Soft and hard interbedding rock mass slope grouting reinforcement method under dry-wet cycle condition

Abstract

The invention discloses a grouting reinforcement method for a soft and hard interbed rock mass slope under the dry-wet cycle condition. The grouting reinforcement method comprises the following steps that a soft and hard interbed rock mass numerical model is constructed, and parameter calibration is conducted on the model; uniaxial compression test numerical simulation is carried out on the soft and hard interbedded rock mass models under different working conditions; the stability of the soft and hard interbedded rock mass is evaluated, and rock mass damage risks and weak links in different areas are determined; and grouting reinforcement is carried out according to the obtained result. According to the method, multiple groups of variables are set, the influence of each factor on the overall strength of the rock mass is comprehensively researched, and the rock mass stability is comprehensively and accurately evaluated; the drilling direction and distance are adjusted according to the rock stratum dip angle, it is ensured that grout effectively permeates into key parts, and the reinforcing effect is improved; accurate regulation and control of grouting parameters are achieved, and it is ensured that grout fully fills cracks and does not disturb a rock mass structure; and grouting parameters are adjusted according to the deviation and the change rate, and the grouting reinforcement effect is ensured.

Description

Technical Field

[0001] The present invention relates to a grouting reinforcement method, and in particular to a more accurate grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions. Background Art

[0002] Existing technologies have many defects in the stability assessment and grouting reinforcement of soft and hard interbedded rock slopes under dry-wet cycle conditions. In the stability assessment process, most of them only consider the effect of a single or a few factors on the stability of the rock mass, and are unable to fully analyze the complex situation under the coupling of multiple factors such as rock layer inclination, soft or hard rock strength degradation, and dry-wet cycles, resulting in inaccurate assessment results. In the design of grouting reinforcement, a general approach is often adopted, which does not closely combine the unique failure mode and crack evolution law of soft and hard interbedded rock mass, making it difficult to achieve efficient reinforcement. There is a lack of precise control means for the setting of grouting process parameters, which can easily damage the rock structure due to excessive pressure, or insufficient pressure can prevent the slurry from fully diffusing, affecting the reinforcement effect. In addition, there is a general lack of real-time monitoring and dynamic adjustment mechanisms during the grouting process. When problems such as sudden pressure drop and abnormal grouting volume occur, they cannot be detected in time and effective countermeasures cannot be taken, and ultimately it is difficult to ensure the overall effectiveness of grouting reinforcement. Summary of the Invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a more accurate grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions.

[0004] Technical solution: The grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions of the present invention comprises the following steps:

[0005] (1) Construct a numerical model of soft and hard interbedded rock mass and calibrate the model parameters;

[0006] (2) Numerical simulation of uniaxial compression tests on soft-hard interbedded rock models under different working conditions;

[0007] (3) Assess the stability of interbedded soft and hard rock masses and identify the rock failure risks and weak links in different areas;

[0008] (4) Implement grouting reinforcement according to the results of step (1), step (2) and step (3).

[0009] Furthermore, the step (1) of constructing the numerical model of the soft and hard interbedded rock mass includes selecting simulation software and a model connection method, the simulation software adopts PFC2d software, and the model connection method adopts parallel bonding model connection.

[0010] Furthermore, the step (2) includes dividing the stress-strain curve into an elastic deformation stage, a stable crack expansion stage, an unstable crack expansion stage, and a post-peak stage; and defining a multi-peak phenomenon, a pre-peak multi-peak phenomenon, and a post-peak multi-peak phenomenon based on multiple stress drop phenomena occurring during the change of the stress-strain curve.

[0011] Furthermore, the step (3) includes:

[0012] (3.1) Degradation control area: Define the uniaxial compressive strength degradation rate d of the rock mass after the soft rock and hard rock strength degrade by 50%. Based on the relationship d2-d1, the degrading area is divided into the soft rock main control area, the hard rock main control area, the soft and hard rock independent control areas, and the soft and hard rock common control area.

[0013] (3.2) The relationship between the number of microcracks and strain of the specimens under various working conditions is presented; the strain corresponding to the slow growth stage of specimens with different inclination angles β is different. The slow growth stage of specimens with β = 0°-45° corresponds to a larger strain, the slow growth stage of specimens with β = 60° is shorter, and the slow growth stage of specimens with β = 75°-90° is accompanied by fluctuations in the growth rate of the number of microcracks.

[0014] Furthermore, the step (3.1) divides the failure results of the soft and hard interbedded rock mass into five categories, namely TM through-layer failure, CS soft layer crushing, hard layer through-layer failure, SD inter-layer shear failure, TD rock layer splitting failure, and HD sliding shear failure along the bedding plane.

[0015] Furthermore, the change in the number of microcracks in step (3.2) with strain is divided into five stages: no microcracks are generated in the linear elastic stage of segment OA; new cracks begin to generate in segment AB and develop steadily; microcracks are generated at a lower rate in segment BC; microcracks develop rapidly in segment CD, and the macroscopic damage of the sample is significant; the internal structure of the sample in segment DE is destroyed, and it is finally completely destroyed to form a macroscopic fracture surface.

[0016] Furthermore, the penetration and filling process of the slurry in the rock mass in step (4) is described by establishing the following penetration model:

[0017]

[0018] Where V is the permeable volume of the slurry in time t, k is the permeability coefficient of the rock mass, A is the cross-sectional area of ​​the grouting borehole, ΔP is the grouting pressure difference, μ is the dynamic viscosity of the slurry, and L is the permeation path length of the slurry in the rock mass.

[0019] Furthermore, in step (4), for high-angle rock mass, the drilling direction is adjusted according to the layer inclination angle β, and the drilling angle is determined by the trigonometric function relationship θ=90°-β, where θ is the angle between the drill hole and the vertical direction, and the drill hole spacing S is determined according to the rock mass integrity coefficient I and the degree of fracture development F.

[0020]

[0021] Among them, r is the diffusion radius of slurry in rock mass, which is related to grouting pressure and material.

[0022] Furthermore, the grouting pressure control in step (4) includes, for the soft rock part, based on the soft rock compressive strength σ s , set the upper limit of grouting pressure P s-max =0.6σ s ; For hard rock parts, increase the grouting pressure;

[0023] By formula P h =P0+k1C, where P0 is the initial grouting pressure and k1 is a coefficient related to rock mass properties. This promotes the diffusion of slurry in hard rock fissures. The grouting pressure is optimized through field tests and monitored in real time using pressure sensors.

[0024] The grouting volume should be considered comprehensively considering the rock porosity n, the degree of crack development F and the volume of the reinforcement range V r Through calculation, the grouting volume Q of each borehole is calculated by the formula Q=V r ×(n+F) for preliminary estimation, and then make corrections based on the actual grouting pressure changes and slurry flow conditions in combination with field tests.

[0025] Furthermore, in step (4), when the actual grouting pressure P deviates from the theoretical design pressure P0 by more than ±10%, or the flow rate Q f If the change exceeds ±15% within t = 5 minutes, stop grouting immediately; use the pressure sensor and flow sensor to monitor the data in real time, and calculate the pressure deviation according to the formula ΔP = P-P0:

[0026]

[0027] Where ΔQ f is the flow rate change rate, Q f0 The initial flow rate is set, and the grouting parameters are adjusted according to the deviation and change rate. The pressure adjustment amount ΔP adj =k p ΔP,k p is the pressure adjustment coefficient, and the value of the flow adjustment ΔQ fadj =k q ΔQ f k q is the flow adjustment coefficient.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0029] (1) The present invention uses PFC2d software to construct a numerical model, simulates discontinuous media based on the discrete element method, and accurately describes the behavior of soft and hard interlayered rock masses. By setting multiple groups of variables, the influence of various factors on the overall strength of the rock mass is comprehensively studied, achieving a comprehensive and accurate assessment of the stability of the rock mass.

[0030] (2) Based on the results of numerical simulation and stability assessment, the present invention designs grouting schemes for different failure modes and microcrack evolution stages. According to the characteristics of soft rock and hard rock, slurries with good fluidity and fast early strength growth and slurries with strong adhesion are selected respectively. The drilling direction and spacing are adjusted according to the inclination of the rock formation to ensure that the slurry effectively penetrates into the key parts and improve the reinforcement effect.

[0031] (3) The present invention establishes a slurry permeability model to quantify the slurry permeability and provide theoretical support for parameter determination. Through formulas and algorithms, the upper limit of grouting pressure is set according to the compressive strength of soft rock, and the grouting pressure is adjusted considering the complexity of internal cracks in hard rock, thereby achieving precise control of grouting parameters and ensuring that the slurry fully fills the cracks without disturbing the rock structure.

[0032] (4) During the grouting process, the present invention utilizes pressure sensors and flow sensors to monitor the grouting volume and grouting pressure changes in real time, and adjusts the grouting parameters according to the deviation and change rate to ensure the grouting reinforcement effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The stability assessment flow chart for soft and hard interbedded rock masses;

[0034] Figure 2 Flow chart for grouting quantity estimation and correction;

[0035] Figure 3 Schematic diagram of grouting drilling arrangement. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0037] The grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions of the present invention comprises the following steps:

[0038] Step 1: Build the foundation of the numerical model

[0039] Simulation software and model connection method were selected: PFC2d software was used due to its advantages in simulating discontinuous media (such as interbedded soft and hard rock) based on the discrete element method. A model of interbedded soft and hard rock with a size of 100 mm × 50 mm and a soft / hard rock particle size ratio of 1.66 was constructed, with particles connected by a parallel bond model.

[0040] Determining model parameters: Using the interbedded soft and hard surrounding rock of a hydropower station's diversion chamber as samples, on-site sampling and laboratory uniaxial compression testing were conducted. After multiple experiments, samples with peak strengths of 21.15 MPa and 82.66 MPa were selected to represent undegraded soft rock and hard rock, respectively. The model parameters were calibrated to achieve peak strengths of 20 MPa for soft rock and 80 MPa for hard rock. Based on research findings, the model's microscopic parameters were adjusted to match the strength standards after degradation, and the same interlayer parameters were uniformly used. The specific particle microscopic parameters and model microscopic parameters are shown in Tables 1 and 2:

[0041] Table 1 Particle microscopic parameters

[0042]

[0043] Table 2 Parameters used in the rock numerical model

[0044]

[0045] In step 1:

[0046] Input: It is known that the PFC2d software has advantages in simulating discontinuous media (such as soft and hard interbedded rock) based on the discrete element method, which is the basis for selecting this software.

[0047] The relevant information of the soft and hard interbedded surrounding rocks of the diversion chamber of a hydropower station was used as the object sample of the study.

[0048] The soft and hard interlayered surrounding rock was sampled on site, and the test data was obtained from uniaxial compression tests in the laboratory (the samples with peak strengths of 21.15 MPa and 82.66 MPa obtained from multiple experiments represent undegraded soft rock and hard rock, respectively).

[0049] Relevant research results are used as a reference to adjust the model's microscopic parameters to meet the strength standards after degradation.

[0050] Output: The PFC2d software was used for simulation. A soft-hard interbedded rock model with a size of 100 mm × 50 mm and a soft / hard rock particle size ratio of 1.66 was constructed. The particles were connected by a parallel bonding model, thus completing the construction of the numerical model.

[0051] The model parameters were calibrated so that the peak strength of soft rock was 20 MPa and that of hard rock was 80 MPa. The same interlayer parameters were uniformly adopted to obtain the specific particle microscopic parameters and model microscopic parameter table.

[0052] Step 2: Design a simulation plan

[0053] To investigate the effects of stratum dip angle β and soft / hard rock strength degradation on the overall strength of the interbedded rock mass, multiple variables were set. The dip angle ranged from 0° to 15°, with a total of seven values. The strength degradation coefficient K was defined, where K represents the undegraded specimen, K1 represents degraded hard rock, and K2 represents degraded soft rock. Specifically, four variables were designed: K1 = 0.25, K1 = 0.5, K2 = 0.25, and K2 = 0.5.

[0054] Numerical simulations of uniaxial compression tests were conducted on models of interbedded soft and hard rock under different working conditions to provide an in-depth analysis of the stress-strain characteristics. The stress-strain curve was divided into the elastic deformation stage, the stable crack growth stage, the unstable crack growth stage, and the post-peak stage. Furthermore, based on the multiple stress drops that occur during the stress-strain curve, precise definitions were given for the multi-peak phenomenon, the pre-peak multi-peak phenomenon, and the post-peak multi-peak phenomenon.

[0055] In step 2:

[0056] Input: The rock mass model constructed in step 1 is 100 mm × 50 mm in size, with a soft / hard rock particle size ratio of 1.66 and interlayered soft and hard layers connected by a parallel bond model. The model parameters are calibrated to have a peak strength of 20 MPa for soft rock and 80 MPa for hard rock.

[0057] The purpose of this study was to investigate the effects of stratum inclination and soft / hard rock strength degradation on the overall strength of interbedded rock masses. The inclination angle was set to 0° and incremented by 15°, with seven values ​​set. The strength degradation coefficient K was defined (K represents the undegraded specimen, K1 represents degraded hard rock, and K2 represents degraded soft rock). The four sets of variables, K1 = 0.25, K1 = 0.5, K2 = 0.25, and K2 = 0.5, were determined.

[0058] Output: Data obtained from numerical simulation of uniaxial compression tests on a soft-hard interbedded rock mass model under different working conditions (composed of different layer inclinations and soft / hard rock strength degradation coefficients).

[0059] After an in-depth analysis of the stress-strain characteristics, the results were divided into the elastic deformation stage, the stable crack expansion stage, the unstable crack expansion stage, and the post-peak stage.

[0060] Precisely defined multimodality, pre-peak multimodality, and post-peak multimodality.

[0061] Step 3: Assess rock mass stability

[0062] Peak Strength Analysis: Numerical simulation results, as shown in Table 3, show that the peak strength of the interbedded soft and hard rock mass exhibits a U-shaped trend, initially decreasing and then increasing, with increasing inclination angle, consistent with relevant strength theory. The minimum peak strength of the specimens under all conditions occurs mostly at 45° or 60°. Degradation of the soft / hard rock strength significantly influences the peak strength of the rock mass, with hard rock strength degradation having the greatest impact on specimens at a 90° inclination angle and soft rock strength degradation having the greatest impact on specimens at a 45° inclination angle.

[0063] Table 3 Peak strength change rate of soft / hard rock after degradation

[0064]

[0065] Divide the degradation control area: define the uniaxial compression strength degradation rate d of the rock mass after the soft rock / hard rock strength deteriorates by 50%, and divide it into the soft rock main control area, hard rock main control area, soft / hard rock separate control area and soft and hard rock common control area according to the relationship d2-d1.

[0066] For example, when β = 0°, it is the common control area; when β is within a specific range, it is the soft rock main control area; when β = 60°, it is the soft rock independent control area; when β = 75°, it is the soft rock main control area; when β = 90°, it is the hard rock main control area. The formula for calculating the strength degradation rate d is:

[0067]

[0068] The failure results of soft and hard interbedded rock masses are divided into five categories, as shown in Table 4, namely TM (trans-layer tensile failure), CS (soft layer crushing and hard layer trans-layer tensile failure), SD (along-layer shear failure), TD (stratum splitting tensile failure), and HD (sliding shear failure along bedding plane).

[0069] Table 4 Failure modes and specific classifications of soft and hard interbedded rock masses

[0070]

[0071] The inclination angle of the rock formation has a significant influence on the failure morphology. TM-type through-layer tensile failure mainly occurs in low-inclination specimens; when β = 45°, it is mainly SD rock formation shear failure; when β = 60°, it is mainly HD rock formation sliding shear failure along the bedding plane; when β = 90°, it is TD rock formation splitting tensile failure. Rock mass degradation also affects the failure morphology. At different inclination angles, the degradation of hard or soft rock will cause changes in the crack distribution and the degree of specimen failure.

[0072] The relationship between the number of microcracks and strain in the specimens under various operating conditions exhibited slow growth and rapid growth phases. The corresponding strains during the slow growth phase varied for specimens with different inclination angles. The slow growth phase for specimens with β = 0°-45° corresponded to larger strains, while the slow growth phase for specimens with β = 60° was shorter. The slow growth phase for specimens with β = 75°-90° was accompanied by fluctuations in the rate of microcrack growth. The number of cracks first decreased and then increased with increasing inclination angle. Cracks in the hard rock control zone and the common control zone were more prone to propagation and formation, resulting in more significant macroscopic damage.

[0073] The number of microcracks changes with strain and is divided into five stages: no microcracks are generated in the linear elastic stage of the OA segment; new cracks begin to appear in the AB segment and develop steadily; microcracks are generated at a low rate in the BC segment; microcracks develop rapidly in the CD segment, and the macroscopic damage of the specimen is significant; the internal structure of the specimen in the DE segment is destroyed, and finally completely destroyed to form a macroscopic fracture surface. Rock mass degradation and rock layer inclination have different effects on the evolution of microcracks. For example, under different inclination angles, the degradation of hard rock affects the formation and expansion of cracks, and the degradation of soft rock affects the bearing capacity and failure mode of the specimen. Figure 1 shown.

[0074] In step 3:

[0075] Input: Uniaxial compression test data of the soft-hard interbedded rock model under different working conditions obtained through numerical simulation in step 2, including stress-strain curve data and related multi-peak phenomenon analysis results.

[0076] Define the relevant concepts of the uniaxial compression strength degradation rate of rock mass after the soft rock / hard rock strength deteriorates by 50% and the standards for dividing different control areas.

[0077] A knowledge system for classifying rock failure forms, such as the standard for classifying the failure results of soft and hard interlayered rock into five categories: TM, CS, SD, TD, and HD.

[0078] Output: Conclusion on the trend of the peak strength of the soft and hard interbedded rock mass with the inclination angle, that is, the overall U-shaped trend of first decreasing and then increasing, the angles at which the minimum peak strength of the specimens under various working conditions often appears, and the influence of the strength degradation of soft / hard rock on the peak strength of specimens at different inclination angles.

[0079] The specific regional division results of soft rock main control area, hard rock main control area, soft / hard rock separate control area and soft and hard rock common control area are divided according to the strength degradation rate.

[0080] Classification results of the failure morphology of interbedded soft and hard rock masses, as well as specific conclusions on the effects of rock layer inclination and rock mass degradation on failure morphology, including typical failure modes at different inclination angles and how degradation affects crack distribution and specimen damage degree.

[0081] The stage characteristics of the relationship between the number of microcracks and strain of the specimens under various working conditions, such as the characteristics of the slow growth and rapid growth stages, as well as the strain differences corresponding to the slow growth stage of specimens with different inclination angles, and the changing trend of the number of cracks with inclination angle.

[0082] Detailed classification results of the five stages of microcrack number change with strain, as well as specific analysis conclusions on the different effects of rock mass deterioration and rock layer inclination on the evolution of microcracks, such as the impact of hard rock deterioration on crack formation and expansion at different inclination angles, and the impact of soft rock deterioration on the bearing capacity and failure mode of the specimen.

[0083] Step 4: Implement grouting reinforcement

[0084] Grouting reinforcement is a key step to improve the stability of soft and hard interbedded rock slopes and should be carried out in close accordance with the results of the first three steps, such as Figure 2 shown.

[0085] The five stages of microcrack number variation with strain, as well as the impact of rock mass degradation and rock formation inclination on microcrack evolution, are closely related to the implementation of grouting reinforcement. In terms of grouting timing, the stable development of new cracks in the AB segment is a good time to grout. Timely grouting at this time can effectively prevent the cracks from transitioning to the rapid development stage in the CD segment, significantly improving the reinforcement effect. In terms of grouting material selection, soft rock degradation affects the specimen's bearing capacity and failure mode. Its microcracks develop rapidly, requiring materials with good fluidity and the ability to quickly solidify and increase strength, such as specific cement-based slurries. Hard rock degradation affects crack formation and expansion, requiring highly adhesive slurries, such as chemical and cement-based mixed slurries, to match the microcrack evolution characteristics of different rock masses. In the design of grouting technology, the crack propagation mode caused by hard rock deterioration is different at different inclination angles. At low inclination angles, drilling vertically to the surface is conducive to penetrating and filling hard rock cracks. At high inclination angles, the drilling direction needs to be adjusted according to the surface inclination to ensure that the slurry penetrates into the cracks of the hard rock surface. The grouting pressure control also needs to be based on the bearing capacity of the soft rock at different microcrack development stages and the complex cracks caused by deterioration of the hard rock. For example, the grouting pressure of the soft rock in the BC section should be reasonably controlled, while the pressure of the hard rock can be appropriately increased according to the formula to promote slurry diffusion.

[0086] Based on the numerical model constructed in Step 1 and the simulation scheme designed in Step 2, the mechanical behavior and failure modes of the rock mass were clarified under different rock layer inclination angles β and soft / hard rock strength degradation conditions. For example, at low inclination angles, the rock mass may primarily exhibit a through-bedding failure (TM) mode, while at high inclination angles, a sliding shear failure (HD) mode along the bedding plane may occur. These results provide important guidance for grouting reinforcement.

[0087] The penetration and filling process of slurry in the rock mass is described by establishing the following penetration model:

[0088]

[0089] Among them, V is the penetration volume of the slurry within time t, k is the permeability coefficient of the rock mass (related to the integrity of the rock mass and the degree of fracture development. The better the integrity and the fewer the fractures, the smaller the value of k), A is the cross-sectional area of the grouting borehole (determined by the borehole diameter and affecting the initial diffusion area of the slurry), ΔP is the grouting pressure difference (the driving force for the slurry flow and directly related to the grouting pressure), μ is the dynamic viscosity of the slurry (for different grouting materials such as cement-based and chemical slurries, the value of μ varies significantly and affects the fluidity of the slurry), and L is the penetration path length of the slurry in the rock mass (related to the borehole depth and the rock mass structure). The above formula quantifies the penetration of the slurry under different rock mass conditions and grouting parameters, providing a theoretical basis for reasonably selecting grouting materials and determining grouting process parameters to ensure that the slurry can efficiently fill the key parts and enhance the integrity and strength of the rock mass. <0000​​​​​​​​​​​​​​​​​​​​​=P0+k1C (P0 is the initial grouting pressure, k1 is a coefficient related to rock mass properties), which promotes the diffusion of grouting fluid within hard rock fissures. Grouting pressure is optimized through field testing and monitored in real time using pressure sensors to ensure that the grouting fluid fully fills the fissures without disturbing the rock mass structure.

[0094] The grouting volume should be considered comprehensively considering the rock porosity n, the degree of crack development F and the volume of the reinforcement range V r Through calculation, the grouting volume Q of each borehole is calculated by the formula Q=V r ×(n+F) for preliminary estimation, then combined with field tests, make corrections based on actual grouting pressure changes and slurry flow conditions to ensure that the grouting volume meets filling requirements without causing waste. During the grouting process, pressure sensors and flow sensors are used to monitor the grouting volume and grouting pressure changes in real time. If a sudden drop in pressure or an abnormal increase in grouting volume occurs, grouting is immediately stopped, the cause analyzed, and grouting parameters such as pressure and flow are adjusted. Treatment measures such as sealing leaks are also taken to ensure the grouting reinforcement effect and enhance slope stability.

[0095] When the actual grouting pressure p deviates from the theoretical design pressure P0 by more than ±10%, or the flow rate Q f If the change exceeds ±15% within t = 5 minutes, stop grouting immediately; use the pressure sensor and flow sensor to monitor the data in real time, and calculate the pressure deviation according to the formula ΔP = P-P0:

[0096]

[0097] Where ΔQ f is the flow rate change rate, Q f0 The initial flow rate is set, and the grouting parameters are adjusted according to the deviation and change rate. The pressure adjustment amount ΔP adj =k p ΔP,k p is the pressure adjustment coefficient, and the value of the flow adjustment ΔQ fadj =k q ΔQ f k q It is the flow adjustment coefficient, which is used to ensure the grouting reinforcement effect and enhance the stability of the slope.

[0098] The rock mass stability assessment in step 3 identifies rock mass failure risks and weak links in different areas. For example, at certain inclination angles and deterioration conditions, the rock mass has low peak strength and active crack evolution, requiring more intensive grouting reinforcement. Therefore, when implementing grouting reinforcement, based on these assessment results, targeted adjustments to grouting parameters are made, such as increasing drilling density, increasing grouting pressure, or using more suitable grouting materials, to maximize the reinforcement effect.

[0099] The present invention focuses on the stability assessment and grouting reinforcement of soft and hard interbedded rock slopes under dry-wet cycle conditions. By using PFC2d software to construct a numerical model with a size of 100mm×50mm, a soft / hard rock particle size ratio of 1.66, and particles connected by a parallel bonding model, parameter calibration was performed based on on-site sampling and test data of the soft and hard interbedded surrounding rock of a hydropower station water diversion chamber. Multiple sets of variables were set, covering 7 layer inclinations and 4 sets of strength degradation coefficients, and uniaxial compression test numerical simulations were carried out on the rock model under different working conditions. The rock stability was evaluated from multiple dimensions such as peak strength, failure morphology, and microcrack evolution. Based on the evaluation results, suitable grouting materials were selected for different rock properties and microcrack stages, and the grouting process was scientifically designed, including adjusting the drilling direction and spacing according to the rock layer inclination, accurately calculating and controlling the grouting pressure and grouting volume through formulas, and using sensors for real-time monitoring. The grouting parameters were dynamically adjusted according to the pressure deviation and flow rate change rate to achieve accurate assessment of the stability of the soft and hard interbedded rock slope and efficient reinforcement.

Claims

1. A grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions, characterized in that: The steps include: (1) Construct a numerical model of soft and hard interbedded rock mass and calibrate the model parameters; (2) Numerical simulation of uniaxial compression tests on soft-hard interbedded rock models under different working conditions; (3) Assess the stability of interbedded soft and hard rock masses and identify the rock failure risks and weak links in different areas; (4) Implement grouting reinforcement according to the results of step (1), step (2) and step (3).

2. The grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions according to claim 1, characterized in that: The step (1) of constructing a numerical model of a soft-hard interbedded rock mass includes selecting simulation software and a model connection method. The simulation software adopts PFC2d software, and the model connection method adopts parallel bonding model connection.

3. The grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions according to claim 1, characterized in that: The step (2) includes dividing the stress-strain curve into an elastic deformation stage, a stable crack expansion stage, an unstable crack expansion stage, and a post-peak stage; and defining a multi-peak phenomenon, a pre-peak multi-peak phenomenon, and a post-peak multi-peak phenomenon based on multiple stress drop phenomena occurring during the stress-strain curve change process.

4. The grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions according to claim 1, characterized in that: The step (3) comprises: (3.1) Degradation control area: Define the uniaxial compressive strength degradation rate d of the rock mass after the soft rock and hard rock strength degrade by 50%. Based on the relationship d2-d1, the degrading area is divided into the soft rock main control area, the hard rock main control area, the soft and hard rock independent control areas, and the soft and hard rock common control area. (3.2) The relationship between the number of microcracks and strain of the specimens under various working conditions is presented; the strain corresponding to the slow growth stage of specimens with different inclination angles β is different. The slow growth stage of specimens with β = 0°-45° corresponds to a larger strain, the slow growth stage of specimens with β = 60° is shorter, and the slow growth stage of specimens with β = 75°-90° is accompanied by fluctuations in the growth rate of the number of microcracks.

5. The grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions according to claim 4, characterized in that: The step (3.1) divides the failure results of the soft and hard interbedded rock mass into five categories, namely TM through-layer failure, CS soft layer crushing, hard layer through-layer failure, SD inter-layer shear failure, TD rock layer splitting failure, and HD sliding shear failure along the bedding plane.

6. The method for reinforcing a slope of a soft and hard interbedded rock mass under dry-wet cycle conditions according to claim 4, characterized in that: The number of microcracks in step (3.2) changes with strain and is divided into five stages: no microcracks are generated in the linear elastic stage of segment OA; new cracks begin to generate in segment AB and develop steadily; microcracks are generated at a lower rate in segment BC; microcracks develop rapidly in segment CD, and the macroscopic damage of the sample is significant; the internal structure of the sample in segment DE is destroyed, and it is finally completely destroyed to form a macroscopic fracture surface.

7. The method for reinforcing a slope of soft and hard interbedded rock mass under dry-wet cycle conditions according to claim 1, characterized in that: The penetration and filling process of the slurry in the rock mass in step (4) is described by establishing the following penetration model: Where V is the permeable volume of the slurry in time t, k is the permeability coefficient of the rock mass, A is the cross-sectional area of ​​the grouting borehole, ΔP is the grouting pressure difference, μ is the dynamic viscosity of the slurry, and L is the permeation path length of the slurry in the rock mass.

8. The method for reinforcing a slope of soft and hard interbedded rock mass under dry-wet cycle conditions according to claim 1, characterized in that: In step (4), for high-angle rock mass, the drilling direction is adjusted according to the layer inclination angle β, and the drilling angle is determined by the trigonometric function relationship θ=90°-β, where θ is the angle between the drill hole and the vertical direction. The drilling spacing S is determined according to the rock mass integrity coefficient I and the degree of fracture development F. Among them, r is the diffusion radius of slurry in rock mass, which is related to grouting pressure and material.

9. The method for reinforcing a slope of a soft and hard interbedded rock mass under dry-wet cycle conditions according to claim 1, characterized in that: The grouting pressure control in step (4) includes, for the soft rock portion, based on the soft rock compressive strength σ s , set the upper limit of grouting pressure P s-max =0.6σ s ; For hard rock parts, increase the grouting pressure; By formula P h =P0+k1C, where P0 is the initial grouting pressure and k1 is a coefficient related to rock mass properties. This promotes the diffusion of slurry in hard rock fissures. The grouting pressure is optimized through field tests and monitored in real time using pressure sensors. The grouting volume should be considered comprehensively considering the rock porosity n, the degree of crack development F and the volume of the reinforcement range V r Through calculation, the grouting volume Q of each borehole is calculated by the formula Q=V r ×(n+F) for preliminary estimation, and then make corrections based on the actual grouting pressure changes and slurry flow conditions in combination with field tests.

10. The grouting reinforcement method for soft and hard interbedded rock slopes under dry-wet cycle conditions according to claim 1, characterized in that: In the step (4), when the actual grouting pressure P deviates from the theoretical design pressure P0 by more than ±10%, or the flow rate Q f If the change exceeds ±15% within t = 5 minutes, stop grouting immediately; use the pressure sensor and flow sensor to monitor the data in real time, and calculate the pressure deviation according to the formula ΔP = P-P0: Where ΔQ f is the flow rate change rate, Q f0 The initial flow rate is set, and the grouting parameters are adjusted according to the deviation and change rate. The pressure adjustment amount ΔP adj =k p ΔP,k p is the pressure adjustment coefficient, and the value of the flow adjustment ΔQ fadj =k q ΔQ f k q is the flow adjustment coefficient.

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