Sand barrier and sand fixation

1 sand barrier setting method and key areas

1. 1 sand barrier is laid or erected with firewood, branches and leaves of active psammophytes or other materials on the ground of wind-eroded sand dunes, so as to increase the roughness of the ground, weaken the near-surface wind speed, fix the sand grains on the ground, and slow down and prevent the sand dunes from flowing.

1.2 In key areas where sand barriers are used, for mobile sand dunes and semi-mobile sand dunes, sand barriers should be used to fix sand to prevent sand dunes from flowing, and then windbreak and sand-fixing forest belts and farmland shelterbelts should be built.

2 Classification of sand barriers

2. 1 According to the ground distribution shape of sand barriers, it can be divided into:

2. 1. 1 banded sand barrier. Sand barriers are distributed in strips on the ground, and the strip direction is perpendicular to the main wind direction.

2. 1.2 grid (or mesh) sand barrier. Sand barriers are distributed in a grid (or mesh) on the ground, and are mainly used in places where the wind direction is unstable and there is strong crosswind except the main wind direction.

2.2 According to the different sand barrier materials, it can be divided into:

2.2. 1 firewood sand barrier. Most of them are made of firewood or crop straw, which is the main material for laying sand barriers.

2.2.2 Clay sand barrier. In a few places where the sand layer is shallow or there is alkali beach near the sand dunes, clay is used to press the sand and pile it into soil ridges to make sand barriers.

2.2.3 Use pebbles or other materials (such as branches and leaves of active psammophytes) to make sand barriers.

2.3 According to the angle between firewood and the ground, sand barriers are laid.

2.3. 1 ceramic tile sand barrier. Spread firewood on the ground as a sand barrier, press branches to sand or fix them with small stakes.

2.3.2 Vertical sand barrier. Put firewood up as a sand barrier, some buried in the sand and some exposed on the ground.

3 Design and construction of sand barrier

3. 1 Design and construction of ceramic tile sand barrier

3. 1. 1 ribbon tile type

The belt runs perpendicular to the main wind direction. The bandwidth is 0.6 ~ 1.0m, the belt spacing is 4 ~ 5m, and the covering material is laid flat on the sand dunes with a thickness of 3 ~ 5cm. Covering materials include firewood, straw, branches or clay, pebbles, etc. When the cover is firewood and branches, the branches should be pressed horizontally and fixed with small stakes, or wet sand should be spread on the center line of the grass belt with the firewood tip facing the wind.

3. 1.2 completely tiled

Suitable for small and isolated sand dunes, both sides of roads buried or threatened by quicksand, farmland and around villages and towns. Spread mulch tightly on the sand dunes. Other requirements are the same as 2.3. 1. 1.

3.2 Design and Construction of Vertical Sand Barrier

3.2. 1 vertical sand barrier classification

3.2. 1. 1 The high vertical sand barrier is made of high-quality and tough firewood, with a length of 0.7 ~ 1.3m, 0.5~ 1.0m above the ground, 0.2~0.3m underground and 0.5 ~1.

3.2. 1.2 low vertical sand barrier, using soft wood, exposed to the ground for 0.2~0.3m, buried for 0.15 ~ 0.20m. ..

3.2.2 Plane configuration of vertical sand barrier

3.2.2. 1 perpendicular to the main wind direction of the area dominated by one-way sand blowing, arranged in a strip shape.

When the 3.2.2.2 is set on a crescent-shaped dune, there is a section on the top of the mountain, and a plurality of arc-shaped sand barriers (corresponding to the crescent radian) are set from top to bottom on the windward slope.

3.2.3 Distance between vertical sand barriers

3.2.3. 1.40 Dry and gentle sandy land, with the spacing between high vertical sand barriers being 10 ~ 15 times of the height of sand barriers, and the spacing between low vertical sand barriers being 2 ~ 4m.

The sand barrier set on the windward slope of 3.2.3.2 dunes should make the top of the next sand barrier 5 ~ 8 cm higher than the bottom of the previous one.

In 3.2.3.3, where the sand dune slope is large, the sand barrier spacing is calculated according to the formula (6- 1):

Series of standard textbooks for comprehensive management of soil and water conservation

Where: d-sand barrier spacing, m;

H—— height of sand barrier, m;

θ-the slope and degree of sand dunes.

3.2.4 Construction of vertical firewood sand barriers

3.2.4. 1 high vertical sand barrier construction. At the position of the designed sand barrier, the depth of the artificial trench is 0.2~0.3m, the firewood is vertically and uniformly buried, righted and compacted, the sand is filled with 0. 1m, and the firewood is exposed to the ground for 0.5 ~1.0m.. ..

Construction of low vertical sand barrier in 3.2.4.2. Cut firewood according to the designed length and put it on the line evenly along the designed sand barrier belt line. The direction of the grass is orthogonal to the strip line. Step on the firewood with your feet, and the firewood will enter the sandy land by 0. 1 ~ 0. 15m, with both ends upturned and the height of 0.2 ~ 0.3m Stand upright with your hands, and cultivate the sandy land at the bottom.

3.2.5 Design and construction of clay sand barrier

Clay sand barrier is a low vertical sand barrier. Generally, it is arranged at about 2/3 of the windward side of sand dunes from bottom to top. Embankment is clay alkaline earth, with a height of 0.20 ~ 0.25m, a bottom width of 0.6 ~ 0.8m and an arc-shaped top. The spacing between soil ridges is 2 ~ 4m.

Second, understanding and implementation

This part mainly introduces the classification, design and construction. Sand barrier, also known as wind barrier, is the main measure of sand fixation in engineering, which is used to slow down the surface wind speed and fix the moving hills and semi-moving sand dunes. Strip sand barriers are mostly used in areas with single wind direction, while grid sand barriers are mostly used in areas with multiple wind directions. In order to prevent wind erosion, semi-hidden sand barriers should be selected; When intercepting the wind-blown sand flow, the high vertical sand barrier with ventilation structure should be selected; High vertical sand barriers with compact structure should be selected to change the terrain. Sand barrier design is mainly to design the direction, spacing, height, density, buried depth and material of sand barrier. The direction of sand barrier should be perpendicular to the main wind direction. The spacing depends on the slope of the ground, the height of the sand barrier and the wind. The interval between high sand barrier, gentle slope and weak wind can be larger, and vice versa. The selection of materials for making sand barriers mainly considers the following aspects: easy access, low price, good effect, long storage time and little side effects, such as wheat straw, straw, branches, reeds, gravel and clay. When laying straw and forage sand barriers, windless weather should be chosen, starting from the windward side, and the density should be higher in places with strong wind or strong sand mobility.

Due to the relatively mature technology of sand barrier fixation, the new standard has not been greatly modified compared with the original standard, but some redundant words have been deleted. For example, in the classification of vertical sand barriers in the original standard 4.3.2. 1 "According to the vertical height of firewood, there are two types of vertical sand barriers with different design and construction requirements", the words "spacing requirements" in 4.3.2.3.2 and the words "design and construction requirements" in 4.3.2.5 were deleted.

Third, examples.

Sand barrier sand fixation technology has been widely used in the vast sand-blown areas in northern China. After years of practical experience in sand barrier and sand fixation, combined with the contents of this standard, some practices and typical examples of sand prevention and control are summarized, which are worth learning and learning.

Example 1: Study on Wind-proof and Sand-fixing Benefits of Salix psammophila Living Barrier in Hunshandake Sandy Land

1. Overview of natural areas

Hunshandake Sandy Land is located in the farming-pastoral ecotone in the middle of Inner Mongolia Autonomous Region, with the geographical position of 4156' ~ 44 24' north latitude and 0/12 22' ~17 57' east longitude. The natural area belongs to temperate semi-arid area and At the end of 1950s, Hunshandake Sandy Land was the place with the highest dune fixation, the richest animal and plant species and the best ecological landscape among all desert sandy lands in China. However, due to the frequent occurrence of climate drought, population increase and uncontrolled development and utilization, the sand landscape in this area has been seriously degraded or even destroyed, resulting in frequent sandstorm activities, which has become one of the main sand sources of sandstorms in Beijing, Tianjin and even North China. With the increasing spread of desertification and the frequent occurrence of sandstorms, the governance, ecological construction and environmental protection of Hunshandake sandy land have been widely concerned by the whole society.

Willow is widely distributed in Hunshandake sandy land. Because it has the characteristics of drought resistance, wind erosion resistance and sand burial resistance, the survival rate of cutting is high, and it is a very valuable building material for living sand barriers. Especially in Hunshandake sandy land, the precipitation is about 350 mm, which has unique advantages for the establishment of biological sand barriers. Therefore, since 2000, Hunshandake Sandy Land began to use Salix psammophila to control quicksand.

2. Design and construction of Salix psammophila living sand barrier

The cuttings used in the Salix psammophila living sand barrier are 3-4 year-old robust branches, the length of cuttings is 50cm, the depth of cuttings is about 45-50 cm, the cuttings are exposed to the ground for about 5cm or the cuttings are flush with the ground, and the number of cuttings per meter is not less than 13 to ensure high survival rate. The sand barrier is set perpendicular to the main wind direction. Ribbon sand barriers are generally used in areas with single main wind direction, while grid sand barriers are mostly used in areas with changeable wind direction or key control areas. Their specifications include 4m×4m grid sand barrier, 6m×6m grid sand barrier, 4m interval belt sand barrier and 6m interval belt sand barrier. It is determined that the effect of 4m×4m grid sand barrier in Hunshandake sandy land is the most obvious.

Example 2: Application of Grass Checked Sand Barrier in Sand Prevention of Qidun Beach

Grass grid sand barrier is also a very effective and applicable sand fixation method. It uses various materials (straw, straw, reed, etc.). ) form obstacles that interfere with the operation of sandstorm flow on the surface. By changing the nature of the underlying surface, increasing the roughness of the ground and transforming the movement conditions of sandstorms, it is widely used to fix quicksand and prevent sand dunes from moving forward.

1. Overview of natural areas

Qiduntan Irrigation District of Shule River Project is located in the west of Hexi Corridor, in the middle and lower reaches of Shule River, with a total area of 35,600 mu. In the development of irrigation area, only a small amount of vegetation is destroyed, which leads to the aggravation of sandstorm. The total area of semi-fixed or mobile sand dunes is 6667 mu, and the sand dunes vary in size, with a height of 1 ~ 3m. The movement of sand dunes blocked supporting channels, covered farmland, blocked roads, and residential areas and public facilities were attacked by sandstorms. A large number of sandstorms accumulated in the courtyard, and the courtyard walls were overwhelmed, which seriously affected the normal production, life and development of immigrants in irrigation areas. Because Qidun Beach is surrounded by oasis, there is no external sand source, and the local wind and sand source is mainly contiguous sand dunes or star-shaped sand dunes in the project area. Therefore, the main measure for sand prevention and control is to use grass barriers to fix sand.

2. Design and construction of grass grid sand barrier

The specification of grass fence sand barrier is the size of grass belt spacing, which depends on the wind power in the area. A belt-shaped grass grid sand barrier can be set in a single wind direction area perpendicular to the wind direction; In areas where the wind direction changes with the seasons, a grid-like grass grid sand barrier should be made.

Grass checkered sand barriers have different specifications. From the perspective of sand fixation effect, the smaller the specification, the better, and the larger the specification, the cheaper it is. The shape of the grass square is square. Four different specifications,1.0m× 1.5m× 1.5m×1.5m, 2.0m×2.0m, 5.0m×5.0m, have been adopted to control wind-blown sand in Qiduntan irrigation area of Shule River. The results show that the sand fixation effect of the 5.0m× 5.0m× 2.0m grass barrier is not obvious, while the sand fixation effect of 1.5m× 1.5m grass barrier is not as good as that of 1.0m× 1.0m grass barrier. Practice has proved that the grass net of 1.0m× 1.0m is the most reasonable on the sand surface with little topographic fluctuation, and the specifications of the grass net can be flexibly enlarged on the flat sand surface with less wind.