A reinforcing method for wide field filling of a slope containing a weak interlayer

Abstract

The application discloses a reinforcing method for wide field filling of a slope containing a weak interlayer, and steps of the method comprise the following: arranging pipe piles on a construction platform excavated in front of a first field filling boundary before the first field filling is used to carry out foundation treatment; arranging counterweight retaining walls on upper portions of the pipe piles; filling the first field filling above original terrain lines behind the retaining walls; filling a second field filling between the retaining walls and a slope surface of the first field filling in a layered filling manner; and carrying out anchor spray support on a slope surface of the second field filling. The method can effectively reduce a scale of slag of the filling body, reduce a self weight of the filling body, reduce a base stress, and reduce overall settlement. The foam light soil can be used for straight slope filling, and can effectively increase the field filling area. Compared with a combination of an anti-slide pile and an anchor cable in the prior art, the combination of the foam light soil, the deep drainage hole and the pile foundation retaining wall can effectively reduce a construction period, reduce construction difficulty, simplify a construction scheme and reduce engineering investment.

Description

Technical Field

[0001] This invention belongs to the field of hydropower engineering site leveling and slope technology, and particularly relates to a reinforcement method for wide site leveling and filling of slopes containing weak interlayers. Background Technology

[0002] When constructing hydropower projects in the deep mountain canyons of western China, challenges are invariably encountered, including steep terrain, complex geological conditions, limited available temporary construction sites, severe weathering of exposed landforms, and the presence of extensive debris flow deposits, colluvial deposits, and dammed deposits on the surface. Among these, colluvial deposits interbedded with dammed deposits are the most prominent. Dammed deposits are primarily composed of low-liquid-limit clay, which exhibits a plastic state upon contact with water, with its shear strength decreasing by approximately 50% compared to its pre-water state. Therefore, dammed deposits within colluvial interlayers appear as significantly weak interlayers.

[0003] For the reinforcement of slope embankments containing weak interlayers, the main reinforcement method currently is strong support, which uses concrete anti-slide piles and prestressed anchor cables. The specific scheme is as follows: concrete anti-slide piles are installed near the leading edge of the outer natural slope (the anti-slide zone or the front of the main sliding section), and prestressed anchor cables are placed on the piles. Embankment is then constructed behind the piles. The embankment slope is filled to the required elevation at a slope ratio of 1:1.2, and the slope surface is supported by shotcrete and anchor systems, including self-drilling anchors, reinforcing mesh, C25 shotcrete, and drainage holes.

[0004] The above scheme can effectively reinforce the wide-area leveling and filling of weak interlayer slopes, meeting the stability requirements of the slope and site. However, it has the following shortcomings: 1. Due to the large cantilever height of the anti-slide piles, the large height and scale of the backfill behind the piles make it prone to settlement, which places greater demands on the weight of the construction equipment used for site leveling and also limits the application of site leveling; 2. Since the slope of the backfill needs to be sloped, the usable area of ​​the site leveling will be reduced. Calculated based on a backfill height of (<25m), this scheme will reduce the area of ​​the site leveling by about 30%; 3. Using anti-slide piles + prestressed anchor cables requires specialized construction equipment for both anti-slide piles and prestressed anchor cables, making the construction scheme complex, the construction period long, and the investment in this reinforcement method also relatively large.

[0005] Patent application CN116517010A discloses a method for constructing pile foundations and treating dam foundations with thick overburden containing weak interlayers. The method includes: reinforcing with crushed stone piles and reinforcing the weak interlayer within the pile hole, making the weak interlayer a reinforcing layer; drilling through the reinforcing layer within the pile hole and constructing crushed stone piles within the pile hole. This method requires setting crushed stone within the reinforcing ring to form the pile foundation, which increases the construction steps and does not solve the technical problem of reducing the quality of the fill material.

[0006] Patent application CN117846020A discloses a backfill-prefabricated silo support structure and method for constructing elevated ground levels. This method involves installing silo sections layer by layer within the support area and then backfilling them with soil, forming a stepped support area from bottom to top. Horizontal bars are embedded in the backfill in layers to improve the horizontal stability of the support structure and enhance the stability of the backfill. However, this method requires a base plate, which poses significant construction challenges in complex terrain. Furthermore, the backfill material used in this method is mostly waste material with a high mud content and low compaction requirements. Due to the large volume of backfill and the high additional stress on the foundation, this method carries a significant risk of soil settlement.

[0007] Patent application CN113266021A discloses a foamed lightweight soil-silo composite structure for constructing elevated ground levels. The silo structure is used as a retaining part, and the foamed lightweight soil structure is used as a supporting part to construct the elevated ground level. However, this method is suitable for areas with simple geological conditions. The silo structure is shallow and cannot penetrate the boundary of the interlayer. It is not suitable for treating slopes with weak interlayers. If the depth of the silo structure is increased, it is similar to cast-in-place piles, which requires a large investment and is difficult to construct. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a reinforcement method for wide-site leveling and filling of slopes containing weak interlayers.

[0009] The present invention is achieved through the following technical solutions.

[0010] This invention provides a reinforcement method for wide-site leveling and filling of slopes containing weak interlayers, comprising the following steps:

[0011] S1: Before using the first leveling and filling, pipe piles are laid on the construction platform excavated at the leading edge of the first leveling boundary for foundation treatment;

[0012] S2: A counterweight retaining wall is installed on top of the pipe piles;

[0013] S3: Fill the first leveling area behind the retaining wall and above the original terrain line;

[0014] S4: The second leveling slope is constructed by layering between the retaining wall and the first leveling slope, and anchor spraying support is carried out on the second leveling slope.

[0015] Preferably, the first leveling layer is constructed behind the retaining wall with a slope ratio of not less than 1:2.0, and a platform is left at the front edge of each layer.

[0016] Preferably, in step S3, after the first leveling is completed, the construction of wire mesh hanging, shotcrete support and drainage hole setting is carried out in sequence on the first leveling slope, and a filter layer is laid on the finished shotcrete surface.

[0017] Preferably, the filter layer is a polyester long-fiber nonwoven fabric with a basis weight of not less than 350 g / m.

[0018] Preferably, the retaining wall is located at the upper boundary of the weak interlayer, and the top of the pipe pile extends into the retaining wall.

[0019] Preferably, the bottom of the pipe pile extends below the boundary between the overburden and the bedrock.

[0020] Preferably, the second leveling site adopts a vertical slope layered filling method, with a platform left at the front edge of each layer.

[0021] Preferably, in step S4, the second leveling slope is supported by self-drilling anchor bolts, wire mesh reinforcement, and shotcrete.

[0022] Preferably, in step S4, after the anchor spraying support is completed, a deep drainage hole is set on the second leveling slope, and the deep drainage hole extends to the first leveling slope.

[0023] Preferably, the first site leveling is constructed using stone chips, the second site leveling is constructed using foamed lightweight soil or geogrid, and the retaining wall is a concrete retaining wall or a masonry retaining wall.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. This invention utilizes the lightweight and high-strength properties of foamed lightweight soil to reduce the support strength of wide site leveling and filling of slopes containing weak interlayers, effectively reducing the pressure on the foundation and the overall settlement deformation of the site leveling, eliminating the need for high-investment support methods such as cast-in-place piles and prestressed anchor cables, and further reducing project investment.

[0026] 2. Compared with traditional ordinary stone slag which requires large-scale compaction machinery, the foamed lightweight soil used in this invention has the advantages of good mobility and self-compacting properties, and does not require large-scale mechanical vibration and compaction. This further simplifies the construction plan of the filling body, greatly simplifies the construction plan, and shortens the construction period.

[0027] 3. Compared to traditional stone ballast filling which requires slope ratios, foamed lightweight soil has self-supporting characteristics and can be filled with vertical slopes, providing a larger site area within the same land acquisition area. Alternatively, it can reduce the land acquisition area within the same site area.

[0028] 4. In this invention, by adjusting the filling of some ordinary stone slag sites to foamed lightweight soil, the two materials are mixed and polyester non-woven fabric is placed between the two materials, which reduces the amount of foamed lightweight soil and reduces the project investment. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the present invention;

[0030] Figure 2 This is a schematic diagram of the pipe pile and retaining wall structure of the present invention;

[0031] In the diagram: 1-Original topographic line, 2A-Groundwater level, 2B-Weak interlayer, 2C-Weathered gravel soil layer, 2D-Boundary between overburden and bedrock, 3-Filter layer, 4-Pipe pile, 5-Retaining wall, 6A-First site leveling, 6B-Second site leveling, 7-Deep drainage hole. Detailed Implementation

[0032] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0033] Example 1:

[0034] like Figure 1-2 As shown, the original topographic line 1 is located above the weathered gravel layer 2C. The weathered gravel layer 2C is in contact with the upper boundary of the weak interlayer 2B. The groundwater level line 2A is located between the upper boundary and the lower boundary of the weak interlayer 2B. Below the weak interlayer 2B is the weathered gravel layer 2C. Below the weathered gravel layer 2C is the boundary line 2D between the overburden and the bedrock.

[0035] A reinforcement method for wide-site leveling and filling of slopes containing weak interlayers includes the following steps:

[0036] S1: Before filling the first site leveling 6A, excavate a 4-6m construction platform at the front edge of the first site leveling 6A boundary. Place pipe piles 4 on the construction platform for foundation treatment. The retaining wall 5 and pipe piles 4 are placed at the slope toe of the site leveling filling area to support the overall site leveling slope.

[0037] S2: A 3-4m high counterweight retaining wall 5 is installed on top of the pipe pile 4;

[0038] S3: Fill the first leveling area 6A behind the retaining wall 5 and above the original terrain line 1;

[0039] S4: The second leveling 6B is constructed by layered filling between the retaining wall 5 and the first leveling 6A slope, and anchor spraying support is carried out on the second leveling 6B slope.

[0040] The retaining wall 5 is followed by the first site leveling 6A, which is constructed in layers with a slope ratio of 1:1.75-1:2.0. Each layer is 8.0-10.0m high, and a 2m wide platform is left at the front edge of each layer as a horse walkway.

[0041] In step S3, after filling the first leveling 6A, the slope surface of the first leveling 6A is sequentially constructed with wire mesh, shotcrete support and drainage holes. The drainage hole specifications are: ∅50mm, L=3.0m, and the spacing between adjacent drainage holes is 3.0m. A filter layer 3 is then laid on the finished shotcrete surface.

[0042] The filter layer 3 is a polyester long-fiber nonwoven fabric with a basis weight of not less than 350 g / m. Due to the high permeability of the stone slag, the polyester long-fiber nonwoven fabric plays a role in improving drainage and enhancing permeability stability, so a polyester long-fiber nonwoven fabric with a higher basis weight is selected.

[0043] The retaining wall 5 is located at the upper boundary of the weak interlayer 2B, and the top of the pipe pile 4 extends into the retaining wall 5 by 1.5-2m to enhance stability.

[0044] The bottom of the pipe pile 4 extends below the boundary 2D between the overburden and the bedrock.

[0045] Due to the lightweight, high strength and self-supporting properties of foamed lightweight soil 6B, the second site leveling 6B adopts a vertical slope layer filling method, which can effectively increase the site leveling area. The filling height of each layer of the second site leveling 6B is the same as that of the first site leveling 6A, and a 4m wide platform is left at the front edge of each layer as a horse walkway.

[0046] In step S4, the second leveling slope 6B is anchored and shotcreted using self-drilling anchors, reinforcing mesh, and shotcrete. The self-drilling anchors are ∅25, L=6.0m @1.5×1.5m; the reinforcing mesh is ∅8@20cm×20cm; and C25 concrete is shotcreted to a thickness of 10cm. The construction methods of self-drilling anchors, reinforcing mesh, and shotcrete are existing technologies and will not be described in detail here.

[0047] In step S4, due to the slightly permeable nature of the foamed lightweight soil, after the anchor spraying support is completed, a deep drainage hole 7 is set on the slope of the second leveling 6B. The deep drainage hole 7 extends to the first leveling 6A. The specifications of the deep drainage hole 7 are: ∅110mm, L=30.0~35.0m@3.0×3.0m.

[0048] The first site leveling 6A is filled with stone chips, the second site leveling 6B is filled with foamed lightweight soil, the retaining wall 5 is a concrete retaining wall, and the pipe pile 4 is a steel pipe pile. The specifications of the pipe pile 4 are: pipe diameter ∅1108mm, wall thickness 6mm, L=25~30m, and the spacing between adjacent pipe piles 4 is 1.0m.

[0049] The foamed lightweight soil is a porous material composed of cement, soil, water, and foam, and belongs to existing technology. The cement used in the raw materials is PO42.5R grade ordinary Portland cement. The maximum particle size of the raw soil is within 5mm, with a liquid limit of no more than 30% and a plastic limit of no more than 25%. The foam is prepared using a foaming agent, and the specific material mix ratio needs to be designed according to project requirements.

[0050] Example 2:

[0051] A reinforcement method for wide-site leveling and filling of slopes containing weak interlayers is proposed, based on Example 1, except that the second leveling 6B slope surface uses geogrid anchor spraying support. The geogrid is steel-plastic geogrid with a length L=20m and a spacing of 0.5m.

[0052] Example 3:

[0053] A reinforcement method for wide-site leveling and filling of slopes containing weak interlayers is proposed, based on Example 1, except that the retaining wall 5 is a masonry retaining wall, in order to further reduce the project investment.

Claims

1. A reinforcement method for wide-site leveling and filling of slopes containing weak interlayers, characterized in that, Includes the following steps: S1: Before filling the first site level (6A), pipe piles (4) are laid on the construction platform excavated at the front edge of the first site level (6A) boundary for foundation treatment; S2: A counterweight retaining wall (5) is installed on the top of the pipe pile (4); S3: Fill the first leveling area (6A) behind the retaining wall (5) and above the original topographic line (1); S4: The second level (6B) is filled in a layered manner between the retaining wall (5) and the first level (6A) slope, and anchor spraying support is carried out on the second level (6B) slope. The first site leveling (6A) is filled with stone chips, the second site leveling (6B) is filled with foamed lightweight soil, and the retaining wall (5) is a concrete retaining wall or a masonry retaining wall.

2. The reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 1, characterized in that: The retaining wall (5) is followed by the first leveling (6A) with a slope ratio of not less than 1:2.0, and a platform is left at the front edge of each layer.

3. The reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 1, characterized in that: In step S3, after the first leveling (6A) is filled, the first leveling (6A) slope is successively constructed by hanging wire mesh, spraying concrete support and setting drainage holes, and a filter layer (3) is laid on the finished sprayed concrete surface.

4. The reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 3, characterized in that: The filter layer (3) is a polyester long fiber nonwoven fabric with a basis weight of not less than 350g / m.

5. The reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 1, characterized in that: The retaining wall (5) is located at the upper boundary of the weak interlayer (2B), and the top of the pipe pile (4) extends into the retaining wall (5).

6. The reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 1, characterized in that: The bottom of the pipe pile (4) extends below the boundary line (2D) between the overburden and the bedrock.

7. The reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 1, characterized in that: The second leveling (6B) adopts a vertical slope layered filling method, with a platform left at the front edge of each layer.

8. The reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 1, characterized in that: In step S4, the second leveling (6B) slope is supported by self-drilling anchors, wire mesh reinforcement, and shotcrete.

9. A reinforcement method for wide-site leveling and filling of slopes containing weak interlayers as described in claim 1, characterized in that: In step S4, after the anchor spraying support is completed, deep drainage holes (7) are set on the slope of the second leveling (6B), and the deep drainage holes (7) extend to the first leveling (6A).

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