Can the teacher give a model for the construction scheme of slope shotcrete (hanging net shotcrete slope protection) thank you

Taking expressway Project of the Third Opening as an example, this paper introduces the mechanism, method, function and construction technology of sprayed concrete vegetation protection for rock cutting slope.

Keywords: shotcrete construction technology of rock slope

1 project overview

Sansui to Kaili expressway is a section of the national trunk line from Shanghai to Ruili. It is a horizontal section of the national trunk network "five verticals and seven verticals" planned by the state, an important section of the highway network "two verticals, two verticals and four links" planned by Guizhou Province, and an environmental protection pilot highway planned by the Ministry of Communications. This section is located in Qiandongnan Prefecture, Guizhou Province, with subtropical mild and humid monsoon climate, abundant rainfall, rolling mountains and dense vegetation in the area where the highway passes. After cutting excavation, some slopes are rock slopes. Aiming at this kind of slope, the new concept of green protection is introduced in the design, and green concrete is used to treat the slope.

2. Mechanism of shotcrete protecting rock slope

Commonly used slope protection can be roughly divided into engineering and vegetation methods. Engineering protection methods include masonry slope protection, skeleton, retaining wall fence, anchor cable, shotcrete and other traditional engineering protection methods; Plant protection method is to plant trees and grass on the basis of stabilizing slope as a measure to prevent rain erosion and control topsoil loss. With the emphasis on environmental protection, it is the general trend to combine engineering protection with plant protection as much as possible.

Rock slopes are generally stable, and the stability of slopes reinforced by engineering is more secure. However, exposed rocks not only affect the landscape and destroy the environment, but also cause serious weathering and even slope instability for a long time. Shotcrete slope protection technology is developed in view of the situation that rock slopes can not be afforested in the past. Its principle is to use high-order aggregates to form a dense structure of exotic soil, in which plant fibers play the role of opening nets similar to plant roots, creating a growth foundation that is resistant to rainfall erosion, firm and breathable, and similar to natural topsoil. Shotcrete is mainly used for rock slopes and hard sprayed land, which makes it possible to restore natural ecology, protect the environment and beautify the landscape. Shotcrete will play an ideal protective purpose after the engineering measures of anchor rod hanging net are adopted for rock slope, and it is an ideal protective method for rock slope.

3 rock cutting slope protection design

Bolts are made of threaded steel bars, with a diameter of 12mm and a spacing of 1* 1m, arranged in a square, and the anchoring depth of bolts is generally 2m. Enclosed anchors are added at the edges of barbed wire on both sides, with a distance of 0.5m and a depth of 0.5m. The anchor rods are anchored by mortar, and the wire mesh is galvanized iron wire. The specification of the barbed wire is 14mm, and the mesh is 5cm*5cm. The barbed wire is closely connected with the anchor rod at the end. At a distance of 2.5cm from the slope, the barbed wire is generally in a taut and straight state. The raw materials (plant mixture) of shotcrete are sprayed on the slope by shotcrete machine to form shotcrete. The maintenance work shall start on the day after spraying and last for six months. During the maintenance period, we should always pay attention to plant growth and weather conditions, and make necessary water wetting and nutritional supplement. In principle, apply fertilizer once every two months and use compound fertilizer. After half a year, the vegetation coverage rate should reach more than 90%.

4. The main components and functions of raw materials for shotcrete base materials

4. 1 Planting soil and organic fertilizer

It is the soil and nutrient for plant growth and the basic substance for plant growth. It is natural, sterile, green, ventilated, drainage and water-retaining, and contains high organic matter, corrosive acid and nutrients, so it can be used as a long-acting slow-release fertilizer.

4.2 Wood fiber

It is the connecting material between the greening substrate and the barbed wire on the slope in the early stage. After the roots of herbs were inserted into the cracks in the rocks, the connection failed. When paper pulp can be used as a substitute for wood fiber, we should pay attention to the following shortcomings: the pulp may contain substances harmful to grass seed germination, such as too high PH value and too fine fiber, which may easily lead to poor interweaving, hardening, poor water absorption and water retention, and "crusting" after drying. In addition, the high water content of pulp brings many troubles to supply, packaging, transportation and construction.

4.3 sawdust

It can retain water in the matrix, reduce the unit weight of the matrix, increase the internal friction angle of the matrix, and thus reduce the sliding force of the matrix on the slope. It works together with wood fiber to stabilize the greening matrix on rock slope, and it is a good fertilizer after corrosion with wood fiber.

4.4 Coarse river sand

It is a loosening agent in greening matrix, which can effectively prevent greening matrix from hardening, make sprayed concrete firm and breathable, and is beneficial to plant growth.

4.5 Polymer Additives