating are used for assisting in separating debris flow coarse particles falling from the front inclined gratings to two sides in a rolling mode, and a silt stopping space can be widened; and the front horizontal grating and the side horizontal grating are supported by the supporting piers to be higher than the dam bottom.
Further, the lateral horizontal grids are horizontally connected with the front horizontal grids.
Further, the oblique downstream intersection angle of the side oblique grids and the front oblique grids is 45-60 degrees.
The working principle of the device is as follows: when debris flow flows into the front inclined grating of the auxiliary device of the invention through the overflow port of the existing sand-blocking dam, fine particles with the particle size smaller than the spacing of the gratings and slurry parts vertically fall into the bottom of the trench and are discharged to the downstream, coarse particles with the particle size larger than the spacing of the gratings and floating wood roll to the front horizontal grating along the gratings, move on the front horizontal grating for a certain distance and then stop accumulating on the horizontal grating; when coarse particles and floating wood move on the front inclined grating, if part of mud-rock fluid rolls to two sides, the mud-rock fluid can continue to move along the side inclined grating, fine particles and slurry fall into the channel through the gap of the side inclined grating and are discharged to the downstream, and the coarse particles, the floating wood and the like with the particle size larger than the space between the side inclined gratings continue to move along the side inclined grating to the side horizontal grating and stop accumulating. By the device, the solid sand dam without the coarse blocking and fine discharging functions and the open type grid dam without the coarse blocking and fine discharging functions have the coarse blocking and fine discharging functions again, so that the debris flow disaster reduction effect can be better played.
In order to enable the device to have a good coarse particle regulation and control effect, and to determine the reasonable construction size of the device aiming at different practical situations, the invention also provides a size determination method of the auxiliary device, which realizes an ideal regulation and control effect with the lowest cost by more accurately calculating and controlling the construction size of the device, and the method comprises the following steps:
the design solid matter separation rate p was determined according to formula (1):
determining the grid spacing D according to equation (2):
D＝dp (2)
determining the front inclined grid gradient theta according to the formula (3)1：
Determining the height H of the front horizontal grid support pier according to the formulas (4) to (5)h：
Determining the vertical height H of the front inclined grid according to the formulas (6) to (7)sAnd length Ls：
Hs＝H-Hh (6)
Determining the front horizontal grid Length L according to equation (8)h1：
Determining the intersection angle beta of the side oblique grating and the front oblique grating according to the formula (9):
β＝90-θ1-α (9)
determining the slope theta of a side grating according to equation (10)2：
Length of side horizontal grid: the value can be directly against the side walls of two banks of the trench from the intersection point of the side inclined grating, and the value range is that for fully playing the function of silt stopping and optimizing the cost
Wherein:
γct: target volume weight, g/cm, after grid structure regulation3(ii) a Assuming regulatory objectives: the modification of the debris flow is realized after the regulation and control of the grid structure, and the debris flow with high volume weight is changed into the debris flow or the water stone with low volume weightFlow, i.e. the volume weight gamma of the target fluid after conditioningctThe method comprises the following steps of (1) knowing;
d: grid spacing;
dp: the cumulative percentage of the particle size in the debris flow particle grading curve which is smaller than the particle size is the particle size value corresponding to p;
angle of repose of coarse particles;
Qc、Qc': flow rate m of debris flow before and after being regulated by the grating3/s；
γs: the volume weight of the solid matter can be generally 2.6 to 2.7g/cm3；
γc: the volume weight of the debris flow is g/cm before the grid structure is regulated and controlled3；
Cv: the solid matter concentration and the volume weight of the debris flow satisfy the relational expressionγwTaking the volume weight of water as 1.0g/cm3；
b: the width of an overflow port of the debris flow dam;
h: the total height of the overflow port of the sand blocking dam from the dam bottom;
vc: the designed flow velocity of the debris flow passing through the cross section of the overflow port;
vc': the flow velocity of the debris discharged to the downstream after being regulated and controlled by the grating, m/s, can be generally selected as vc'≈vc；
μ: the sliding friction coefficient between the coarse particles and the grating is determined according to the grating material;
g: acceleration of gravity;
θ1: a front side inclined grid slope;
Hh: the height of the front horizontal grid support pier;
Ls: the inclined length of the front inclined grating;
Lh1: front horizontal grid length;
α: the inclination angle of the downstream surface of the sand dam is generally 3-11 degrees;
θ2: side inclined grid slope;
b: width of debris flow channel.
The invention has good social and economic benefits and engineering practice significance:
1. the invention has wide application range and can continuously exert the separation capability of coarse particles of the debris flow. The invention can be installed at the downstream of the existing sand blocking dam, so that the solid sand blocking dam which originally has no coarse blocking and fine discharging function and the open type grid dam which has lost the coarse blocking and fine discharging function have the coarse blocking and fine discharging function again, thereby better playing the disaster reduction effect of debris flow; and can be combined with a newly-built sand dam, so that the regulation and control capability of the sand dam on debris flow is greatly enhanced.
2. The invention can increase the silt stopping capacity of the debris flow. Stopping silt through the horizontal grids at the downstream and the two sides, namely, the drainage channel occupying the original debris flow channel is not squeezed, and the debris flow silt stopping space can be enlarged. And the silt stopping area is convenient to clean, and the silt stopping space can be repeatedly utilized. By the parameter determination method provided by the invention, the cost optimization can be realized while ideal debris flow regulation and control are obtained.
3. Model experiment research shows that the device has a good separation effect particularly on floating trees carried in debris flow, particularly on long floating trees with the ratio of the length of the floating trees to the width of the opening of the overflow port of the sand dam larger than 1.5, the separation effect reaches 60-80%, and the disaster effect of the floating trees can be effectively reduced.
4. The invention has the function of protecting the dam site of the existing sand dam. Due to the inclined grilles on the front side and the two sides, coarse particles passing through the dam cannot directly fall behind the dam, and therefore the capability of debris flow for undercutting the dam site can be reduced.
5. The invention can realize the assembly type construction, and has convenient installation and strong operability.
Drawings
FIG. 1 shows an open type debris flow grid dam before (a) and after (b) being plugged with debris flow solid particles;
FIG. 2 is a top view of the attachment of the present invention;
FIG. 3 is a front view of the attachment of the present invention;
FIG. 4 is a side view of the attachment of the present invention;
wherein: 1: a sand blocking dam, 2: front inclined grid, 3: side inclined grid, 4: front horizontal grid, 5: lateral horizontal grid, 6: and (4) supporting piers.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
The invention provides an auxiliary device of a debris flow sand dam, the structure of which is shown in figures 2-4, the device is arranged at the downstream of the existing sand dam 1 and is connected with an overflow port of the sand dam, and the auxiliary device comprises: a front inclined grate 2, a front horizontal grate 4, a side inclined grate 3, a side horizontal grate 5 and a support pier 6.
The upward end of the front inclined grating is connected with the overflow port of the sand blocking dam, for example, the upward end of the front inclined grating is abutted against and fixed at the overflow port of the sand blocking dam, the downward other end of the front inclined grating is connected with the front horizontal grating, and the position of the front horizontal grating is lower than the overflow port of the sand blocking dam and is used for stopping silt from rolling off the separated coarse particulate matters from the front inclined grating; the side inclined gratings are symmetrically distributed on the left side and the right side of the front inclined grating, one ends of the two side inclined gratings are respectively connected with the left side end edge and the right side end edge of the front inclined grating, the other ends of the side inclined gratings are connected with corresponding side horizontal gratings, the side inclined gratings and the side horizontal gratings are used for assisting in separating debris flow coarse particles falling from the front inclined gratings to the two sides in a rolling mode, and a silt stopping space can be widened; the front horizontal grids and the side horizontal grids are supported by supporting piers to be higher than the dam bottom, so that fine particle substances separated by the grid gaps fall down.
The lateral horizontal grids are horizontally connected with the front horizontal grids, and the oblique downstream intersection angle of the lateral inclined grids and the front inclined grids is 45-60 degrees.
Example 2
The method for determining the size of the auxiliary device of the debris flow dam comprises the following steps: firstly, the following design parameters are obtained through field geological survey and experiment:
the width B of the channel is 20m, the height H from the bottom of the debris flow debris dam to the overflow port is 12m, the downstream gradient alpha of the debris flow debris dam is 10 degrees, and the width B of the overflow port is 10 m; design flow velocity v of debris flow design sectioncThe design flow Q is 8m/sc＝300m3S, initial volume weight of debris flow gammacIs 1.8g/cm3Solid matter concentration Cv0.47, angle of repose of coarse particles of solid material in debris flowAt 35 deg.C, the particle size distribution data of the solid matter in the debris flow is shown in Table 1 below, and the solid matter volume weight γsThe value is 2.65g/cm3The steel material is adopted to build the grid, and the sliding friction coefficient mu is 0.47.
Table 1 mud-rock flow solid matter particle full gradation data
The determination of the parameters of the accessory device is as follows:
regulating and controlling the target: after the device is regulated and controlled, the debris flow is changed into sand-containing water flow, and the volume weight gamma of the target fluidct＝1.45g/cm3。
(1) Determination of designed solid matter separation ratio p
(2) Grid spacing D
The spacing of the grid openings can be d according to the design solid matter separation rate p60According to the grading data of solid matter particles in the debris flow, the method comprises the following steps:
D＝d60＝100mm＝0.1m
(2) front inclined grid slope theta1
The slope of the front slanted grid affects the particles at itSpeed of upward movement and jamming, slope of front inclined grid theta1The following values are taken:
(3) height H of front horizontal grid support pierh
According to known conditions and the formulas (4) to (5), the following formula is calculated:
(4) vertical height H of front inclined gridsAnd length Ls
According to the known conditions and the formulas (6) and (7), the vertical height H of the front inclined gratingsAnd length LsRespectively as follows:
Hs＝12-2.7＝9.3m
(5) front horizontal grid length Lh1
According to the known conditions and the formula (8), the front horizontal grid length L can be calculatedh1：
Lh1＝16.7m
(6) Intersection angle beta of side oblique grating and front oblique grating
According to the known conditions and the formula (9), the intersection angle β of the side oblique grating and the front oblique grating takes the value:
β＝90-10-35＝45°
(7) slope theta of side inclined grid2
According to known conditions and formula (10):
meanwhile, a certain silt stopping space reserved for the horizontal grating on the side surface is considered, theta2The value is 70 degrees.
(8) Length of side horizontal grid
According to known conditions, the value varies within a range of
Therefore, the length of the horizontal grid on the side surface is 1.62-5 m.
The side horizontal grids and the front horizontal grids are built on the same plane.