Prevention and treatment of highway landslides and high slope diseases?

What is the specific content of highway landslide and high slope disease prevention? Zhong Da Consulting will answer your questions below.

The prevention and control of landslide and high slope diseases is essentially a process of maintaining or restoring the slope's own balance through engineering measures. In the highway construction in mountainous areas, after a large number of natural slopes are artificially transformed, some slopes will or may be unstable and deformed in whole or in part, which will endanger the safety of subgrade structure. At this time, it is necessary to deal with the slope. In the prevention and treatment of highway diseases and deep excavation of highway sections, according to the characteristics of diseases, we need to start from the following aspects:

First, the prevention and control principles of highway landslides and high slope diseases

In the deep excavation section of expressway, the prevention and control of diseases need to start from the following links.

1. 1 In the project initiation stage of highway projects, the reinforcement and protection standards of high slopes in deep excavation sections of highway construction projects in mountainous and hilly areas should be improved accordingly, and the long-term stability of highway slopes should be organically combined with the comprehensive management of ecological environment in mountainous areas;

1.2 In the highway design stage, strengthen geological survey, rationally select the route, try to avoid bad geological bodies, and prevent possible slope diseases in advance when it is impossible to avoid them;

1.3 In the highway construction stage, adopt reasonable construction methods and sequences to reinforce and protect the slope in time.

The selection of preventive measures is related to various factors and conditions, such as technical and economic effects, depth of survey work, construction methods and construction sequence. Generally, the following principles should be followed: ① Prevention first, avoiding as much as possible; (2) The right medicine and comprehensive treatment; Make up your mind early and deal with it in time; (4) Strive for radical cure and prevent future troubles; ⑤ Economical and reasonable, safe and reliable.

For large and complex slope disasters, route selection should be avoided as much as possible. If it is really unavoidable, reasonable comprehensive control measures should be taken. For each kind of slope disaster, the types of slope disasters and their engineering hydrogeological characteristics should be explained in detail, the main failure factors should be controlled, comprehensive consideration should be made, and various control measures should be used reasonably.

Second, the choice of design parameters

In disease control design, the selection of design parameters is very important, which is directly related to the safety and economic indicators of control engineering. Generally speaking, the sliding zone of landslide is generally attached to the weak interlayer, structural plane or the contact surface of soft and hard rock in the slope. The factors affecting the parameters of sliding belt are:

① Slope disease deformation stage. ② The current slope stability. ③ Survey season. ④ Test method. ⑤ The influence of treatment scheme on diseases. ⑥ Consider the change of design parameters under the most unfavorable conditions that may occur during the service life of the project.

Because the landslide is thin, it is difficult to sample, the shear value of remolded soil and undisturbed soil is quite different, or because the sliding zone soil contains coarse-grained substances, which will affect the test results during the shear test. In engineering practice, inversion algorithm is often used to determine the shear index, and the shear test results can be used as reference values. In the following cases, when calculating the sliding zone index, the back calculation results should be adjusted appropriately in combination with various influencing factors of landslide.

2. 1 Before the slope excavation or before the excavation is completed, the sliding zone is not completely formed. At this time, although the location of potential sliding zone can be found out through geological survey, the stability of landslide after slope excavation cannot be determined;

2.2 When landslide survey is carried out in dry season, its stability is high, and the reduction of stability coefficient in rainy season should be fully considered in back calculation;

2.3 Considering that human engineering activities have an impact on the stability of landslides.

Third, the governance engineering measures

With the development of large-scale expressway construction, a set of mature and complete treatment engineering technology has been formed for landslide and slope diseases, mainly based on new retaining structures, which are mainly considered from three aspects: ① using external force to offset the balanced sliding force, that is, increasing the sliding resistance of the sliding body; (2) increasing the shear strength of the sliding belt; ③ Reduce the sliding force. Generally, measures such as load reduction, anchoring, retaining soil, consolidation and drainage are adopted, that is, the combination of brush load reduction and anchoring support, supplemented by measures to intercept and drain surface water and groundwater. The selection should be considered comprehensively according to the specific situation in order to obtain the best economic and technical effect.

3. 1 Generally speaking, the reinforcement project of high and steep slopes is huge. In order to reduce the amount of reinforcement work and achieve reasonable economic results, measures such as stabilizing the foot of slope, reducing the height of sloping platform, widening the width of platform and slowing down the slope rate are considered. The unstable slope is controlled by the weak interlayer in the slope, and the dip angle is generally slow. It is difficult to completely remove the unstable body by brushing, but it can reduce the sliding force. Therefore, brush load reduction and reinforcement projects are often used together.

3.2 Prestressed Anchor Cable

Prestressed anchor cable is a kind of rod-shaped member that bears tension. It is anchored in deep stable stratum by drilling steel strand or high-strength steel wire, and prestressed on the surface of reinforced slope by stretching to stabilize the reinforced entity and limit its deformation.

3.3 Anti-slide pile

Excavate anti-slide piles on the landslide body to avoid large excavation from damaging its overall stability. The pile is embedded in the stable stratum below the sliding zone to resist the sliding force of the landslide. The prestressed anchor cable anti-slide pile changes the unreasonable cantilever stress state of ordinary anti-slide pile, which can greatly reduce the project cost and save materials such as steel and cement, and the economic benefit is very remarkable. After the general anti-slide pile is installed in the landslide, it will still deform to some extent. When there are important buildings on the landslide or at the front edge, no large deformation is allowed, which limits the application scope of anti-slide piles. Prestressed anchor cable anti-slide pile belongs to active stress structure, which applies prestress to the pile head through anchor cable and actively limits the deformation of landslide as needed.

3.4 anchor rod

Anchorage is generally divided into mechanical anchorage, adhesive anchorage and friction anchorage. However, cement mortar anchors with full-length anchorage are common in engineering. Anchor rod is mainly used to stabilize rock slope, which has the advantages of fast construction speed, flexible layout and low cost.

3.5 Grouting reinforcement

Before the slope excavation, the natural slope is pre-drilled with mud to reinforce the slope. However, due to the poor evaluation of grouting effect, it is generally only used as an auxiliary project.

3.6 Drainage measures

Drainage measures are divided into surface water and groundwater. The function of surface water is to intercept and drain the water on the hillside above the landslide area, prevent it from flowing into the landslide area, and discharge the precipitation and exposed part of groundwater in the landslide area as soon as possible through artificial ditches; Underground drainage measures can cut off the water supply of the sliding zone, reduce the groundwater level, reduce the pore water pressure on the sliding zone and improve its shear strength.

Fourth, the rational allocation of engineering measures

When choosing anti-slide pile or prestressed anchor cable, two factors are mainly considered: one is the position of anti-slide pile. Under normal circumstances, anti-slide piles should be arranged in rows in the anti-slide section of landslide front to make full use of the resistance of rock and soil in front of the piles, and other parts should only be considered under special circumstances or due to construction conditions. In the treatment of large-scale slope diseases, a single engineering measure is rarely adopted, and a combination of various engineering measures is often adopted. At present, the pile-anchor composite structure has been widely used in slope reinforcement, and practice has proved that this structure is economical and reasonable. Various combinations give full play to the advantages of the two treatment measures, and at the same time make up for their respective shortcomings.

Five, slope protection technology

5. 1 Slope waterproof and drainage measures

Waterproof and drainage design measures are one of the key factors to ensure slope stability. Rock is broken and cracks are developed on the slope, and groundwater is generally replenished by the surface, so waterproof and drainage measures need to be taken on the slope. Therefore, two measures are considered: one is to set intercepting ditch around the slope according to the shape of the slope; The second is to set a drainage ditch on the sloping platform.

5.2 shotcrete protection

Slope shotcrete can be divided into ordinary shotcrete, hanging mesh shotcrete and steel fiber shotcrete. Sprayed concrete is suitable for strongly weathered rock slopes; Multi-step high slope formed by pre-splitting smooth blasting of deep cutting; The clayey rock slope with good diagenesis can also be reinforced by bolting and shotcreting.

5.3 Slope lattice protection

Lattice reinforcement technology is a kind of slope reinforcement technology which uses mortar rubble, cast-in-place reinforced concrete or precast prestressed concrete to protect slope surface and fix it with anchor rod or anchor cable. The main function of the lattice is to distribute the residual sliding force, earth pressure and rock pressure of the slope to the anchor rod or anchor cable at the lattice node, and then transfer them to the stable stratum through the anchor cable, so that the slope is in a stable state under the anchoring force provided by the anchor rod or anchor cable. The slope lattice reinforcement technology has the advantages of flexible layout, various lattice forms, convenient section adjustment and close contact with slope surface. It can strike along the slope, and the frame can be protected by hanging nets, planting grass and spraying concrete, or reinforced by cast-in-place concrete slabs.

5.4 Slope vegetation protection

Slope vegetation protection can be divided into vegetation protection, soil slope vegetation protection and rock slope vegetation protection. The function of vegetation slope protection is mainly reflected by the mechanical effect and hydrological effect of vegetation; At present, there are mainly the following vegetation protection technologies for soil slopes: ① stepped vegetation; (2) Frame vegetation; ③ hole sowing or furrow sowing; ④ Hydraulic jet; ⑤ Vegetation belt; ⑥ Greening net; ⑦ Geonet mat. Rock slope is different from soil slope, and the commonly used vegetation slope protection methods can not be applied to rock slope. Thick-layer substrate spraying vegetation slope protection technology solves the problem that plants can't grow on rock slopes by spraying a layer of grass-roots material which is similar to natural soil structure and can store water and conserve.

Concluding remarks

Due to the complex topographic and geological conditions, landslide and high slope engineering have always been the main engineering geological problems in railway and highway construction in mountainous areas. Therefore, strengthening the research on landslide and high slope disease prevention is not only of great significance to the coordinated development of highway traffic infrastructure construction and ecological environment protection in plateau mountainous areas, but also will play a positive role in promoting the development of geological disaster prevention theory and prevention technology in China.

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