Debris flow drainage channel with step pool structure and its applications

Abstract

A debris flow drainage channel is provided. The debris flow drainage channel is applicable to debris flows with large gully bed longitudinal slopes. The debris flow drainage channel has an upstream step section and a downstream step section. The debris flow drainage channel also has a step pool disposed between the upstream step section and the downstream step section. The pool section has a cable net cage bottom protection, a cable net cage buffer layer and block stones.

Claims

1. A debris flow drainage channel comprising: a drainage channel bottom and drainage channel side walls arranged on both sides of the drainage channel bottom, wherein the drainage channel bottom comprises: at least one upstream step section and at least one downstream step section, wherein the at least one upstream step section and the at least one downstream section are fully lined and distanced from each other by a predetermined interval, and wherein each step section comprises an upper vertical wall located upstream, a lower vertical wall located downstream and a fully lined baseplate connecting the upper vertical wall and the lower vertical wall; and at least one pool section disposed between the at least one upstream step section and the at least one downstream step section, wherein the at least one pool section comprises: a cable net cage bottom protection, a cable net cage buffer layer and block stones, wherein the cable net cage buffer layer is disposed above the cable net cage bottom protection and abuts the upper vertical wall of the at least one downstream step section; and wherein the block stones are disposed in a space defined by the drainage channel side walls, the cable net cage bottom protection, the lower vertical wall of the at least one upstream step section and the cable net cage buffer layer; wherein the cable net cage bottom protection and the cable net cage buffer layer are formed by wrapping additional block stones in a cable net, wherein the at least one pool section has a top surface that is flush with the highest point of the at least one downstream step section, wherein the at least one upstream step section and the at least one downstream step section have a step section length, and the at least one pool section has a length that is smaller than the step section length, wherein the length of the at least one pool section is equal to the sum of a laying length of the block stones and a thickness of the cable net cage buffer layer, wherein a length of the cable net cage bottom protection is equal to the length of the at least one pool section, wherein a height of the upper vertical wall is equal to the sum of a laying thickness of the block stones and a thickness of the cable net cage bottom protection, wherein a height of the cable net cage buffer layer is equal to the laying thickness of the block stones, wherein the length of the at least one pool section is greater than or equal to a quarter of the step section length and less than or equal to half of the step section length, wherein a height of the lower vertical wall is equal to the sum of a suspension height of the lower vertical wall, the laying thickness of the block stones, the thickness of the cable net cage bottom protection and an extra-buried depth of the lower vertical wall, wherein the suspension height of the lower vertical wall is less than or equal to 3.0 m, wherein the suspension height (h.sub.11) of the lower vertical wall is calculated based on the equation: h.sub.11=(L.sub.1+L.sub.4)×i.sub.0−L.sub.1×i.sub.1, wherein L.sub.1 refers to the step section length; L.sub.4 refers to the length of the at least one pool section; i.sub.0 refers to an average gully bed longitudinal slope, which is set as 0.2-0.4; and i.sub.1 refers to a slope of the at least one upstream step section and the at least one downstream step section, and wherein the extra-buried depth of the lower vertical wall is 0.5-1.0 m.

2. The debris flow drainage channel according to claim 1, wherein the laying length of the block stones is 2.0-4.0 m; wherein the laying thickness of the block stones is 1.0-2.0 m; and wherein a particle size of the block stones is 0.2-0.5 m.

3. The debris flow drainage channel according to claim 1, wherein the thickness of the cable net cage bottom protection is 0.5-1.0 m; wherein the thickness of the cable net cage buffer layer is 0.5-1.0 m; wherein a mesh size of cable nets of the cable net cage bottom protection and the cable net cage buffer layer is set as (0.1 m×0.1 m)−(0.2 m×0.2 m); and wherein the cable diameter of the cable nets of the cable net cage bottom protection and the cable net cage buffer layer is 0.005-0.01 m.

4. The debris flow drainage channel according to claim 1, wherein the slope of the at least one upstream step section and the at least one downstream step section is 0.08-0.15, and the step section length is 5.0-20.0 m.

5. The debris flow drainage channel according to claim 1, wherein the baseplate comprises a cement-laid stone masonry structure, a concrete structure or a reinforced concrete structure; wherein a thickness of the base plate is 0.5-1.0 m; and wherein the ratio between a width of the drainage channel bottom and a depth of the drainage channel is greater than or equal to 2.0.

6. The debris flow drainage channel according to claim 1, wherein the drainage channel is applicable to drain debris flows that have an average gully bed longitudinal slope of 0.2-0.4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic top view of the debris flow drainage channel with a step pool structure.

(2) FIG. 2 is a diagrammatic drawing of the longitudinal section of a side face of the debris flow drainage channel with a step pool structure.

(3) FIG. 3 is a diagrammatic drawing of the longitudinal section of a channel center of the debris flow drainage channel with a step pool structure.

(4) FIG. 4 is an enlarged diagrammatic drawing of the longitudinal section of the channel center of the debris flow drainage channel with a step pool structure.

(5) FIG. 5 is a diagrammatic drawing of the cross section of the pool section of the debris flow drainage channel with a step pool structure.

(6) FIG. 6 is a diagrammatic drawing of the cross section of the step section of the debris flow drainage channel with a step pool structure.

(7) Labels in the figures are as follows:

(8) TABLE-US-00001 1 side wall 2 step section 3 upper indented sill 4 lower indented sill 5 baseplate 6 cable net cage bottom protection 7 cable net cage buffer layer 8 block stone i.sub.1 slope of step section i.sub.0 average gully bed longitudinal slope L.sub.1 length of step section L.sub.2 laying length of block stones L.sub.3 thickness of cable net cage buffer layer L.sub.4 length of pool section h.sub.1 height of lower indented sill h.sub.11 suspension height h.sub.12 laying thickness of block stones h.sub.13 thickness of cable net cage bottom protection h.sub.14 extra-buried depth h.sub.2 height of upper indented sill B width of channel bottom H depth of drainage channel

DESCRIPTION OF THE EMBODIMENTS

(9) The following further describes the main embodiments of the invention with reference to the accompanying drawings.

Embodiment 1

(10) As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6, when the area of the drainage basin of some debris flow gully is 1.78 km.sup.2, to prevent debris flow disasters, one silt arrester is designed to be placed in the middle of the drainage basin, and a drainage channel with a length of 240 m is designed to be built on a deposition fan. For the drainage channel, the average gully bed longitudinal slope i.sub.0 of the channel bottom is 0.40, the flow rate of the drained debris flow is 96 m.sup.3/s, and the density is 21.5 kN/m.sup.3, to control the intense abrasion and scouring actions of the debris flow, the debris flow drainage channel with a step-pool structure is adopted. The debris flow drainage channel with a step pool structure consists of a drainage channel bottom and drainage channel side walls (1) arranged on both sides of the drainage channel bottom, wherein the drainage channel bottom consists of multiple fully lined step sections. Two sections are arranged at a given interval, and a pool section is filled between every adjacent upstream and downstream step sections (2). The step section (2) consists of an upper indented sill (3) located upstream, a lower indented sill (4) located downstream and a fully lined baseplate (5) connecting the upper indented sill (3) with the lower indented sill (4). The pool section consists of a cable net cage bottom protection (6), a cable net cage buffer layer (7) and block stones (8). The cable net cage buffer layer is arranged above the cable net cage bottom protection (6) and clung to the upper indented sill (3) of the downstream step section (2), and the block stones are arranged in a space defined by the side walls (1), the cable net cage bottom protection (6), the lower indented sill (4) of the upstream step section (2) and the cable net cage buffer layer (7). The cable net cage bottom protection (6) and the cable net cage buffer layer (7) are formed by wrapping block stones in a cable net; the top surface of the pool section is flush with the highest point of the downstream step section (2).

(11) According to the given conditions (i.e., the flow rate of drained debris flow is 96 m.sup.3/s, the average gully bed longitudinal slope i.sub.0 of the channel bottom is 0.40, and the density is 21.5 kN/m.sup.3) of the debris flow area, the width B of the drainage channel bottom being 8.0 m and the depth H of the drainage channel being 2.5 m are planned and designed.

(12) A laying length L.sub.2 of the block stones of 2.0 m, a laying thickness h.sub.12 of the block stones (8) of 2.0 m, a thickness L.sub.3 of the cable net cage buffer layer (7) of 1.0 m, and a particle size of block stones laid in the pool of 0.5 m are determined according to the density of the debris flow, and the length L.sub.4 of the pool section is 3.0 m (i.e., L.sub.2+L.sub.3).

(13) The fully lined baseplate (5), which has a thickness of 1.0 m, is composed of a reinforced concrete structure. The slope i.sub.1 of the step section (2) is 0.15, determined according to the abrasion resistance of materials constituting the fully lined baseplate (5). The length L.sub.1 of the step section (2) is designed mainly according to the average gully bed longitudinal slope i.sub.0 and the materials constituting the fully lined baseplate (5) and is taken as 6.0 m, which satisfies the condition L.sub.1/4≦L.sub.4≦L.sub.1/2. Thus, the suspension height h.sub.11 of the lower indented sill (4) is 2.7 m, which is obtained using (L.sub.1+L.sub.4)×i.sub.0−L.sub.1×i.sub.1=(L.sub.1+L.sub.2+L.sub.3)×i.sub.0−L.sub.1×i.sub.1=(6.0+2.0+1.0)×0.40−6.0×0.15.

(14) According to the density of the debris flow and the suspension height h.sub.11 of the lower indented sill (4), the thickness h.sub.13 of the cable net cage bottom protection (6) is 1.0 m, the cable diameter of the cable net cage bottom protection (6) and the cable net cage buffer layer (7) is 0.01 m, and the mesh size of the cable net is 0.2 m×0.2 m. Finally, the extra-buried depth h.sub.14 of the lower indented sill (4) is 1.0 m.

(15) The height h.sub.1 of the lower indented sill (4) is 6.7 m (i.e., h.sub.11+h.sub.12+h.sub.13+h.sub.14=2.7+2.0+1.0+1.0), and the height h.sub.2 of the upper indented sill (3) is 3.0 m (i.e., h.sub.12+h.sub.13=2.0+1.0).

(16) Summarizing, the key parameters of the debris flow drainage channel with a step pool structure are as follows: the average gully bed longitudinal slope i.sub.0 of the channel bottom is 0.40, the width B of the drainage channel bottom is 8.0 m, and the depth H of the drainage channel is 2.5 m. The slope i.sub.1 of the step section (2) is 0.15, the length L.sub.1 of the step section (2) is 6.0 m, h.sub.2 of the upper indented sill (3) is 3.0 m, and the height h.sub.1 of the lower indented sill (4) is 6.7 m. In addition, the fully lined baseplate (5) consists of a reinforced concrete structure, with a thickness of 1.0 m. For the pool section, the laying length L.sub.2 of the block stones (8) is 2.0 m, the laying thickness h.sub.12 of the block stones (8) is 2.0 m, the particle size of the block stones (8) is 0.5 m, the thickness L.sub.3 of the cable net cage buffer layer (7) is 1.0 m, the height of the cable net cage buffer layer (7) is 2.0 m, the thickness h.sub.13 of the cable net cage bottom protection (6) is 1.0 m, the length of the cable net cage bottom protection (6) is 3.0 m, the cable diameter of the cable net cage bottom protection (6) and of the cable net cage buffer layer (7) is 0.01 m, the mesh size of the cable net is 0.2 m*0.2 m, and the suspension height h.sub.11 of the lower indented sill (4) is 2.7 m.

Embodiment 2

(17) As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6, when the area of the drainage basin of a given debris flow gully is 8.6 km.sup.2, to prevent debris flow disasters, three silt arresters are designed to be arranged in the middle of the drainage basin, and a drainage channel with a length of 480 m is designed to be built on a deposition fan. For the drainage channel, the average gully bed longitudinal slope i.sub.0 of the channel bottom is 0.20, the flow rate of the drained debris flow is 265 m.sup.3/s, and the density is 15 kN/m.sup.3, to control the intense abrasion and scouring actions of the debris flow, and the debris flow drainage channel with a step pool structure is adopted. The debris flow drainage channel with a step pool structure consists of a drainage channel bottom and drainage channel side walls (1) arranged on both sides of the drainage channel bottom, wherein the drainage channel bottom consists of multiple fully lined step sections (2) arranged at a given interval and a pool section filled between every adjacent upstream and downstream step sections (2). Each step section (2) consists of an upper indented sill (3) located upstream, a lower indented sill (4) located downstream, and a fully lined baseplate (5) connecting the upper indented sill (3) with the lower indented sill (4). The pool section consists of a cable net cage bottom protection (6), a cable net cage buffer layer (7) and block stones (8). The cable net cage buffer layer is arranged above the cable net cage bottom protection (6) and clung to the upper indented sill (3) of the downstream step section (2), and the block stones are arranged in a space defined by the side walls (1), the cable net cage bottom protection (6), the lower indented sill (4) of the upstream step section (2) and the cable net cage buffer layer (7). The cable net cage bottom protection (6) and the cable net cage buffer layer (7) are formed by wrapping block stones in a cable net. In addition, the top surface of the pool section is flush with the highest point of the downstream step section (2).

(18) According to the given conditions (i.e., the flow rate of the drained debris flow is 265 m.sup.3/s, the average gully bed longitudinal slope i.sub.0 of the channel bottom is 0.20, and the density is 15 kN/m.sup.3) of the debris flow area, a width B of the drainage channel bottom of 10.0 m and a depth H of the drainage channel of 5.0 m are planned and designed.

(19) According to the density of the debris flow, the laying length L.sub.2 of the block stones is 4.0 m, the laying thickness h.sub.12 of the block stones (8) is 1.0 m, the thickness L.sub.3 of the cable net cage buffer layer (7) is 0.5 m, and the particle size of the block stones laid in the pool is 0.2 m. In addition, the length L.sub.4 of the pool section is 4.5 m (i.e., L.sub.2+L.sub.3).

(20) The fully lined baseplate (5) is a cement-laid stone masonry structure, and the thickness is 0.5 m. The slope i.sub.1 of the step section (2) is 0.08, as determined according to the abrasion resistance of materials composing the fully lined baseplate (5). The length L.sub.1 of the step section (2) is planned mainly according to the average gully bed longitudinal slope i.sub.0 and the materials of the fully lined baseplate (5), therein taking on a value of 18.0 m. The suspension height h.sub.11 of the lower indented sill (4) is 3.06 m, calculated according to the formula (L.sub.1+L.sub.4)×i.sub.0−L.sub.1×i.sub.1=(L.sub.1+L.sub.2+L.sub.3)×i.sub.0−L.sub.1×i.sub.1=(18.0+4.0+0.5)×0.20−18.0×0.08. Because h.sub.11 is greater than 0.3 m, h.sub.11 does not satisfy the given conditions. The length L.sub.1 of the step section (2) is 16.0 m, which satisfies the formula of L.sub.1/4≦L.sub.4≦L.sub.1/2, and the suspension height h.sub.11 of the lower indented sill (4) is 2.82 m, obtained using the formula (L.sub.1+L.sub.4)×i.sub.0−L.sub.1×i.sub.1=(L.sub.1+L.sub.2+L.sub.3)×i.sub.0−L.sub.1×i.sub.1=(16.0+4.0+0.5)×0.20−16.0×0.08.

(21) Based on the density of the debris flow and the suspension height h.sub.11 of the lower indented sill (4), the thickness h.sub.13 of the cable net cage bottom protection (6) is 0.5 m, the cable diameter of the cable net cage bottom protection (6) and the cable net cage buffer layer (7) is 0.005 m, and the mesh size of the cable net is 0.1 m*0.1 m. In addition, the extra-buried depth h.sub.14 of the lower indented sill (4) is 0.5 m.

(22) The height h.sub.1 of the lower indented sill (4) is 4.82 m (i.e., h.sub.11+h.sub.12+h.sub.13+h.sub.14=2.82+1.0+0.5+0.5), and the height h.sub.2 of the upper indented sill (3) is 1.5 m (i.e., h.sub.12+h.sub.13=1.0+0.5).

(23) Summarizing, the key parameters of the debris flow drainage channel with a step pool structure are as follows: the average gully bed longitudinal slope i.sub.0 of the channel bottom is 0.20, the width B of the drainage channel bottom is 10.0 m, and the depth H of the drainage channel is 5.0 m. For the step section (2), the slope i.sub.1 of the step section (2) is 0.08, the length L.sub.1 of the step section (2) is 16.0 m, h.sub.2 of the upper indented sill (3) is 1.5 m, and the height h.sub.1 of the lower indented sill (4) is 4.82 m. The fully lined baseplate (5) is a cement-laid stone masonry structure with a thickness of 0.5 m. For the pool section, the laying length L.sub.2 of the block stones (8) is 4.0 m, the laying thickness h.sub.12 of the block stones (8) is 1.0 m, and the particle size of the block stones (8) is 0.2 m. The thickness L.sub.3 of the cable net cage buffer layer (7) is 0.5 m, the height of the cable net cage buffer layer (7) is 1.0 m, the thickness h.sub.13 of the cable net cage bottom protection (6) is 0.5 m, the length of the cable net cage bottom protection (6) is 4.5 m, the cable diameter of the cable net cage bottom protection (6) and the cable net cage buffer layer (7) is 0.005 m, the mesh size of the cable net is 0.1 m*0.1 m, and the suspension height h.sub.11 of the lower indented sill (4) is 2.82 m.