CN104164883B - A kind of loose unsaturated soil side slope superficial again compacting in conjunction with vegetative coverage means of defence - Google Patents

Abstract

The invention discloses a protective method for re-compacting the shallow layer of loose unsaturated soil slope combined with vegetation covering. Excavate the 2-3m thick loose residual soil or slope accumulation soil below the slope surface, and set up a number of drainage blind ditches along the slope at equal intervals for 1/3-1/2 of the slope length from the slope foot. They are all connected to the drain holes of the retaining wall at the foot of the slope; the excavated loose residual soil or slope accumulation soil is layered and compacted to a compaction degree of more than 90%, that is, the re-compacted covering layer is formed; the top of the re-compacted covering layer Lay nutrient soil with a thickness of 0.15-0.3m, and plant dwarf vegetation. The invention can effectively reduce rainfall infiltration, control the height of the soaking line at the bottom of the slope, maintain the suction in unsaturated soil, increase the shear strength of the soil, enhance the overall stability of the slope, and effectively prevent shallow sliding of the loose unsaturated soil slope. The slope protection method involved in the invention can obtain local materials, is easy to construct, has low cost, strong practicability, and has good ecological restoration effect.

Description

A protective method for loose unsaturated soil slope shallow layer recompaction combined with vegetation coverage

technical field

The invention relates to a slope surface protection method for soil slopes, in particular to a protection method for loose unsaturated soil slope shallow layer recompaction combined with vegetation coverage.

Background technique

The weathered residues of igneous rocks, strong earthquakes in Southwest China, dumping of tailings and excavation of engineering construction have formed a large number of loose unsaturated soil slopes, which are affected by the infiltration of heavy rainfall in summer, and landslides occur from time to time. This type of rainfall-induced landslide has a shallow layer Sliding, large quantity and wide range of features. The slope protection measures of the current national standards for soil slopes mainly include: masonry slope protection and face protection wall, sash, hammer face, etc. The main material of masonry slope protection and face protection wall is flake or block stone, which can be divided into two construction methods: dry laying and mortar laying. It is suitable for soil slopes that are prone to surface water erosion in areas rich in stone. The frame protection adopts concrete, mortar block (block) stone, egg (gravel) stone, etc. as the skeleton, and plants should be planted in the frame or other auxiliary protection measures should be adopted. Surface hammering protection is to spread the compound soil, tetra compound soil or cement slag mixed soil on the slope surface, and manually compact it to form a closed anti-seepage layer. It is suitable for soil slopes with a slope less than 1:0.5 that are easy to be washed by rain. The above protection measures require a large amount of external materials such as stone and cement, and the formed slopes are difficult to be greened and ecologically restored. Moreover, as time goes by, mortar masonry, concrete, and composite soil are susceptible to aging and even damage due to rain and weathering. Later maintenance and remediation costs are high. Therefore, environmental protection and more durable protection technology is required in engineering, especially for a large number of loose soil slopes.

Contents of the invention

In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a method for recompacting the shallow layer of loose unsaturated soil slope combined with vegetation coverage protection method. Improve the anti-seepage performance of loose soil by shallow recompaction to reduce the amount of water infiltrated into the slope during rainfall. The evapotranspiration of the vegetation layer in sunny days helps to drain the infiltrated water, and control it through the blind drainage ditch along the slope The height of the infiltration line at the lower part of the slope. The combination of the above three measures can effectively maintain the unsaturated soil suction and shear strength of the slope, maintain the stability of the slope and the durability of the slope, and achieve a good greening effect.

The technical scheme step that the present invention adopts is as follows:

Step 1) Excavate the 2-3m thick loose residual soil or slope accumulation soil below the slope surface, and set up multiple drainage blind ditches along the slope direction at equal intervals for 1/3-1/2 of the slope surface length from the slope foot , the blind ditches are connected with the drain holes of the retaining wall at the foot of the slope;

Step 2) is to compact the loose residual soil or slope soil excavated in step 1) layer by layer to a compaction degree of more than 90%, that is, to form a re-compacted covering layer;

Step 3) is to lay a vegetation layer with a thickness of 0.15-0.3m on the re-compacted covering layer of step 2).

The multiple blind drainage ditches along the slope are each 0.3-0.5m in thickness and 0.5-1m in width, the distance between two adjacent blind drainage ditches along the slope is 5-10m, and the filling particle size inside the blind ditch is 20 - 60mm pebbles or crushed stones with a mud content of less than 1%, lined with woven geotextiles.

The virtual paving thickness of each layer is 0.3-0.4m when the loose residual soil or slope soil is compacted in layers.

The diameter of the drain hole of the retaining wall at the foot of the slope is 0.05-0.1m.

The beneficial effects that the present invention has are:

1. Through the combined effects of shallow recompaction, vegetation coverage, and drainage blind ditch along the slope, rainfall infiltration can be effectively reduced, the height of the infiltration line at the lower slope can be controlled, and the suction and shear strength of the unsaturated soil can be maintained. Effectively prevent shallow sliding of loose soil slopes.

2. Most of the materials for the re-compacted cover layer, vegetation layer and blind drainage ditch along the slope can be obtained locally, and the natural materials used have good durability.

3. The technology is easy to construct, low in cost and strong in practicability.

4. The slope protection method conforms to the concept of greening and environmental protection, and has a good ecological restoration effect.

Description of drawings

Fig. 1 is a schematic cross-sectional view of a specific structure of the present invention.

Fig. 2 is a view along the direction A of Fig. 1 .

Fig. 3 is the construction sequence of the partition partition of the present invention.

In the figure: 1. Water intercepting ditch at the top of the slope, 2. Loose residual soil or slope accumulation soil, 3. Re-compacted covering layer, 4. Drainage blind ditch along the slope direction, 5. Lined with textile geotextile, 6. Vegetation Layer, 7. The weep hole of the retaining wall at the foot of the slope.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Fig. 1 and Fig. 2, after the present invention excavates the loose residual soil or slope accumulation soil 2 below the slope surface 2-3m thick, the slope surface length of 1/3-1/2 upwards from the bottom of the slope is equally spaced. A plurality of drainage blind ditches 4 along the slope are set, and the blind ditches 4 are all connected with the discharge holes 7 of the retaining wall at the slope foot, and a slope top intercepting ditch 1 parallel to the slope foot retaining wall is provided on the top of the slope;

Step 2) is to compact the loose residual soil or slope accumulation soil 2 excavated in step 1) layer by layer to a compaction degree of more than 90%, that is, to form a re-compacted covering layer 3;

Step 3) is to lay nutritious soil with a thickness of 0.15-0.3m on the re-compacted cover layer 3 of step 2) and plant dwarf plants to form a vegetation layer 6, which is suitable for local climate conditions and has good erosion resistance grass or dwarf shrubs.

The plurality of drainage blind ditches 4 along the slope are each 0.3-0.5m in thickness and 0.5-1m in width, and the distance between two adjacent blind drainage ditches 4 along the slope is 5-10m, and the filling particle size inside the blind ditches is 20-60mm pebbles or crushed stones with a mud content of less than 1%, lined with woven geotextiles5;

The virtual paving thickness of each layer is 0.3-0.4m when the loose residual soil or slope accumulation soil is compacted in two layers.

The diameter of the drain hole 7 of the retaining wall at the foot of the slope is 0.05-0.1m.

Protection method principle of the present invention is such:

By excavating and compacting the loose residual soil or slope accumulation soil 2 2-3m below the slope surface, the compactness is increased and the porosity of the shallow loose residual soil or slope accumulation soil 2 is reduced. The effects of recompaction treatment include two aspects: one is to reduce the permeability coefficient of the shallow loose soil, and the permeability coefficient of the recompacted cover layer 3 is at least an order of magnitude lower than that of the original loose residual soil or slope accumulation soil 2, so it is significantly When reducing rainfall, rainwater infiltrates into the slope, and most of the rainfall is converted into surface runoff. The reduction of rainfall infiltration helps to maintain the suction and shear strength of the unsaturated soil of the slope, and effectively reduces the impact of rainfall on the stability of the shallow soil of the slope. Adverse effects; Second, the integrity and shear strength of the shallow loose soil are improved through excavation and re-compaction, and the stability of the shallow soil of the slope is further improved. The slope vegetation layer 6 plays the role of maintaining water and soil during rainfall and avoiding excessive scouring of the slope; after the rainfall stops, the vegetation layer 6 continuously dries up the water infiltrated in rainy days through evapotranspiration, so that the rainfall infiltrates to form shallow soil The suction loss is restored, thereby eliminating the adverse effects of rainfall on the stability of the slope's shallow soil. The blind drainage ditch 4 along the slope direction laterally drains the water accumulated at the foot of the slope to the weep hole 7 of the retaining wall at the foot of the slope, controls the height of the infiltration line at the bottom of the slope, and effectively solves the problem of local instability at the foot of the slope. Through the combined effect of the above three measures, the amount of water infiltrated into the slope during rainfall can be effectively reduced, and the suction of the slope soil can be kept greater than the critical suction corresponding to water absorption and softening damage, so as to maintain the stability of the slope and the durability of the slope, and achieve good greening Effect.

As shown in Fig. 1, Fig. 2 and Fig. 3, the implementation mode of the present invention: select construction in dry season, construct in intervals along the slope from left to right, excavate from top to bottom in a single construction area, and press from bottom to top Real, as shown in Figure 3. For side slopes with long slopes, a single block shall be constructed in sections, and horse trails shall be set between adjacent sections. Specific construction methods in the selected construction area: (1) A slope top intercepting ditch 1 parallel to the retaining wall at the slope foot is provided on the slope top; Soil or slope accumulation soil 2 shall be excavated from top to bottom and accumulated in the temporary soil accumulation area for standby; (3) Level the excavation bottom surface of the excavation construction area, and further dig down 0.3-0.5m at the position of drainage blind ditch 4 along the slope Deep trenches, filled with pebbles or gravels with a particle size of 20-60mm, and lined with woven geotextiles 5, that is, to form blind drainage ditch 4 along the slope; (4) the excavated in (1) Backfill loose residual soil or slope accumulation soil 2, and compact layer by layer from bottom to top to a compaction degree above 90%, forming a re-compacted covering layer 3; (5) Excavate temporary soil piles according to the requirements in (1) area, the excavated loose residual soil or slope accumulation soil 2 is accumulated on the re-compacted cover layer 3 in the excavation construction area; (6) the temporary soil accumulation area shall be constructed according to the requirements of (3) and (4), Lay nutrient soil and plant grass or dwarf shrubs on the re-compacted cover layer 3 in the construction area to form the vegetation layer 6; (7) excavate the unexcavated area according to the requirements in (1), and the loose residual soil or The slope accumulation soil 2 is accumulated on the re-compacted overburden layer 3 in the temporary soil accumulation area, and the follow-up construction will be carried out gradually according to the above requirements, and will not be repeated here.

The purpose and effects of the present invention will become more apparent by describing the present invention in detail according to the accompanying drawings and embodiments.

Example 1

A residual soil high-fill embankment located in the Nanping section of the Beijing-Fuzhou Expressway. The soil layers below the slope of the embankment are: 5 m thick loose loamy soil, 2.6 m thick gravel soil, 2.6 m thick sandy cohesive soil, 1.8 m thick fragmented strongly weathered fine sandstone and 1.8 m thick weakly weathered fine sandstone. The construction quality of the residual soil embankment is poor, the degree of compaction is low, and the shallow fill of the slope is in a loose state. The project is located in a humid climate zone, and the heavy rainfall in summer has caused the embankment slopes of some road sections to become unstable and slide, seriously affecting the safety of the embankment.

The control method of the present invention is used to control the side slope of the residual soil embankment. The 3m thick loose loamy soil below the slope surface shall be excavated from top to bottom along the slope surface, and the stones shall be picked out and stacked separately during the excavation process for filling the drainage blind ditch. Along the road direction, set up-slope drainage blind ditches at intervals of 10m. The blind ditches are excavated upward from the foot of the slope. The length is 1/2 of the slope length, the depth is 0.5m, and the width is 1m. For stones, stones with a particle size greater than 60mm are crushed and then filled, and the mud content is controlled to be less than 1%. After the blind ditch is filled, it is lined with a woven geotextile as a reverse filter layer. A 2m high masonry retaining wall is built at the foot of the slope, and the lower part of the retaining wall is provided with a drain hole which is connected with the drainage blind ditch along the slope. The diameter of the drain hole is 0.1m. The excavated loose loamy soil shall be backfilled and compacted layer by layer, and the degree of compaction shall not be less than 90%, and the virtual paving thickness of each layer shall be 0.3m during layer compaction. On top of the compacted covering layer, 0.15m of nutrient soil is spread and Bermudagrass is planted to form a vegetation layer. After the treatment, the stability of the embankment slope has been significantly improved. It has been tested by many years of heavy summer rainfall, and no instability or damage has occurred.

Example 2:

It is located in a granite residual soil road cutting in the Jiangxi Liren-Longnan section of the Daqing-Guangzhou Expressway. From top to bottom, the cutting slope soil layers are: 0.5m thick cultivated soil, 2m thick gravel-containing silty clay formed by weathering of granite, and thicker crushed fully weathered granite. The shallow cultivated soil and gravel-containing silty clay of the slope are loose and unsaturated soil with strong water permeability, and unstable landslides are prone to occur under heavy rainfall conditions.

The control method of the present invention is used to treat the residual soil cutting slope. The shallow 2.5m cultivated soil and gravel-containing silty clay are excavated from top to bottom along the slope, and the excavated cultivated soil is piled up separately for laying the nutrient soil layer. During the excavation process, the stones will be picked out and stacked separately for filling in the drainage blind ditch. Along the road direction, blind drains along the slope are set at equal intervals of 5m. The blind drains are excavated upwards from the foot of the slope. The length is 1/3 of the slope length, the depth is 0.3m, and the width is 0.5m. The stones produced should be controlled to have a particle size between 35-60m and a mud content of less than 1%. After the blind ditch is filled, it is lined with a woven geotextile as a reverse filter layer. A 1.5m high concrete retaining wall shall be built at the foot of the slope, and a drain hole shall be set at the lower part of the retaining wall and shall be connected with the drainage blind ditch along the slope. The diameter of the drain hole shall be 0.05m. Backfill and compact the excavated silty clay layer by layer, control the degree of compaction to not less than 90%, and the virtual paving thickness of each layer during layer compaction is 0.4m. Then backfill the excavated cultivated soil to a thickness of 0.3m after compaction, and plant Zoysia grass on the backfilled cultivated soil to form a vegetation layer. Through the above-mentioned shallow layer recompaction combined with vegetation cover protection treatment, the stability of the cutting slope is significantly improved, and it has a good greening effect, and has not been unstable for many years of operation.

The above-mentioned embodiments are used to illustrate the present invention, rather than to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention.

Claims (3)

1. A kind of loose unsaturated soil slope shallow layer is compacted again and combines vegetation coverage protection method, and the steps of this method are as follows: Step 1) Excavate the 2-3m thick loose residual soil or slope accumulation soil below the slope surface, and set up multiple drainage blind ditches along the slope direction at equal intervals for 1/3-1/2 of the slope surface length from the slope foot , the blind ditches are connected with the drain holes of the retaining wall at the foot of the slope; Step 2) is to compact the loose residual soil or slope soil excavated in step 1) layer by layer to a compaction degree of more than 90%, that is, to form a re-compacted covering layer; Step 3) is to lay nutritious soil with a thickness of 0.15-0.3m on the re-compacted covering layer of step 2), and plant dwarf vegetation; the plurality of drainage blind ditches along the slope, each with a thickness of 0.3-0.5m , the width is 0.5-1 m, the distance between two adjacent drainage blind ditches along the slope is 5-10m, the blind ditch is filled with pebbles or gravel with a particle size of 20-60mm, the mud content is less than 1%, and the outer lining is textile Geotextiles. 2. A kind of loose unsaturated soil slope shallow layer recompaction combined with vegetation cover protection method according to claim 1, characterized in that: the virtual paving thickness of each layer is real-time when the loose residual soil or slope accumulation soil is layered and compacted It is 0.3-0.4m. 3. A kind of loose unsaturated soil slope shallow recompaction combined with vegetation cover protection method according to claim 1, characterized in that: the diameter of the drain hole of the retaining wall at the foot of the slope is 0.05-0.1m .