A low-disturbance strip-shaped root pile-grouting rock mass-anchor cable reinforcing system for a rock mass slope and a construction method thereof

Abstract

The application discloses a kind of broken rock mass side slope low disturbance strip root pile-grouting rock mass-anchor cable reinforcement system and its construction method, the reinforcement system includes root pile group, grouting rock mass and prestressed anchor cable, the root pile group is sequentially penetrated by upper and lower strong deformation zone of broken rock mass, weak deformation zone and then stretches into stable rock mass, the grouting rock mass is located on strong deformation zone, the prestressed anchor cable is sequentially penetrated by upper and lower grouting rock mass, strong deformation zone and weak deformation zone and then stretches into stable rock mass.The reinforcement system of the application only needs to drill root pile group in certain elevation strip of side slope downward, without large-scale excavation support, can prevent side slope instability caused by construction disturbance to the greatest extent.Form one or more long and thick root pile and grouting rock mass strip on broken rock mass side slope by root pile group and grouting between piles, the strip is good in integrity, can bear greater anchoring force, and anchoring effect is stronger.

Description

Technical Field

[0001] This invention belongs to the field of slope treatment technology, and in particular relates to a low-disturbance strip root pile-grouting rock mass-anchor cable reinforcement system for fractured rock slopes and its construction method. Background Technology

[0002] In slope stabilization engineering, commonly used reinforcement measures include slope cutting and load reduction, slope stabilization, anchoring, retaining walls, frame slope protection, grouting reinforcement, and combinations of various measures. Slope cutting and load reduction is a technique that improves slope stability by reducing the slope gradient or the load at the rear edge of the slope; it is often used to manage push-type landslides. Slope stabilization involves adding a weight load at the leading edge of the landslide to counteract the sliding motion; it is often used when the slope at the leading edge of the landslide is relatively gentle. Anchor bolts and soil nailing are both shallow reinforcement methods, often used for slopes with fractured soil or weak strata. Prestressed anchor cables are a deep reinforcement method, suitable for slopes that are high and where the potential fracture surface is deep. Retaining walls are a commonly used support measure, often used in combination with other measures, and are suitable for slopes with relatively good construction conditions but limited area and a relatively gentle slope. Framed slope protection features structural stability, convenient construction, strong adaptability, and environmental friendliness. It is laid on the slope surface and is often combined with anchoring measures to achieve overall slope stability. Grouting reinforcement is commonly used for slopes with fractured rock and well-developed joints and fissures. Under pressure, the grout penetrates through the joints and fissures around the borehole wall, cementing the fractured slope soil and rock to form a unified structure.

[0003] In the construction of hydropower stations and other engineering projects, the geological conditions of engineering slopes are becoming increasingly complex. The stabilization and management of ultra-high slopes with high unloading has become a highly challenging issue, and conventional management measures are often insufficient to meet engineering requirements. In ultra-high unloading slopes, the surface layer often contains fractured rock masses, characterized by their large area, deep thickness, steep slope, high elevation, and fragmented structure. The slopes are often in a critical stability state, and even slight disturbances during construction can easily induce slope instability, endangering the safety of the project.

[0004] Commonly used reinforcement measures for stabilizing fractured rock masses under extreme unloading conditions present the following problems: The fractured rock slopes are characterized by high elevations and steepness, making slope reduction, embankment construction, and frame-reinforced slope protection extremely difficult; the slope fractures are deep, limiting the effectiveness of conventional anchoring methods such as anchor bolts and soil nails, which only work on the shallow surface and cannot address the overall stability of the fractured rock mass; the anchoring ends of prestressed anchor cables are located in the fractured zone, making tensioning and locking difficult; the fractured area is large, the terrain is steep and easily disturbed, and retaining walls and other support measures have limited effectiveness and are difficult to form a stable working face; frame-reinforced slope protection covers a wide area and is difficult to implement. Therefore, a reinforcement system capable of solving these problems is needed.

[0005] Patent document CN115404886A discloses a construction method for a prefabricated micropile-anchor cable combined support structure. This support structure consists of a precast top slab, micropiles, and prestressed anchor cables, and is mainly used for rapid emergency treatment of landslides. However, because the precast top slab is placed on the slope surface and covers a relatively small area, when the slope is steep and the rock mass is fractured, the stiffness of the surface rock mass is only slightly improved, failing to fully utilize and leverage the inherent strength of the rock mass. Furthermore, the micropiles experience only a single stress direction, and the anchoring effect of the prestressed anchor cables is limited. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a low-disturbance strip root pile-grouting rock mass-anchor cable reinforcement system for fractured rock slopes and its construction method.

[0007] The present invention is achieved through the following technical solutions.

[0008] This invention provides a low-disturbance strip-root pile-grouting rock mass-anchor cable reinforcement system for fractured rock slopes, comprising a root pile group, grouting rock mass, and prestressed anchor cables. The root pile group penetrates the strong deformation zone and the weak deformation zone of the fractured rock mass sequentially from top to bottom, and then extends into the stable rock mass below the fractured rock mass. The prestressed anchor cables penetrate the grouting rock mass, the strong deformation zone, and the weak deformation zone sequentially from top to bottom, and then extend into the stable rock mass below the fractured rock mass. The grouting rock mass is located on the strong deformation zone.

[0009] Preferably, the root pile group includes vertical root piles and inclined root piles, and grouting pipes are provided on the outer walls of the vertical root piles and inclined root piles, with the grouting pipes extending into the strong deformation zone.

[0010] Preferably, the vertical and slanted tree root piles are arranged in alternating rows.

[0011] Preferably, the root pile group is made of one or more of the following materials: cast-in-place piles, steel pipe piles, and steel pipe anchor piles.

[0012] Preferably, the prestressed anchor cable includes an outer anchor block, which is set on the grouting rock mass.

[0013] A construction method for a low-disturbance strip root pile-grouting rock mass-anchor cable reinforcement system for fractured rock slopes includes the following steps: S1: First, drill pile holes. After the pile holes are formed, solidify the wall and install grouting pipes. Then, pour in concrete or inject cement mortar to form piles, creating a group of tree root piles. S2: Grouting is carried out between piles in the strong deformation zone. The grouting is performed through the grouting pipes reserved during pile construction to form grouting rock mass in the strong deformation zone. S3: Prestressed anchor cable construction: Once the root pile group and grouting rock mass have reached the design age, the cable holes for prestressed anchor cable construction can be drilled. The cable holes avoid the piles of the root pile group and pass through the grouting rock mass between the piles before entering the stable rock mass. The external anchor of the prestressed anchor cable is located on the grouting rock mass. After the prestressed anchor cable construction is completed, the reinforcement system construction is finished.

[0014] Preferably, in step S1, the pile holes are drilled in a staggered manner, and the method of using casing drilling is determined based on the rock mass fracture condition during pile hole drilling.

[0015] Preferably, in step S2, grouting is performed using pressure grouting. During grouting, the holes located on the outside of the root pile group are grouted first, and then the holes located on the inside of the root pile group are grouted.

[0016] Preferably, the grouting method in step S2 is two-stage or three-stage grouting, and grouting should be performed after the pile is completed.

[0017] Preferably, the grout used in step S2 can be one or more of cement mortar, cement paste, and fluid fine aggregate concrete. In step S2, normal grout is first used for grouting, and then grout with a concentration 1.1-3 times that of normal grout is used for finishing.

[0018] The beneficial effects of this invention are as follows: 1. This invention minimizes slope disturbance. This reinforcement system only requires drilling root pile groups downward within a few elevation zones of the slope, without the need for large-scale excavation and support, thus maximizing the prevention of slope instability caused by construction disturbance.

[0019] 2. This invention offers better overall integrity, stronger anchoring effect, and higher safety. Through root pile groups and inter-pile grouting, one or more long and thick strips composed of root piles and grouted rock mass are formed on the fractured rock slope. These strips have good integrity, can withstand greater anchoring forces, and provide stronger anchoring.

[0020] 3. This invention allows for flexible arrangement. Based on the slope stability calculation and analysis results, and combined with the geological conditions of the fractured rock mass, the slope reinforcement work can be completed by adjusting the number of rows of vertical and inclined root piles, the grouting range, and the design anchoring force of the prestressed anchor cables, and by flexibly selecting one or more levels of reinforcement structure strips according to the construction conditions.

[0021] 4. The present invention is convenient and quick to construct. Implementing support measures on steep, fractured rock slopes is generally difficult. The reinforcement system of this invention is laid out at the same elevation, without excavation of the slope. The construction technology of drilling root piles and grouting reinforcement is mature. The formed root pile-grouting rock mass structure provides a working platform for the installation of prestressed anchor cables, reducing construction difficulty and making construction more convenient and quick. Attached Figure Description

[0022] Figure 1 This is a three-dimensional axonometric schematic diagram of the present invention; Figure 2 This invention relates to a root pile, grouting rock mass structure, and construction cross-section diagram; Figure 3 This is a schematic diagram of the planar structure of the present invention; In the figure: 1-Strong deformation zone, 2-Weak deformation zone, 3-Tree root pile group, 31-Vertical tree root pile, 32-Inclined tree root pile, 4-Grouting rock mass, 5-Anchor cable outer anchor, 6-Prestressed anchor cable tensioning section, 7-Prestressed anchor cable anchoring section, 8-Stable rock mass, 9-Slope excavation outline, 10-Grouting guide pipe. Detailed Implementation

[0023] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0024] Example: like Figures 1 to 3 As shown, a low-disturbance strip-root pile-grouting rock mass-anchor cable reinforcement system for fractured rock slopes includes a root pile group 3, a grouting rock mass 4, and prestressed anchor cables. The root pile group 3 penetrates the strong deformation zone 1 and the weak deformation zone 2 of the fractured rock mass from top to bottom and then extends into the stable rock mass 8. The prestressed anchor cables penetrate the grouting rock mass 4, the strong deformation zone 1, and the weak deformation zone 2 from top to bottom and then extend into the stable rock mass 8. The grouting rock mass 4 is located on the strong deformation zone 1.

[0025] The fractured rock mass is divided into a strong deformation zone 1 and a weak deformation zone 2. The strong deformation zone 1 is the area of ​​intense deformation on the surface of the fractured rock mass, and the lower layer is the weak deformation zone 2. The two are mainly divided according to the degree of fracture and deformation of the rock mass.

[0026] The root pile group 3 includes vertical root piles 31 and inclined root piles 32. Grouting pipes 10 are provided on the outer walls of the vertical root piles 31 and inclined root piles 32. The grouting pipes 10 extend into the strong deformation zone 1. The vertical root piles 31 and inclined root piles 32 make the root pile group 3 not subjected to a single force direction, and thus have good stability.

[0027] The vertical tree root piles 31 and the inclined tree root piles 32 are arranged in a staggered row. The spacing between the anchor cables and the design anchoring force are determined based on the slope stability analysis calculation results, with a preferred spacing of 0.5-1m.

[0028] The root pile group 3 is made of one or more of the following materials: cast-in-place piles, steel pipe piles, and steel pipe anchor piles.

[0029] The prestressed anchor cable includes an outer anchor block 5, a tensioning section 6, and an anchoring section 7. The outer anchor block 5 is set on the grouting rock mass 4. The prestressed anchor cable passes through the grouting rock mass 4, the strong deformation zone 1, and the weak deformation zone 2 from top to bottom and then extends into the stable rock mass 8. The anchoring section 7 extends into the stable rock mass 8.

[0030] A construction method for a low-disturbance strip root pile-grouting rock mass-anchor cable reinforcement system for fractured rock slopes includes the following steps: S1: First, drill pile holes. After the pile holes are formed, solidify the wall and install grouting pipe 10. Then, pour in concrete or inject cement mortar with a strength grade of not less than M30 to form a tree root pile group 3. S2: Grouting is carried out between piles in the strong deformation zone 1. The grouting is carried out through the grouting pipe 10 reserved during pile formation. The grout combines with the material in the strong deformation zone 1 to form grouting rock mass 4 in the strong deformation zone 1. S3: Prestressed anchor cable construction: Once the root pile group 3 and the grouting rock mass 4 have reached the designed stable age, the drilling of the cable holes for the prestressed anchor cable construction can begin. The cable hole drilling location is in the lower part of the slope of the grouting rock mass 4. The cable hole avoids the piles of the root pile group 3 and passes through the grouting rock mass 4 between the piles before entering the stable rock mass 8. The prestressed anchor cable anchoring section 7 is drilled to a stratum with better geological conditions. After the drilling is completed, the prestressed anchor cable construction is carried out. The external anchor of the prestressed anchor cable is set on the grouting rock mass 4. After the prestressed anchor cable construction is completed, the construction of the reinforcement system is completed.

[0031] In step S1, the spacing between drilled pile holes is 0.5m-1m. The pile holes are drilled in a staggered manner. The choice between using casing drilling depends on the rock mass's fracture condition. Casing drilling involves simultaneously drilling and inserting the casing, or inserting the casing ahead of the drill bit and then drilling along with it, until the hole penetrates to a depth of at least 3m into the lower stable rock mass 8. After hole formation, the hole wall is stabilized. This method prevents hole wall collapse during drilling.

[0032] In step S2, grouting is performed using pressure injection. The grouting pressure is selected according to the degree of rock mass fracturing and the size of the borehole spacing, and can be 0.2MPa~0.5MPa. During grouting, the holes located on the outside of the root pile group 3 are grouted first, and then the holes located on the inside of the root pile group 3 are grouted.

[0033] In step S2, the grouting method between holes is either two-stage or three-stage grouting, and grouting is performed after the pile is completed.

[0034] The post-grouting is a method of grouting after the vertical root piles 31 and the inclined root piles 32 are formed, through grouting pipes 10 pre-embedded in the pile holes.

[0035] The two-sequence grouting method is as follows: the grouting guide holes 10 on each row of vertical tree root piles 31 or inclined tree root piles 32 are divided into two sequences, namely the first sequence hole and the second sequence hole. When grouting, the first sequence hole is grouted first and then the second sequence hole is grouted.

[0036] The three-sequence grouting method is as follows: the grouting guide holes 10 on each row of vertical tree root piles 31 or inclined tree root piles 32 are divided into three sequences, namely, sequence one hole, sequence two hole and sequence three hole. When grouting, the sequence one hole is grouted first, then the sequence two hole is grouted, and finally the sequence three hole is grouted.

[0037] The grout used in step S2 can be one or more of cement mortar, cement paste, and fluid fine aggregate concrete. In step S2, normal grout is first used for grouting, and then grout with a concentration 1.1-3 times that of normal grout is used for finishing.

[0038] Before the construction of the reinforcement system, one or more levels of reinforcement system are set up according to the actual situation of the slope. The reinforcement system is constructed sequentially from high elevation to low elevation. The elevation of the first or more levels is determined according to the slope stability analysis calculation results. The reinforcement system is set above the slope excavation outline 9.

[0039] The anchoring force of the prestressed anchor cable design is determined based on the slope stability analysis calculation results.

[0040] In this invention, the root pile group 3 itself has a certain reinforcement effect, mainly through the anchoring effect of prestressed anchor cables to reinforce the slope. The anchoring force of the anchor cables is transmitted and diffused to the slope through the strip-shaped vertical root piles 31, the inclined root piles 32, and the grouting rock mass 4. Then, through the joint action of the multi-level reinforcement system strips, a multi-level root pile group-grouting rock mass-anchor cable reinforcement system is constructed, ultimately achieving the stability and safety of the slope.

[0041] This invention has been successfully applied to a fractured rock slope in a hydropower project. Three rows of steel pipe root piles were installed within the root pile-grouting rock mass-anchor cable reinforcement strip, with an average depth of approximately 20m, a row spacing of 0.8m, and a hole diameter of 200mm. M30 cement mortar was used for rock mass grouting at a pressure of 0.5MPa. Core sampling after construction showed good bonding within the strip, with the reinforced solids exhibiting a saturated compressive strength exceeding the design value of 25MPa. After the root piles and grouting rock mass met the strength requirements, prestressed anchor cables with a spacing of 5m and an anchoring force of 1000kN were installed on the strip. The stability of the treated fractured rock slope met the design requirements; after 12 months of monitoring and verification, the prestressed anchor cables functioned normally, the slope showed no abnormal deformation, and the treated fractured rock slope demonstrated good stability.

Claims

1. A low-disturbance strip-shaped root pile-grouting rock mass-anchor cable reinforcement system for breaking up rock mass slopes, characterized in that: The structure includes a group of tree root piles (3), a grouting rock mass (4), and prestressed anchor cables. The group of tree root piles (3) passes through the strong deformation zone (1) and weak deformation zone (2) of the fractured rock mass from top to bottom and then extends into the lower stable rock mass (8). The prestressed anchor cables pass through the grouting rock mass (4), the strong deformation zone (1), and the weak deformation zone (2) from top to bottom and then extend into the lower stable rock mass (8). The grouting rock mass (4) is located on the strong deformation zone (1). The root pile group (3) includes vertical root piles (31) and inclined root piles (32). The outer walls of the vertical root piles (31) and inclined root piles (32) are provided with grouting pipes (10), which extend into the strong deformation zone (1). The vertical tree root piles (31) and the slanted tree root piles (32) are arranged in a staggered pattern in front and behind rows; The prestressed anchor cable includes a prestressed anchor cable outer anchor block (5), which is set on the grouting rock mass (4).

2. The low-disturbance strip-shaped root pile-grouting rock mass-anchor cable reinforcement system for breaking rock mass slope according to claim 1, characterized in that: The root pile group (3) is made of one or more of the following materials: cast-in-place piles, steel pipe piles, and steel pipe anchor piles.

3. The construction method of the low-disturbance strip-shaped root pile-grouting rock mass-anchor cable reinforcement system for the fractured rock mass slope according to any one of claims 1-2, characterized in that, Includes the following steps: S1: First, drill pile holes. After the pile holes are formed, solidify the wall and set up grouting pipes (10). Then, pour in concrete or inject cement mortar to form piles and form a tree root pile group (3). S2: Grouting is carried out between the piles in the strong deformation zone (1). The grouting is carried out through the grouting pipe (10) reserved during pile formation, and grouting rock mass (4) is formed in the strong deformation zone (1). S3: Prestressed anchor construction: When the root pile group (3) and the grouting rock mass (4) reach the design age, the cable holes for prestressed anchor construction can be drilled. The cable holes avoid the piles of the root pile group (3) and pass through the grouting rock mass (4) between the piles before entering the stable rock mass (8). After the drilling is completed, the prestressed anchor construction is carried out. The external anchor of the prestressed anchor is set on the grouting rock mass (4). After the prestressed anchor construction is completed, the construction of the reinforcement system is completed.

4. The construction method of the low-disturbance strip-shaped root pile-grouting rock mass-anchor cable reinforcement system for breaking rock mass slope according to claim 3, characterized in that: In step S1, the pile holes are drilled in a staggered manner. The method of drilling with casing is determined based on the rock mass fracture condition.

5. The construction method of the low-disturbance strip-shaped root pile-grouting rock mass-anchor cable reinforcement system for the rock mass slope according to claim 3, characterized in that: In step S2, grouting is performed by pressure injection. During grouting, the holes located outside the root pile group (3) are grouted first, and then the holes located inside the root pile group (3) are grouted.

6. The construction method of the low-disturbance strip-shaped root pile-grouting rock mass-anchor cable reinforcement system for the rock mass slope according to claim 3, characterized in that: In step S2, the grouting method between holes is either two-stage or three-stage grouting, and the grouting time is after the pile is completed.

7. The construction method of the low-disturbance strip root pile-grouting rock mass-anchor cable reinforcement system for fractured rock slopes as described in claim 3, characterized in that: The grout used in step S2 can be one or more of cement mortar, cement paste, and fluid fine aggregate concrete. During grouting, normal grout is first used for injection, and then grout with a concentration 1.1-3 times that of normal grout is used for finishing.

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