1. Drainage guide groove
The discharge guide groove can be divided into sharp bottom groove, flat bottom groove and V-shaped fixed bed groove. The sharp bottom has V-shaped and circular grooves, the flat bottom has trapezoidal and rectangular grooves, and the V-shaped fixed bed groove is a stepped threshold.
(1) Sharp bottom groove (V bottom shape, round bottom shape, bow bottom shape)
Set in the debris flow accumulation area, it has the functions of guiding the flow direction, improving the flow velocity, discharging solid substances and preventing debris flow deposition. The cross-sectional form of the sharp bottom groove is shown in Figure 3- 17.
Fig. 3- 17 schematic diagram of cross-section form of sharp bottom groove
(2) Flat-bottomed groove (trapezoid, rectangle)
It is often used in the spillway of clear water flow, but it is not ideal for the discharge of debris flow solid materials. The application in the debris flow ditch of Chengdu-Kunming line proves that it is not advisable to discharge debris flow with flat-bottomed trough. The cross-sectional form of the flat-bottomed groove is shown in Figure 3- 18.
(3)V-shaped fixed bed trough (V-shaped stepped threshold)
Fig. 3- 18 schematic diagram of cross-sectional form of flat-bottomed trough
It is used in the debris flow forming area to discharge the flood in the upstream clear water area, and avoid cutting ditches, scouring the bank of ditches or scouring the foot of slopes when passing through the debris flow forming area, so as to fix the gully bed and stabilize the mountain, thus controlling the scale and development of debris flow and reducing the harm of debris flow. Fig. 3- 19 is a schematic diagram of a V-shaped fixed bed storage tank.
Fig. 3-3- 19V fixed bed storage tank schematic diagram
2. Diversion dike
Diversion dikes are usually divided into beam dikes and downstream dikes. Water surface protection has the functions of changing the flow direction and velocity, preventing overflow, and protecting the bank and foot of slope.
(1) beam dike
It is used to compress the river, limit the width of the flow path, yield to the flow direction, drain into the canal, prevent turbulence, deflection, bypass and lateral erosion, and has the function of enhancing drainage capacity. Figure 3-20 is a schematic diagram of the beam dike.
Figure 3-20 Schematic Diagram of Bundle Flow Embankment
(2) Downstream dike
It is often built parallel to the direction of water flow, used for drainage and diversion, returning to the trough downstream, controlling river regime, preventing overflow from changing direction and protecting bank erosion. Figure 3-2 1 is the schematic diagram of the downstream breakwater.
Figure 3-2 1 Schematic diagram of downstream dike
3. Pinch the brake
Diversion dam can be divided into downstream dam and bucket dam. There is a mandatory effect, and the dam body is shorter and stronger.
(1) downstream dam
It is used to change the ditch and plug the mouth, and has the functions of intercepting, draining, flowing downstream in the river bend, forced downstream and discharging into the ditch (bridge). Figure 3-22 is a schematic diagram of the downstream dam.
Figure 3-22 Schematic Diagram of Downstream Dam
(2) flap dam
Forcibly change the flow direction, ease the flow potential, limit the width of the flow path, prevent turbulence, deviation, bypass and lateral erosion or accumulation, and protect key construction projects. Figure 3-23 is a schematic diagram of the dam.
Fig. 3-23 Schematic diagram of flap dam
The best drainage engineering system, which is effectively composed of troughs, dikes and dams, can fully discharge debris flow, make it move along the specified direction and flow path, prevent overflow, diversion and siltation of debris flow, and reduce debris flow disasters.