CN110258589B

CN110258589B - Ecological slope protection structure for preventing and treating slump of expansive soil slope and construction method

Info

Publication number: CN110258589B
Application number: CN201910486465.5A
Authority: CN
Inventors: 江学良; 张继琪; 宁远思; 王聚山; 李涛; 肖宏彬; 尹健
Original assignee: Central South University of Forestry and Technology; Chongqing Railway Hub East Ring Line Construction Headquarters of China Railway Chengdu Group Co Ltd
Current assignee: Central South University of Forestry and Technology; Chongqing Railway Hub East Ring Line Construction Headquarters of China Railway Chengdu Group Co Ltd
Priority date: 2019-06-05
Filing date: 2019-06-05
Publication date: 2021-07-20
Anticipated expiration: 2039-06-05
Also published as: CN110258589A

Abstract

The invention discloses an ecological slope protection structure for preventing and treating slump of an expansive soil side slope and a construction method, wherein the ecological slope protection structure comprises an anti-slip anti-seepage belt, a waterproof geomembrane, vetiver grass, slope protection turf and a drainage ditch; the anti-skid and anti-seepage belt is arranged in a slope body of a side slope, is formed by drilling and grouting cement mortar at a stagnant water position or a potential sliding surface in the slope and is of a continuous concave curved surface structure; the waterproof geomembrane is covered on the slope surface, the slope top and the slope foot, the waterproof geomembrane is provided with holes, vetiver grass is planted in the holes, the upper surface of the waterproof geomembrane is covered with soil, and slope protection turf is planted on the soil; the drainage ditch sets up in side slope toe department. An anti-slip and anti-seepage belt formed by pouring cement mortar through a drill hole, a degradable waterproof geomembrane covered on a slope surface and vetiver grass planted in the slope body form a closed ecological water circulation system; the transpiration of the vetiver stems and leaves and the water retention of developed roots are utilized to control the water content of the side slope within a certain range, so that the effect of controlling the landslide of the expansive soil side slope of the highway is achieved.

Description

Ecological slope protection structure for preventing and treating slump of expansive soil slope and construction method

Technical Field

The invention belongs to the field of slope engineering, and particularly relates to an ecological slope protection structure for preventing and treating slump loss of an expansive soil slope and a construction method.

Background

The landslide of the expansive soil side slope of the highway belongs to shallow landslide, the depth of a sliding surface is generally less than 4-5 m, and the expansive soil side slope has the treatment problems of skidding when meeting a moat, skidding when building, and repeated skidding. At present, slope cutting and unloading technology, slope surface protection technology, rigid retaining technology and the like are common for the treatment technology of the landslide of the expansive soil side slope. The slope cutting and unloading technology increases the occupied land of slope cutting and soil abandoning, so that water and soil loss and environmental pollution are caused, and slump still occurs after the slope is released to a smaller slope; the slope protection technology can only prevent and control rain wash, cannot provide enough retaining force, is easy to damage under the action of dry and wet circulation, and has large post-maintenance engineering quantity; the rigid retaining technology is difficult to construct, long in construction period and high in manufacturing cost, the retaining soil body is not allowed to deform, and the retaining upper soil body cannot slide downwards. The slope protection technology has single structural form and poor mechanical stability, and can not flexibly select proper ecological slope protection structural types by combining with specific construction sites according to local conditions.

Disclosure of Invention

The invention aims to provide an ecological slope protection structure for preventing and treating slump of an expansive soil side slope and a construction method.

The ecological slope protection structure for preventing and treating the slump of the expansive soil side slope comprises an anti-slip and anti-seepage belt, a waterproof geomembrane, vetiver grass, slope protection turf and a drainage ditch; the anti-skid and anti-seepage belt is arranged in a slope body of a side slope and is formed by drilling and grouting cement mortar at a stagnant water position or a potential sliding surface in the slope, and the anti-skid and anti-seepage belt is of a continuous concave curved surface structure;

the waterproof geomembrane is covered on the slope surface, the slope top and the slope foot, holes are formed in the waterproof geomembrane, the vetiver grass is planted in the holes, soil covers the upper surface of the waterproof geomembrane, and the slope protection turf is planted on the soil;

the drainage ditch is arranged at the toe of the side slope;

the waterproof geomembrane and the anti-slip anti-seepage belt form effective lap joint to form a closed structure together for preventing rainwater from seeping downwards; the vetiver grass and the slope surface turf in the slope are used for controlling and adjusting the water content in the slope; the drainage ditch is used for draining the collected rainwater.

Preferably, the upper end of the anti-sliding and anti-seepage belt is connected with the horizontal table top at the top end of the side slope, and the lower end of the anti-sliding and anti-seepage belt is connected with the bottom end of the side slope.

Preferably, the upper surface of the waterproof geomembrane is covered with 5-7 cm of soil.

The invention also provides a construction method of the ecological slope protection structure for preventing and treating the slump of the expansive soil side slope, which comprises the following steps:

(1) after an earth side slope is excavated and formed, cement mortar is poured into a stagnant water position (or a potential sliding surface) in the slope to construct an anti-skid and anti-seepage belt;

(2) after soil preparation is carried out on the side slope, a drainage ditch and a horizontal table top are built, a slope surface, a slope top and a slope foot are covered with a waterproof geomembrane, and the waterproof geomembrane and the anti-slip anti-seepage belt form effective lap joint to form a closed structure together;

(3) planting vetiver grass seedlings at the positions of the reserved holes of the waterproof geomembrane;

(4) after vetiver grass is planted, soil is covered on the side slope surface waterproof geomembrane, and slope protection turf is laid.

Further, in the step (1), the strength of the cement mortar in the anti-slip and anti-seepage belt is C20 grade, so that the slope is prevented from integrally slipping to strengthen the stability of the slope, and meanwhile, the precipitation and the infiltration of water in the slope are prevented.

Further, in the step (2), the land preparation is performed on the side slope, specifically:

a) on a side slope with the gradient less than 15 degrees and a thicker soil layer, a strip soil preparation mode is adopted, soil is properly turned deeply, and therefore the growth of vetiver grass is promoted;

b) adopting a contour line strip land preparation mode at a place with a gradient of 15-25 degrees, namely roughly preparing terrace type strip small planes on the side slope along the contour line direction, wherein the land preparation depth is 30 cm;

c) in the slope area with the gradient larger than 25 degrees, a hole-shaped land preparation mode is adopted, and the land preparation specification is 30cm multiplied by 30cm (length multiplied by width multiplied by depth).

Further, in the step (2), the waterproof geomembrane is made of a degradable plastic film.

Further, in the step (3), the vetiver grass seedlings are annual seedlings which are just cut and do not spike and flower, the stubble height is 20-30 cm, the root system is developed, and the seedlings are transported with bags to reduce the water loss of the plants.

The vetiver grass seedling is planted from middle March to middle March every year, the overground part is reserved for 15-25 cm during planting, and the root system is cut to 7-12 cm.

Further, in the step (3), the vetiver grass seedlings are planted in a ridge mode, a ridge of vetiver grass is planted along the slope in a direction perpendicular to the direction of the slope at intervals of 30cm, the ridge width is 20cm, the ridge spacing and the planting spacing are both 30cm, and the burial depth is 10-15 cm.

The expansive soil slope can be properly densely planted in areas with relatively average sufficient annual rainfall, and properly sparsely planted in areas with relatively small annual rainfall and uneven distribution, so that the entire expansive soil slope is in a water loss-water retention good state on the basis of considering the characteristics of expansive soil, the biological action of vetiver grass and the local hydrological conditions, the water content in the expansive soil is controlled within a certain range, and the soil fixation effect of developed root systems of vetiver grass is utilized to ensure that the expansive soil slope does not disintegrate in dry seasons and does not slide and slump in rainy seasons.

The ecological slope protection structure is suitable for the expressway expansive soil slope with a slow slope gradient, a low slope height and a shallow slope potential sliding surface, and is particularly suitable for the areas with humid climate and annual precipitation of 500-6000 mm and suitable for the growth of vetiver grass.

The anti-slip impermeable belt can increase the shear resistance of a soil layer at the stagnant water position of a slope body, prevent the side slope from generating integral landslide due to the existence of a stagnant water layer, reduce the infiltration of water and atmospheric precipitation in the side slope and create a growth environment with sufficient water for vetiver grass.

Planting vetiver grass and laying the turf at domatic slope after side slope soil preparation and covering waterproof geomembrane, it prevents inside a large amount of precipitation infiltration slope body simultaneously to reduce slope body moisture and give off, and most precipitation is through domatic and escape canal drainage side slope to prevent that vetiver grass from forming the slope protection effect front side slope and receive the rainwash, and reduce rainwater infiltration control slope body moisture content, prevent that inflation soil from meeting water inflation and leading to the side slope landslide.

Most of rainfall permeating into the slope in rainy season is isolated by the slope surface turf and the waterproof geomembrane in the whole slope protection system from entering the slope, the rainfall permeating into the slope is discharged out of the slope body under the transpiration effect of the vetiver grass, and the developed root system of the vetiver grass can effectively keep the moisture of the slope body in dry seasons, so that the water content of the slope is controlled and automatically adjusted, and the characteristics of water swelling and water loss shrinkage of expansive soil are effectively inhibited; in addition, developed roots of vetiver grass are wound and overlapped in the slope body, so that the shear strength of the soil body is improved, the distribution of water in the soil body is balanced, and the stability of the slope is maintained.

The beneficial technical effects of the invention are as follows:

in the ecological slope protection structure for preventing and treating the slump of the expansive soil side slope, the root system of the vetiver can reach 6m at the longest, the requirement of treating the expansive soil side slope of the highway can be met, the transpiration and the root water retention of the vetiver are the core of a prevention and treatment system, the anti-skid impervious belt is the foundation of the prevention and treatment system, and the slope turf and the drainage ditch are important auxiliary measures. According to the related research of the expansive soil side slope, a water retaining layer exists in the expansive soil side slope with a relatively slow slope, and the existence of the water retaining layer is an important reason for the slump of the expansive soil side slope, so that the anti-slip and anti-seepage strip has the function of preventing the whole slump of the side slope and simultaneously preventing water from seeping downwards. The slope surface turf greening and waterproof geomembrane construction ensures that most of rainfall is discharged from the slope surface, the vetiver grass discharges excessive moisture of a slope body through transpiration in rainy season, and the water content of the slope is kept in a certain range through a developed root system in dry season, so that the expansive soil slope body reaches a good water loss-retention balance state, and the slope body does not disintegrate in dry season and does not slump in rainy season.

According to the invention, a closed ecological water circulation system is formed by drilling and pouring an anti-slip and anti-seepage belt made of cement mortar, a degradable waterproof geomembrane covered on a slope surface and vetiver planted in the slope body; the water content of the side slope is controlled within a certain range by utilizing the transpiration effect of the stems and leaves of the vetiver grass and the water retention effect of developed roots, the swelling and shrinking characteristics of expansive soil of the side slope of the highway are controlled, and the stability of the side slope is improved by utilizing the mechanical reinforcement effect of the developed roots of the vetiver grass; the ecological automatic adjustment of the water in the expansive soil side slope body of the highway is realized, and the effect of controlling the slump of the expansive soil side slope of the highway is achieved.

The construction method has simple process, lower cost compared with other slope protection methods, environment beautification, ecology and environmental protection, strong adaptability and easy popularization.

Drawings

Fig. 1 is a schematic sectional view of an ecological slope protection structure for prevention and control of the slump of an expansive soil side slope of a highway.

FIG. 2 is a schematic cross-sectional view of a vetiver planting method.

FIG. 3 is a schematic view of a planting slope of vetiver grass.

Detailed Description

The invention is further illustrated below with reference to specific embodiments and the accompanying drawings.

The invention provides an ecological slope protection structure for preventing and treating the landslide of an expansive soil side slope of a highway, which comprises an anti-slip and anti-seepage belt, a waterproof geomembrane, vetiver grass, slope protection turf and a drainage ditch as shown in figure 1;

the anti-slip impermeable belt is arranged in a slope body of the side slope and is formed by punching and grouting cement mortar at a stagnant water position in the slope, the anti-slip impermeable belt is of a continuous concave curved surface structure, the upper end of the anti-slip impermeable belt is connected with a horizontal table top at the top end of the side slope, and the lower end of the anti-slip impermeable belt is connected with the bottom end of the side slope;

the waterproof geomembrane is covered on the slope surface, the slope top and the slope foot, the waterproof geomembrane is provided with holes, vetiver grass is planted in the holes, the upper surface of the waterproof geomembrane is covered with soil, and slope protection turf is planted on the soil;

the drainage ditch is arranged at the toe of the side slope;

The construction method of the ecological slope protection structure for preventing and treating the landslide of the expansive soil side slope of the highway comprises the following steps of:

step 1: building double rows of supports on an excavated and formed expansive soil slope by using phi 42mm steel pipes, installing a down-the-hole drill by using a support platform to manually cooperate with the drill to drill holes, wherein the reference contour line can perform investigation and drilling at intervals of 2m, and excessive intensive drilling is not performed, in the implementation process, the drilling depth is adjusted according to the position of a sliding surface of a potential slope, the position of a stagnant water layer or the sliding surface is finally determined, a grouting test is performed in an actual slope, the maximum grouting pressure is determined, the actual grouting pressure should not exceed the maximum grouting pressure, and C20 cement mortar is poured by using the drill holes to form an anti-slip and anti-seepage zone;

step 2: before vetiver grass is planted, leveling work needs to be carried out on a slope surface, on one hand, the slope gradient can be properly slowed down, on the other hand, stones which are easy to slip off the slope surface are removed to eliminate potential safety hazards, on the slope with the gradient smaller than 15 degrees and the thick soil layer, a strip soil preparation mode is adopted, soil is properly turned deeply to promote growth of vetiver grass, after soil preparation is carried out on the slope, a drainage ditch and a horizontal table surface are built, the horizontal table surface is convenient for fertilization and planting operation, slope runoff is intercepted at the same time, and water storage and water retention are facilitated; the drainage ditch has the functions of preventing the slope from erosion and reasonably organizing and constructing by combining the watershed and catchment area positions of the side slope on the spot;

after the slope surface is leveled and the auxiliary construction is completed, soil is removed according to local conditions according to different slope surface conditions: the common road side slope has poor geological conditions, thin slope soil layer, large sand content and poor plant growth environment, and the vetiver grass is not directly contacted with rocks during planting by combining soil dressing and soil improvement on the basis of scientific soil preparation, so that a suitable soil environment for the seedling growth of the vetiver grass is created as far as possible. The depth of a soil layer of the soil slope is more than 20cm, the content of sand and stone is less, and the vetiver grass is suitable for being directly planted; if the content of sand and stone is 30-50%, the soil body is loose in a section with a poor soil structure, local collapse is easy to occur, the water and fertilizer retention capacity is weak, a circular slope is adopted for grooving, and a proper amount of additional soil is arranged in the groove; the soil structure of the rocky side slope is extremely poor, the content of sand and stone is more than or equal to 50%, some places even mother rocks are always exposed, a circular slope is adopted for grooving, then soil is removed in the groove, and after soil preparation and soil removal are completed, a waterproof geomembrane is covered on the slope;

and step 3: reserving holes at planting points of vetiver grass, filling soil in the holes during planting to enable soil bodies at the holes to be 10cm higher than a slope surface, so that geomembranes can be covered easily and growth of the vetiver grass can be guaranteed, as shown in figure 2, an overlapping area with the length of 10cm is reserved at a contact position between adjacent waterproof geomembranes, meanwhile, drainage ditches are built at the slope feet of the side slope by referring to local annual precipitation, atmospheric precipitation discharged through the slope surface is discharged quickly, and erosion of the side slope by rainwater is reduced;

before planting vetiver grass, necessary material preparation is needed, including preparation of vetiver grass seedlings, fertilizers, irrigation water, drought-resisting shading materials and the like, wherein the vetiver grass seedling quality is guaranteed by adopting annual and just cut seedlings which have developed root systems and are not spiked and blossomed, and the vetiver grass seedlings are planted from middle of March to middle of April every year. And (3) reserving 20-30 cm of overground part during planting, and cutting the root system to 10-15 cm. During transportation, the plants are transported by bags to reduce the water loss of the plants, and after the plants are planted, root fixing water is sprayed in time; in addition, in order to prevent moisture from dispersing and burning seedlings in the stacking process, materials such as drought resistance, shading and the like need to be prepared;

the vetiver grass is planted in a ridge mode, a ridge is planted in the direction of slope inclination and every 30cm, the direction of the ridge is perpendicular to the direction of the slope, the width of the ridge is 20cm, the buried depth is 10-15 cm, and during planting, the roots of the vetiver grass are kept flat and are not bent or coiled. The method has the advantages that the method can be used for properly close planting in areas with relatively average and sufficient annual precipitation, and properly thinning planting in areas with relatively small annual precipitation and uneven distribution, and achieves the good water loss-retention state of the whole expansive soil slope on the basis of considering the characteristics of expansive soil, the transpiration effect and the root water retention effect of vetiver grass and the local hydrological conditions;

and 4, step 4: after planting, the vetiver grass is intensively watered and appropriately shaded, soil is covered on the slope surface for 5-7 cm after planting, turf is laid, the turf and a waterproof geomembrane work together to reduce rainwater infiltration, a shading net is additionally arranged, watering and moisture preservation are carried out every other day, the shading net is collected for multiple times in stages after the vetiver grass turns green and grows, manual auxiliary watering is combined within 1 month after planting, watering is carried out for 1-2 times every week to help the vetiver grass seedlings to pass through a water-requiring period, additional fertilization is carried out for 3 times in time besides the reinforced watering work, withered branches and leaves are cut off in winter, the slope surface is covered on the ground, the water and soil are kept well, the fertilizer can be used, fertilizer, water and insect pest management are paid attention to the later-stage management of the vetiver grass, and fig. 3 is a schematic diagram of the slope surface after planting of the vetiver grass in the embodiment.

The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above embodiments, and it should be understood that modifications and changes by those skilled in the art without departing from the technical idea of the present invention should be regarded as the scope of the present invention.

Claims

1. An ecological slope protection structure for preventing and treating slump of an expansive soil side slope is characterized by comprising an anti-slip and anti-seepage belt, a waterproof geomembrane, vetiver grass, slope protection turf and a drainage ditch, wherein the anti-slip and anti-seepage belt is arranged in the side slope body and is formed by drilling and grouting cement mortar at a stagnant water position or a potential sliding surface in the slope, the anti-slip and anti-seepage belt is of a continuous concave curved surface structure, the upper end of the anti-slip and anti-seepage belt is connected with a horizontal table top at the top end of the side slope, and the lower end of the anti-slip and anti-seepage belt is connected with the bottom end of the side slope;

the waterproof geomembrane covers the slope surface, the slope top and the slope foot, holes are formed in the waterproof geomembrane, the vetiver grass is planted in the holes, the upper surface of the waterproof geomembrane is covered with 5-7 cm of soil, and the slope protection turf is planted on the soil;

the drainage ditch is arranged at the toe of the side slope;

2. The construction method of the ecological slope protection structure for preventing and treating the slump of the expansive soil slope according to claim 1, which is characterized by comprising the following steps:

(1) after the earth side slope is excavated and formed, cement mortar is poured at the stagnant water position or the potential sliding surface in the slope to construct an anti-skid and anti-seepage belt;

3. The construction method of an ecological slope protection structure for preventing and treating slump of an expansive soil slope according to claim 2, wherein in the step (1), the strength of cement mortar in the anti-slip and anti-seepage belt is C20 grade.

4. The construction method of the ecological slope protection structure for preventing and treating the slump of the expansive soil slope according to claim 2, wherein in the step (2), soil preparation is performed on the slope, and specifically comprises the following steps:

5. The construction method of an ecological slope protection structure for preventing and treating slump of an expansive soil slope according to claim 2, wherein in the step (2), the waterproof geomembrane is a degradable plastic film.

6. The construction method of the ecological slope protection structure for preventing and treating the slump of the expansive soil slope, as claimed in claim 2, wherein in the step (3), the vetiver grass seedlings are annual and freshly mowed seedlings which do not slip and flower, the stubble height is 20-30 cm, the root system is developed, and the seedlings are transported with bags during transportation to reduce the water loss of the plants.

7. The construction method of the ecological slope protection structure for preventing and treating the slump loss of the expansive soil slope, as claimed in claim 2, is characterized in that in the step (3), the vetiver seedlings are planted in ridges, a ridge of vetiver is planted in the direction perpendicular to the trend of the slope at intervals of 30cm along the slope trend, the ridge width is 20cm, the ridge spacing and the planting spacing are both 30cm, and the burial depth is 10-15 cm.