At present, the construction of mountain expressways in China is developing rapidly. In the construction of high-grade highway, a large number of deep excavation and high fill embankment slopes have appeared, and their protection problems are very prominent. In order to meet the dual objectives of safety, reliability and economic rationality, it is very important to deeply analyze the characteristics of high slope diseases and carefully choose its treatment project.
Highway slopes are widely distributed along the highway, which destroys the natural environment. If we can pay attention to protecting and creating the environment while protecting, and adopt appropriate greening protection methods, the highway will have the characteristics of safety, comfort, beauty and harmony with the environment, and will also produce considerable economic, social and ecological benefits. In order to protect highway slopes, the following problems must be considered:
① Slope stability: protect the surface of subgrade slope from rain erosion, slow down the influence of temperature difference and temperature change, and prevent and delay the evolution process of weathering, crushing and erosion of soft rock and soil surface, thus protecting the overall stability of subgrade.
(2) Environmental protection: minimize the interference of the project to the environment and seek the harmony between artificial structures and the natural environment.
③ Comprehensive effect: comprehensively prevent light, glare and smoke, induce the driver's sight and improve the landscape, and give full play to the comprehensive benefits of the protection project.
1, engineering protection
1. 1 Plastering and knocking
1. 1. 1 applicable conditions:
(1) For all kinds of easily weathered soft rocks (such as argillaceous sandstone, shale, phyllite, argillaceous slate, etc. ) slope, when the rock weathering is not very serious;
(2) The protected slope itself must be stable, but its slope shape, steepness and smoothness are not limited;
③ The protected slope must be a dry rock slope without groundwater.
1. 1.2 structural requirements:
(1) The plastering thickness is generally 5 ~ 7 cm, and the plastering thickness is 10 ~ 15 cm, which is generally of equal thickness.
(2) The joints around plastering and stress surface works and unprotected slopes shall be strictly closed. If the intercepting ditch is located at the top of the slope, the bottom and side of the ditch should also be plastered or reinforced for protection.
(3) When plastering or tamping a large area, an expansion joint shall be set every 5 ~ 10m.
1.2 grouting and joints
Grouting is suitable for rock cutting slopes with hard rocks, severe weathering, well-developed rock joints and small crack width.
Joints are suitable for rock cutting slopes with hard rocks, hard weathering, undeveloped joints and large and deep joints.
1.3 Cement-soil slope protection
1.3. 1 Applicable conditions:
① Suitable for slope filling of silt, silt, silty clay and clay.
(2) Subgrade fill slope that is easy to be flooded.
③ It can be used in saline soil area.
Structural requirements of 1.3.2: the thickness of cement-soil slope protection is generally 10 ~ 20 cm. The cement content is generally 8% ~ 15%, and the specific content is determined according to the field test during construction.
1.4 facing wall
1.4. 1 Applicable conditions:
① It is mostly used in strongly weathered soft rock and broken rock sections such as easily weathered mica rock, chlorite schist and phyllite to prevent further weathering;
(2) The slope itself must be stable;
(3) There are solid decorative walls, perforated window decorative walls, arched decorative walls and ribbed decorative walls. The solid facing wall is suitable for general soil and gravel slopes; Empty window retaining wall is used for slope less than 1: 0.75, and hole window can be used for punching face (when the slope is dry) or dry masonry flaky; When the lower rock layer of the slope is relatively complete, the arch retaining wall is used to protect the upper slope, or when passing through individual weak areas, when the rock layer of the slope is relatively complete and the slope is steep, the rib retaining wall is used.
1.4.2 structural requirements
(1) solid facing wall
The thickness of (1) depends on the wall height, generally 0.4~0.6m, and the bottom width is generally equal to the top width plus h/10 ~ h/20; Generally, the height of single-stage retaining wall shall not exceed 15m, and the total height of multi-stage retaining wall shall not exceed 30m.
(2) Set a 2cm expansion joint every 10m along the wall length, and reinforce the joint with asphalt hemp reinforcement. After the drainage hole, gravel and sand are used as the filter layer to eliminate the drainage behind the wall.
(3) Before the retaining wall is built, all slopes should be cleared of weathered layer to fresh rock layer. For slopes containing rapidly weathered rocks (such as mica and chlorite schist), retaining walls should be built immediately after fresh rock surfaces are removed.
(4) The top shall be rammed with original soil to avoid soil erosion.
(2) Window-hole facing wall
The openings of perforated window facing walls are generally semicircular arches, with a height of 2.5~3.5m, a width of 2 ~ 3m and a radius of1~1.5m. The foundation, thickness, expansion joints and so on are the same as those of solid facing walls, and the openings are made of dry masonry, grass planting or surface drilling according to specific conditions.
(3) Arch retaining wall
When the span of the arch ring is small (2 ~ 3m), 10# cement mortar flaky can be used for the arch ring, and the height of the arch ring depends on the height of the complete rock layer under the slope. When the span of arch ring is large, concrete arch ring can be used.
1.5 shotcrete or shotcrete protection
1.5. 1 Applicable conditions:
① It is suitable for rocky slopes with poor lithology, low strength, easy weathering or hard rock weathering, joint development and surface weathering and peeling;
(2) When the rock slope is broken in a large area due to weathering, peeling, joint cutting and other reasons, as well as local small-scale collapse and rockfall, local reinforcement can be carried out first, and then large-scale shotcrete can be carried out.
(3) High cutting slope with weathered upper rock layer and hard and complete lower rock layer;
(4) Can't bear the mountain pressure, and the slope must be stable.
1.5.2 structural requirements
(1) The thickness of sprayed concrete should not be less than 1.5 ~ 2 cm, and the thickness of sprayed concrete should be 3 ~ 5 cm.
(2) In order to prevent slope water from scouring, a small intercepting ditch is set along the outer side of the upper edge of sprayed concrete slope.
(3) The gouges on both sides of the mud are embedded in the rock stratum.
1.6 spray anchor protection
1.6. 1 Applicable conditions:
Where the rock slope is easy to be protected by shotcrete, when the rock layer is severely weathered and broken and joints are developed, if the broken rock layer is thick, it will lead to falling rocks or small collapses, thus affecting the stability of the whole slope. It has high strength and good crack resistance, and can reinforce the broken rock stratum at a certain depth on the slope and bear the lateral pressure generated by a small amount of broken bodies. Disadvantages: high cost, high energy consumption, difficult construction, long construction period, difficult slope greening and unsightly.
2. Plant protection
2. 1 Planting grass
2. 1. 1 applicable conditions
For embankments or cutting slopes with stable slopes and slight slope erosion, it is generally required that the slope gradient should not be greater than 1: 1, and the slope water flow velocity should not exceed 0.6m/s, which is not suitable for long-term submerged slopes.
2. 1.2 planting pattern
According to different construction methods, there are the following ways:
(1) Seed sowing method: suitable for soft soil, sandy soil with thickness less than 25mm and cohesive soil with thickness less than 23mm, with slope less than 1: 1.
(2) Spray seeding method: it is suitable for gravelly soil with sand between gravels, sandy soil with a thickness less than 25mm, cohesive soil with a thickness less than 23mm, cohesive soil slope with a thickness greater than 25mm, or hard soil with a thickness greater than 25mm, and can be used in conjunction with carpet laying projects in areas with frequent rainstorms.
(3) Exotic soil spray seeding method [5]: Exotic soil spray seeding technology is a new technology to improve the slope planting environment, promote plant growth, realize three-dimensional greening, and restore the natural vegetation on the slope that cannot be afforested or has poor greening effect under ordinary conditions. The method of spray seeding with foreign soil has wide adaptability, and is suitable for both soil slopes and rock slopes.
(4) Acupoint ditching method
Methods: The point-and-click method is to dig holes with a diameter of 5 ~ 8 cm and a depth of 65,438+00 ~ 65,438+05 cm on the slope, with about 8 ~ 65,438+02 holes per square meter to prevent solid fertilizer from entering, and to bury the holes with soil and sand before sowing. Trenching method is to dig a trench with a depth of 10 ~ 15 cm on the slope with a horizontal spacing of about 50cm, and then put in fertilizer and sow.
Suitable for: the site conditions of green space on both sides of the highway are poor, such as hard soil or granite weathered sandy soil excavation slope.
2.2 Laying turf
2.2. 1 applicable conditions
Various soil slopes, especially steep slopes with serious erosion (up to 60? ), when the runoff velocity reaches 0.6m/s.
2.2.2 Turf paving method
Paving, horizontal lap, vertical or oblique lap and slope half broken, and paving square or arch frame with flaky, paving turf in square, etc.
2.3 planting trees
It is suitable for all kinds of soil slopes and strongly weathered rock slopes, and the slope is not steeper than 1: 1.5. Planting plants on subgrade slopes and floodplains has achieved good results in strengthening subgrade and protecting river banks. It can reduce the flow rate of water, and planting on the river beach can promote sediment deposition and prevent water from directly scouring the bank. Planting trees is best combined with planting grass. It is forbidden to plant trees on the slopes of high-grade highways. Disadvantages: the applicable slope range is small. In some areas with poor soil environment, plants can't get the nutrients needed for growth, and the survival rate is low, which affects the stability and beauty of slopes.
-3. Flexible support system
3. 1 system introduction
This is an international advanced slope treatment technology. This technology is a new patented invention technology introduced from Canada. It is a new technology to form a solid wall slope protection structure by using an ecological bag which is impermeable to water, soil, acid and alkali, non-toxic, non-degradable, anti-ultraviolet, plant-friendly and green, and through special reinforcement methods such as connecting buttons, adhesives and anchor rods, to construct a new soft slope structure with good plant growth conditions. The theoretical basis of reinforced retaining wall structure of slope flexible support technology is based on soil mechanics Mohr? The basic principle of reinforced soil theory developed from Coulomb theory. The overall stress of the slope formed by the regular triangle+connecting buckle+vegetation root strengthening locking structure is scientific and stable, which has the functions of absorbing energy and buffering external impact, and its seismic performance is incomparable to that of traditional slopes. 3.2 The system has good soil consolidation. Ecological bags, steel bar anchors, geogrids, connecting buckles, etc. are connected with the slope to form a stable mechanical structure, forming a new type of soft slope which is water-permeable and soil-impermeable and friendly to plants. Plant roots grow freely through this new soft slope and enter the geotechnical basement to form countless anchors, thus creating a stable, permanent and vital ecological slope.
3.2. 1 system has strong stability. The triangular internal friction locking structure composed of ecological bag and connecting buckle is stressed as a whole, which has scientific stability, can absorb energy and buffer external impact. With the development of plant roots, the slope reinforcement effect is further strengthened, and the seismic performance is incomparable to traditional slopes.
The structural plane is combined with the slope through the root system with developed vegetation, so that the artificial slope and the original natural slope will not be separated and collapsed. And with the passage of time, the increasingly vigorous vegetation roots make the slope structure more stable and firm, so it is a natural, living and breathing permanent ecological project.
On that basi of reinforcing the regular triangle loc structure, the invention increases the mutual adhesion between bags, so that the overall stress has better stability and the ecological retain wall is more stable.
3.2.2 The construction is simple, and everyone can participate in the construction under the guidance of construction guidance and technicians, without any technical experience in slope construction, thus solving the employment problem of a large number of surplus labor. General foundation engineering does not need special treatment, and the adaptability to uneven settlement is one of the characteristics of this system. At the same time, the structure will not produce temperature stress, and there is no need to set temperature expansion joints. Not affected by the weather, the construction is fast and convenient, without? Three links and one leveling? Material handling is very light.
3.2.3 The choice of plants can be diversified.
3.2.4 To solve the technical problems of traditional slopes, vegetation can be quickly constructed and quickly integrated with surrounding vegetation to promote the overall coordination and unity of the landscape. The flower fairy ecosystem can choose plants suitable for local climate characteristics, and organically combine grass, vines, shrubs and trees, so that plants are not easy to degrade and the later maintenance cost is greatly reduced. The landscape can be built at will as required, with good landscape effect and reduced greenhouse effect. It is beneficial to the rapid restoration of the ecosystem and the rapid restoration of the slope environment to the natural state.