(1) Rock slope protection. This structure is widely used in revetment engineering, and has the advantages of local materials, simple and flexible construction, adaptation to riverbed deformation, phased implementation and gradual reinforcement. Stone can be used for upper slope protection and lower toe protection of this project. The slope protection projects in the middle and lower reaches of the Yangtze River mostly use mortar masonry and dry masonry, and scattered riprap is used to protect the feet, with a slope of 1:2.5~l:3.0. This section is composed of toe groove, slope surface and roof. The thickness of slope protection is 0.3 ~ 0.4 m, and the cushion plays a filtering role. The toe protection riprap thickness is 0.6 ~ 1.0m, the stable slope is not steeper than 1:l.5, and some parts are gently reinforced to above 1:2. The riprap range generally reaches the bed surface or depth of l:3~ 1:4. The average nearshore velocity is 3 m/s, and the stone particle size is generally 0.2~0.4 m, and the stone weight is 20~50 kg.
Since the 1970s, geosynthetics have been widely used to replace sand and gravel filter materials in Europe, the United States and Japan, and have also been popularized and applied in China.
(2) Liushi revetment. Tuogong is a river construction with a long history in China, which was widely used in the Yellow River and Yongding River. Liushi pillow and Liushi arm box are commonly used masonry structures. Its main advantages are flexibility, stone saving and good protective effect. The main disadvantage is that it is not durable, especially the willow branches exposed to the water are easy to rot. Generally, boats or floating pillows are used as the working platform on the water, and cables are piled on the shore, and willow stones are laid on the cables, and ropes are tied with short piles, so that the willow stones are repeatedly stacked until they sink to the bottom of the river, and then all the ropes are tied back to the top piles on the shore, and then the thickness of throwing soil is 1.0~ 1.5 m, so that the roots near the river can be reinforced by throwing pillows. When there are few stones, silt blocks can be used instead of stones. When willows are scarce, firewood and reeds can be used instead.
Liushi pillow is a cylinder wrapped with willow branches, with a diameter of 0.7~ 1. Om, the length is 3~ 10 m as required. In some places, willow stone pillows are often used in revetment and toe protection projects in the lower reaches of the Yellow River and the middle and lower reaches of the Yangtze River.
(3) Gabion revetment. Widely adopted by various countries. Made of lead wire, bamboo strips, Vitex negundo, etc. Into a variety of grid-like cage-like objects, filled with stones, gravel or pebbles, the grid size should not leak stones. These components are discharged tightly from the bottom of the river in turn to protect the feet below the lowest dry water level. In 250 BC, when China built the famous Dujiangyan, it used gabions and bridges to divert water and intercept it. Gabion cages have been used in Europe for more than 100 years.
(4) Underwater revetment. Sinking row is generally used for foot protection or bottom protection, and it is crushed by riprap on the shore slope. Underwater revetment has the advantages of strong integrity, good toughness, adaptability to riverbed deformation and erosion resistance, but the cost is high and the construction technology is complicated.
(5) Concrete block revetment. Square or hexagonal precast concrete blocks with a thickness of 0. 1~0.3 m are mainly used to protect dikes, dams and river bank slopes from wind and waves. The revetment of sea and lake sometimes adopts concrete special-shaped blocks to protect the slope and feet.
(6) Geotextile revetment. Use geotextile, such as weaving into mould bags, pouring cement mortar or concrete to form mould bags for slope protection. It is also useful to fill sand and pebbles with geotextile long pipe bags for foot protection projects. In recent years, geotextiles, geogrids and geotextiles have been used as reinforcement materials to strengthen groins with soil cores and soft soil foundations, so as to improve the shear and tensile strength and integrity of soil.
(7) Permeable pile dam. A commonly used permeable building. There are generally wooden stakes and reinforced concrete pile dams. In 1950s, some stake dams were built in the lower reaches of the Yellow River where shallow water flows slowly. The dam length is about 40~80 m, and the dam spacing is 80~ 160 m. Each dam has 2~4 rows of piles, and the pile spacing is1m.. The stake driven into the river bottom is 2/3 of the length of the stake, and wicker fence is used between the stakes, which has a good effect of slow flow and siltation. Before the 1960s, pile dams were widely used in the lower reaches of the Mississippi River in the United States, consisting of two or more rows (at most seven rows) of piles. There are 3 piles in each group, with a spacing of 6. 1 m and a spacing of 1.52 m in each row. Longitudinal and transverse beams are arranged between two adjacent rows, and the dam crest is 4.6 m higher than the minimum water level. Pile foundation is protected by sinking wood or filling stone. The spacing of the stake dam is 65438+ 0~2 times of the upstream dam length. Pile dams have been developed to be built with reinforced concrete piles, driven by water drilling or vibrating pile drivers or cast-in-place concrete piles.
(8) Check the dam. Dujiangyan project of Minjiang River used Mujuecha dam to intercept and divert water for irrigation. The bridge is suitable for building groins and dams on sandy pebble riverbed.
(9) Biological revetment. Planting trees and grass can slow down the water flow, prevent erosion, and stabilize the beach and protect the embankment in the river section with wide and slow water flow. Tree planting can be arranged continuously or in strips, and tree species and grass species can be selected according to local conditions. Planting live willow dams in the lower reaches of the Yellow River and planting wild goose-winged forest and willow dams on the Yongding River is also a form of tree planting and beach protection project.
The above revetment forms can be used separately or in combination according to specific conditions.