Red-bed soft rock long and large bedding slope supporting structure and supporting design method

Abstract

The application belongs to the technical field of geotechnical engineering slope support, and specifically discloses a red-bed soft rock long and large bedding slope supporting structure and a supporting design method, which comprises the following steps: S1, geological model establishment; S2, determination of a sliding surface and a first deformation length; S3, calculation of a sliding thrust; S4, sliding thrust judgment; S5, comprehensive support of the bedding slope by double-row anti-slide piles and prestressed anchor cables, wherein the anchoring section needs to be embedded into a stable stratum; S6, setting of a drainage system, including multilayer drainage holes and slope surface interception and drainage; and S7, slope surface protection. The application can avoid insufficient or excessive design of the supporting range.

Description

Technical Field

[0001] This invention relates to the field of slope protection technology in geotechnical engineering, specifically to a slope protection structure and design method for long bedding slopes in red soft rock. Background Technology

[0002] Red bed soft rock is a type of rock mass with special engineering geological properties. It is mainly composed of mudstone, siltstone, etc., and contains a large number of hydrophilic minerals. It is characterized by easy softening, easy weathering, and low strength. When this type of rock mass forms a long bedding slope, the weak interlayers or weak surfaces between layers are very likely to form controlling slip surfaces under the action of excavation unloading and water, leading to slope instability.

[0003] The failure mode of long bedding slopes in red bed soft rock after excavation is mainly characterized by the creeping and sliding of the slope or incline rock mass along the weak argillaceous layer towards the free face. As the displacement increases, the rock mass undergoes sliding deformation, and the sliding mass is torn apart at the rear of the deformation zone. Before slope failure, the rock and soil mass within the slope undergoes stress redistribution due to the influence of the free face. Initially, the normal stress and shear stress in the weak argillaceous layer within a certain range at the front increase significantly. The shear strength in the weak argillaceous layer gradually transitions from peak shear strength to residual strength from the free face to the rear, while the resistance to sliding at the weak argillaceous layer gradually decreases. When the resistance to sliding is less than the sliding force, the rock and soil mass in this section undergoes overall sliding failure along the weak argillaceous layer. At the same time, a new free face is created at the rear of the sliding mass. Affected by this free face, the stress in the slope rock and soil mass undergoes stress redistribution again, repeating the deformation and failure process of the rock and soil mass in the previous section. This process continues until the rock mass gradually collapses until the resistance to sliding at the weak argillaceous layer is equivalent to the sliding force of the rock mass, reaching a stable state. Therefore, as long as the stability of the soil and rock mass in the first section of the bedding slope or the slope is controlled and the stress redistribution area of ​​the soil and rock mass is limited to a finite range, the stability of the bedding slope can be guaranteed.

[0004] Existing support methods have the following limitations:

[0005] (1) The time-dependent strength of the rock mass is not considered: the strength of the soft rock in the red bed decays significantly over time. Traditional methods do not take this characteristic into account, which leads to an unsafe design.

[0006] (2) Water sensitivity was not specifically considered: conventional drainage measures may not be sufficient to cope with the characteristic of red bed soft rock being strongly softened when exposed to water.

[0007] (3) Large deviation in thrust calculation: The parameters of red bed soft rock are easy to change, and the traditional thrust calculation method has a large error.

[0008] (4) Limited measures: It is difficult to cope with the characteristics of large deformation and gradual damage of red bed soft rock slopes.

[0009] Therefore, there is an urgent need for a comprehensive design method that integrates precise analysis, multiple protections, and long-term stability, specifically targeting the characteristics of red bed soft rock. Summary of the Invention

[0010] This invention provides a design method for the support of long bedding slopes in red soft rock, with the aim of avoiding insufficient or excessive support.

[0011] This invention is achieved through the following technical solution: a design method for slope support of long bedding-parallel red soft rock, comprising the following steps:

[0012] S1. Geological model establishment;

[0013] S2. Determine the slip surface and initial deformation length: Determine the critical instability length using a combination of numerical analysis, theoretical calculation, and empirical judgment. ;

[0014] S3. Calculate the sliding thrust: Considering the strength attenuation characteristics of red bed soft rock, the improved transfer coefficient method is used to calculate the sliding thrust.

[0015] S4. Determine the sliding thrust. If the sliding thrust is greater than 2500 kN / m, some potential sliding bodies need to be removed along the layer to reduce the thrust. If the sliding thrust is less than or equal to 2500 kN / m, support should be applied directly.

[0016] S5. Double-row anti-slide piles and prestressed anchor cables are used to provide comprehensive support for the bedding slope.

[0017] S6. Install a drainage system, including multi-layer drainage holes and slope surface interception drainage;

[0018] S7. Slope protection.

[0019] Compared with existing technologies, this solution has the following advantages and beneficial effects:

[0020] In this scheme, the geological model is established through step S1, and step S2 adopts a coupled method of numerical analysis, theoretical calculation and empirical judgment, taking into account the effects of strain softening of red bed soft rock and groundwater seepage. Compared with the single method, this scheme effectively improves the calculation accuracy, ensures that the determination of the critical instability range is more in line with reality, and avoids insufficient support range or over-design.

[0021] Step S3 uses an improved transfer coefficient method to quantify the reduction in shear strength caused by long-term weathering and softening of red bed soft rock by water. It more accurately reflects the stress changes of the slope throughout its entire life cycle than traditional methods, avoiding insufficient support due to failure to consider the aging effect.

[0022] This scheme, through S4-S7, addresses the characteristics of red bed soft rock and the huge sliding thrust. It adopts comprehensive measures such as bedding clearance and load reduction, double-row anti-slide piles, prestressed anchor cables, drainage system and slope protection, which can enhance anti-slide and protection capabilities and ensure the long-term stability of the support.

[0023] Furthermore, based on detailed engineering geological surveys, S1 clarified the strata occurrence, weathering characteristics, distribution of weak interlayers, groundwater occurrence and seepage paths, and weak interlayers of the red bed soft rock bedding slope. , Parameters, establish corresponding geological models, This refers to the cohesion of the weak interlayer under saturation. It represents the internal friction angle of the weak interlayer under saturated conditions.

[0024] Beneficial effects: Through detailed investigation, the occurrence (strike, dip angle, dip direction) and weathering characteristics (strong / medium / slight weathering zones) of rock strata are clarified, as well as the distribution (thickness, continuity, spatial distribution) and groundwater occurrence (water level depth, seepage path, water-rich areas). This allows for the precise capture of the core characteristics of red bed soft rock: well-developed bedding, weak interlayers controlling sliding, and high water sensitivity.

[0025] Compared to the limitations of traditional exploration methods that emphasize surface over depth and overall structure over interlayers, this method can avoid deviations in support design caused by overlooking local weak interlayers or hidden groundwater channels.

[0026] Based on the excavation height H, the most unfavorable weak interlayer was identified as the potential sliding surface. The key structural surfaces controlling slope instability were specifically targeted: the instability of red bed bedding slopes is mostly controlled by gently dipping weak interlayers (especially mudstone interlayers that are easily softened by water). By comparing the burial depth, dip angle, and relationship with the excavation slope angle of different interlayers, the interlayer that is most easily penetrated after excavation and has the lowest shear strength was selected as the potential sliding surface. This avoids misjudging non-controlling rock layer interfaces as sliding surfaces, and provides a clear target for subsequent calculation of critical instability length and analysis of sliding thrust.

[0027] Furthermore, the numerical analysis in S2 establishes a fluid-structure interaction model that considers the strain softening characteristics of red bed soft rock and the effect of groundwater seepage. The strength reduction method is used to calculate the slope safety factor and predict the failure range, thus determining the numerical solution. ;

[0028] The theoretical calculations are based on the limit equilibrium theory and the theoretical solution for calculating the softening characteristics of red bed soft rock upon contact with water. ;

[0029] The empirical judgment is based on engineering experience in red bed soft rock to determine the empirical length of the first segment of the bedding-parallel sliding body. Ultimately , , The maximum value of the three is used as the critical instability length in the design. .

[0030] Beneficial effects: The fluid-structure interaction model in this scheme incorporates the strain softening characteristics of red bed soft rock (i.e., the strength decreases with deformation after stress) and the effect of groundwater seepage. The strength reduction method is used to simulate the entire process of slope stability to instability, quantifying the potential failure range at different water levels and deformation stages. The obtained numerical solution... It can reflect the dynamic effects of heterogeneity and water-rock interaction in soft rock. Based on the limit equilibrium theory, the softening characteristics of red bed soft rock upon contact with water are specifically introduced (using parameters). , The theoretical solution is derived. The theoretical calculation results better match the instability characteristics of bedding slopes in red beds. (Empirical judgment) Based on engineering practice in red-bed soft rock (such as the correlation between the slip length of the first segment of a bedding landslide and the thickness of the landslide body), this approach overcomes the limitations of numerical analysis and theoretical calculations under complex geological conditions (such as local interlayer discontinuities and fracture development); ultimately, it adopts... , , The maximum value is used as This achieves a triple guarantee of rigorous theoretical calculations, dynamic numerical simulations, and risk assessment based on engineering experience.

[0031] Step S2, through multi-method coupling, leverages the numerical model's ability to simulate complex processes and the mechanical rigor of theoretical formulas, while also mitigating the risks associated with theoretical simplification by utilizing engineering experience, ultimately determining the critical instability length. It can accurately adapt to the core characteristics of red bed soft rock, such as strain softening, water softening, and bedding sliding, providing a scientific and safe basis for the design of subsequent support structures (such as the location of anti-slide piles and the range of clearing and load reduction).

[0032] Furthermore, the numerical analysis in S2 establishes a fluid-structure interaction model that considers the strain softening characteristics of red bed soft rock and the effect of groundwater seepage. Typical cross-sections are selected, and the strength reduction method is used to calculate the safety factor of the slope under natural and saturated conditions, thus determining the numerical solution. ;

[0033] The theoretical calculation formula is:

[0034] ;

[0035] In the formula: The cohesion (kPa) of the weak interlayer under saturation. The internal friction angle (°) of the weak interlayer under saturated conditions. The unit weight (kN / m³) of the saturated sliding mass rock and soil. The slope excavation height is in meters (m). The dip angle is (°). The slope angle is (°).

[0036] Empirical judgment is based on determining the empirical length as 5 to 10 times the thickness of the bedding plane. , , When <15m, take 15m≤ Linear interpolation is used when the length is <30m. 30m≤ Take 10 at a time .

[0037] Beneficial effects: The fluid-structure interaction model in this scheme specifically incorporates the strain softening characteristics of red bed soft rock (strength decays with cumulative deformation) and the effect of groundwater seepage. By comparing and analyzing the slope safety factor under natural (dry) and saturated (water-covered) conditions using the strength reduction method, the weakening effect of water on the strength of soft rock can be quantified, and the potential instability range under different conditions can be directly predicted (numerical solution). ).

[0038] Theoretical Formula Directly using mechanical parameters under saturation conditions ( , , Specifically, the critical instability length of red bed soft rock after softening upon contact with water is quantified: (Formula omitted) The item directly reflects the dip angle of the weak interlayer. With shear strength Matching relationship (when) near When the denominator decreases, The increase is significant, consistent with the pattern that gently dipping interlayers on red-bed bedding slopes are more prone to instability. The item is related to the slope excavation height. With slope angle This calculation demonstrates the amplification effect of excavation on the instability range. Compared to general theoretical formulas (which do not distinguish between natural and saturated states), this calculation accurately reflects the most unfavorable conditions after rainfall or groundwater soaking, providing a theoretical basis for water-sensitivity adaptation in support design and avoiding problems caused by using natural state parameters. Too small.

[0039] experience length Based on 5 to 10 times the thickness of the bedding plane ( This is determined directly from a large number of engineering case studies on red bed soft rock slopes—the initial sliding length of a red bed bedding landslide is often equal to the thickness of the sliding mass (approximate to the excavation height). The correlation is positive, and this empirical value can effectively cover the calculation bias caused by theoretical simplification (such as ignoring local cracks and interlayer discontinuities) and the limitations of numerical model boundary conditions. The final value is... (Numerical solution) (Theoretical solution) The maximum value of the (empirical length) is taken as the critical instability length. This creates a triple guarantee: the dynamism of numerical simulation, the mechanical rigor of theoretical calculations, and the risk-averse nature of engineering experience, ensuring... It can cover the maximum possible instability range of red bed soft rock under the most unfavorable working conditions (saturation state, full development of strain softening, and triggering of local defects).

[0040] Furthermore, the improved transfer coefficient method introduces an intensity attenuation coefficient. , Over time change, , As the decay rate constant, the corrected formula for calculating glide thrust is:

[0041] ;

[0042] in, ;

[0043] Let be the remaining sliding thrust (kN / m) at the end of the i-th block. The thrust (kN / m) transmitted from the (i-1)th block. Let be the thrust transfer coefficient from block i-1 to block i. For safety reasons, Let be the weight of the i-th block (kN / m). Let be the inclination angle (°) of the bottom sliding surface of the i-th block. Let be the cohesion (kPa) of the i-th block surface in a saturated state. Let be the internal friction angle (°) of the i-th block surface when it is in a saturated state. Let be the length (m) of the bottom sliding surface of the i-th block.

[0044] Beneficial effects: The shear strength (cohesion) of red bed soft rock (especially weak interlayers) subjected to long-term weathering and groundwater soaking decreases. internal friction angle The strength decays gradually over time, and the traditional transfer coefficient method, which uses a fixed strength parameter, cannot reflect this characteristic. However, the improved method uses a strength decay coefficient... ( The decay rate constant is (For time) changes dynamically over time: initial stage ( (smaller) Approaching 1, anti-slip force term ( The thrust is relatively large, resulting in a downward thrust. Smaller; over time ( (increase) Decrease, and the anti-slip force term decreases. The corresponding increase precisely matches the actual evolution law of the red bed soft rock strength decreasing over time → the sliding thrust gradually increasing.

[0045] The parameters of the anti-slip force term in the formula ( , All values ​​are taken under saturation conditions, combined with... The attenuation effect is considered in two ways: the softening effect of water on soft rock and the long-term attenuation effect of its strength. Red bed soft rock already has lower strength in its saturated state than in its natural state; the added effect of time attenuation further weakens its anti-sliding ability. Therefore, the calculation of sliding thrust is more consistent with the most unfavorable conditions such as torrential rain and long-term groundwater action. Sliding thrust The dynamic calculation results directly guide intelligent control measures such as staged pressure adjustment of prestressed anchor cables and stress monitoring of anti-slide piles. For example, based on the calculations, it can be seen that after 6 months... A 10% increase allows for the development of a plan to adjust the anchor cable prestress from 80% to 100% of the design value in advance; if calculations show a certain block If growth is too rapid, targeted measures can be taken to strengthen drainage in the area or add anchor cables in certain areas to avoid blind regulation.

[0046] Furthermore, regarding S4 and the judgment of sliding thrust, if the sliding thrust is >2500kN / m, it is necessary to remove some potential sliding bodies along the layer to reduce the thrust. If the sliding thrust is ≤2500kN / m, it can be directly supported. After removing some potential sliding bodies along the layer, the sliding thrust should be ≤2500kN / m. When clearing along the layer, a platform of 2m to 5m should be set every 40m to 60m.

[0047] S5. Double-row anti-slide piles, including a front row and a rear row of anti-slide piles. Both the front and rear rows of anti-slide piles are made of bored cast-in-place piles with a diameter of 2.0m to 2.5m or square piles with a cross-section of 2×3m. The front row of anti-slide piles should be close to the toe of the slope, and the distance between the rear row of anti-slide piles and the front row of anti-slide piles should be 50m to 80m. A connecting beam is set at the top of the front row of anti-slide piles to form an integral load-bearing structure, and 2 to 3 rows of anchor cables are set starting 1.5m below the top of the piles, with a spacing of 1.5m. The anchoring section of the anchor cables must be located in stable bedrock.

[0048] The prestressed anchor cables are tension type, with the anchorage section embedded in stable bedrock to a depth of 6m~10m. They are equipped with a prestress adjustment device to adjust the prestress value in stages according to the strength decay curve of the red bed soft rock. The initial prestress is 80% of the design value, adjusted to 100% after 6 months, and further increased to 110% after 12 months.

[0049] S6. The drainage hole in the drainage system penetrates the potential slip surface to a depth of 1m to 2m. The drainage system also includes an intelligent monitoring module and an emergency drainage pump. The intelligent monitoring module can collect groundwater level and drainage flow data in real time. When the water level rises by more than 50cm / d, the emergency drainage pump is automatically started.

[0050] S7. Slope protection: After clearing the slope, first spray modified concrete containing Bacillus pasteurization solution onto the slope, then insert anchor bolts several days later, and finally spray vegetated concrete to form a composite protective layer of microbial mineralization reinforcement, anchor bolt anchoring, and ecological restoration.

[0051] Beneficial effects: This scheme specifically reduces the sliding force generated by the self-weight of the landslide body, avoiding the destruction of the original balance of the slope by excessive excavation. During layer-by-layer clearing, a 2m-5m platform should be installed every 40m-60m. This platform not only distributes some of the slope pressure but also provides operational space for the drainage system and slope protection, while mitigating rainwater erosion of the slope. Compared to a design without platforms, this reduces soil and water loss on the slope.

[0052] In this scheme, large-diameter bored piles of 2.0m to 2.5m or square piles with a cross section of 2×3m are arranged in double rows to form a double line of defense. The front row of anti-slide piles directly blocks the shallow sliding body, while the rear row of anti-slide piles bears the deep thrust. The double row of anti-slide piles can improve the support stiffness and effectively suppress the gradual expansion of the bedding sliding.

[0053] The pile top connecting beam connects the two rows of piles into a whole, avoiding local damage caused by uneven stress on individual piles, thereby improving the overall deformation resistance.

[0054] In this design, the anchorage section of the tension-type anchor cable is embedded 6-10m into stable rock strata to ensure reliable transmission of anchoring force. Phased prestress adjustment (initial 80% → 100% after 6 months → 110% after 12 months) precisely matches the strength decay pattern of the red bed soft rock: the initial low prestress avoids plastic deformation of the soft rock due to excessive instantaneous stress, and the force is gradually increased as the strength decreases, always maintaining sufficient active anti-sliding force, reducing the risk of anchor cable failure compared to a fixed prestress design.

[0055] In this scheme, drainage holes penetrate 1m to 2m into the potential slip surface, directly draining the enriched water near the slip surface (the core trigger for bedding-parallel landslides in red beds), thus weakening the softening effect of water on soft rock at its source. The intelligent monitoring module is linked with the emergency drainage pump, automatically initiating pumping when the water level rises by more than 50cm / d (such as after a rainstorm), preventing a sharp decline in the strength of soft rock caused by a sudden rise in water level.

[0056] Modified concrete containing Bacillus pasteurellium solution enhances the compressive strength of the surface soft rock through microbial mineralization (generating calcium carbonate cement), effectively inhibiting surface weathering and spalling. Subsequent installation of anchor bolts and spraying of vegetation concrete form a three-layer protection system of microbial reinforcement, mechanical anchoring, and vegetation slope stabilization, effectively improving the overall erosion resistance of the slope.

[0057] Vegetated concrete is suitable for the arid and barren environment of red bed areas. It has a high survival rate of vegetation, which not only achieves ecological restoration, but also further enhances the integrity of the slope through the root network. Compared with traditional sprayed anchor protection, it can reduce the risk of surface collapse.

[0058] Furthermore, the critical instability length in S2 Employing a spatiotemporal dual-dimensional computational model:

[0059] Spatially, considering the differences in the degree of soft rock weathering and seepage intensity in the slope crest, middle, and toe regions, the numerical solution is used. Theoretical solution Length of experience Assign dynamic weights based on region;

[0060] In the time dimension, a time coefficient is introduced in conjunction with the slip surface evolution prediction results. , The critical buckling length increases with the rate of slip surface expansion. The corrected formula for calculating the critical buckling length is: , The time is calculated from the completion of slope excavation or the completion of the support system, and the unit is days.

[0061] Beneficial effects: The weathering degree (strong / medium / slight weathering) and seepage intensity (water-rich area / water-poor area) of different areas (slope top, slope middle, and slope toe) of red bed soft rock slopes vary significantly. The slope toe is subjected to the dual effects of groundwater soaking and slope pressure, resulting in the most severe weathering of soft rock, the most concentrated seepage, and the highest risk of instability. The slope top, on the other hand, may experience shallow sliding due to surface water infiltration.

[0062] By region , , Assign dynamic weights (e.g., increase seepage sensitivity in the slope toe area) Weighting, increasing empirical values ​​in the hilltop region The weighting upgrades the calculation of critical instability length from a uniform value across the entire domain to a regionally differentiated value, avoiding the underestimation of local high-risk areas by the traditional single weight.

[0063] The soft rock surface of the red bed will slide over time ( Due to intensified weathering and the long-term effects of groundwater, it has gradually expanded, transforming the traditional static... The calculation cannot reserve a safety margin for future expansion, which can easily lead to initial safety but later instability.

[0064] Introducing a time coefficient that increases with the slip surface spreading rate Through formula , making L d Dynamic growth over time: the faster the slip surface expands ( The larger ( The higher the magnification, the more it covers the potential range of future instability.

[0065] The spatial dimension focuses on the current risk differences in different regions, while the temporal dimension focuses on the future evolution trend of overall risk. The coupling of the two makes... It can accurately match the actual instability risks in various areas of the slope at present, and also proactively reserve safety redundancy for long-term evolution, forming a dual guarantee of spatial precision and temporal advancement.

[0066] Furthermore, the calculation of the sliding thrust in S3 incorporates a multi-field coupling correction term involving seepage, deformation, and aging. The corrected calculation formula is as follows:

[0067] ;

[0068] in, This is a correction term for the additional force caused by seepage. Real-time pore water pressure; This is a correction term for the surface evolution. The coefficient of the slip surface spread rate. The time is calculated from the completion of slope excavation or the completion of the support system, and the unit is days.

[0069] Beneficial effects: One of the core causes of the softening of red bed soft rock upon contact with water is the pore water pressure generated by groundwater seepage. This pressure counteracts the effective normal stress on the sliding surface, reducing shear strength, and directly generates additional sliding force. Traditional calculations do not quantify this effect separately, easily underestimating the peak thrust under water action.

[0070] ( (The specific gravity of water) is used to dynamically calculate the additional thrust of seepage on the i-th block using real-time pore water pressure data: during rainfall or groundwater enrichment, Increase Synchronous increase, downward thrust This improvement allows for a more accurate reflection of the driving effect of water-rock interaction on instability. The slip surface of red bed soft rock will change over time (…). Due to weathering, creep, and water erosion, it gradually expands (the rate of expansion is from...). (Quantification) The increase in the length of the slip surface directly leads to an expansion of the slip force distribution range and an enhanced thrust accumulation effect. Traditional calculations are based only on the initial slip surface state and cannot reflect this long-term evolution process.

[0071] Through the slip surface expansion rate coefficient With time The coupling of the quantified slip surface extension contributes additionally to the thrust of the i-th block: the slip surface extension becomes more significant over time. , The larger ( The larger, The closer it gets to the actual thrust under long-term instability conditions.

[0072] Instability of red bed soft rock slopes is due to strength decay over time. (manifestation), groundwater seepage ( (Implication), dynamic extension of the sliding surface ( This reflects the result of the synergistic effect of multiple factors: strength attenuation weakens the anti-slip force, seepage and slip surface expansion exacerbate the sliding force, and the three factors together determine the dynamic changes in thrust.

[0073] The revised formula fully incorporates the multi-field effects of anti-sliding force attenuation and sliding force enhancement. Compared with the traditional calculation that only considers strength attenuation, the thrust results are more consistent with the actual instability process of red bed soft rock, and the calculation error is reduced.

[0074] Real-time pore water pressure ( ), slip surface spread rate coefficient ( This can be obtained through the intelligent monitoring module, allowing the glide thrust to be measured. It can be updated in real time and directly guide the coordinated control of multiple support measures: when When seepage intensifies, the corresponding area's drainage system should be activated first to strengthen water control, while the anchor cable prestress should be slightly increased to offset the additional thrust; when When the growth is too rapid (the slip surface expands faster), adjust the monitoring frequency of the anti-slip piles, and if necessary, add auxiliary anti-slip structures in the direction of slip surface expansion.

[0075] Compared with traditional fixed-cycle regulation, this model enables on-demand regulation and precise reinforcement, effectively improving the response efficiency of the support system and avoiding resource waste or regulatory lag caused by blind adjustments.

[0076] A support structure for long bedding slopes in red bed soft rock includes:

[0077] Layered clearing and load reduction unit: consists of multi-stage cut slopes and platforms;

[0078] Double-row anti-slide pile unit: includes front row anti-slide piles, rear row anti-slide piles and connecting beams. There are multiple front row anti-slide piles and multiple rear row anti-slide piles. The two ends of the connecting beam are respectively connected to two adjacent front row anti-slide piles. Prestressed anchor cables are installed on the front row anti-slide piles.

[0079] Prestressed anchor cable unit: It consists of a tension anchor cable, a prestressing adjustment device and an anchoring section. The anchoring section is embedded in stable bedrock, and one end of the anchor cable is connected to the prestressing adjustment device.

[0080] Drainage unit: includes multiple drainage holes and slope interception drainage structure. The drainage holes penetrate the potential slip surface. The drainage holes are equipped with permeable pipes and reverse filter layers. The reverse filter layer is located between the permeable pipes and the drainage holes. The slope interception drainage structure is a water interception ditch. The water interception ditch is set at the bottom of the slope of each level of the slope.

[0081] Slope protection unit: consists of a modified concrete layer containing bacterial solution, anchor bolts, and a vegetation concrete layer.

[0082] Beneficial effects: The red-bed soft rock long bedding slope support structure in this scheme addresses the technical challenges of high water sensitivity, easy strength decay, high risk of bedding sliding, and easy corrosion of red-bed soft rock through the coordinated operation of five major units: bedding clearing and load reduction, double-row anti-slide piles, prestressed anchor cables, drainage, and slope protection. Furthermore, the permeable pipe and filter layer design in this scheme prevents drainage hole blockage.

[0083] Furthermore, the filter layer includes an inner layer and an outer layer. The inner layer is geotextile, and the outer layer is quartz sand or gravel. The inner layer wraps around the outside of the permeable pipe, and the outer layer fills the space between the inner layer and the wall of the drainage hole.

[0084] Beneficial effects: Geotextile can accurately intercept fine particles in red bed soft rock, preventing them from entering the permeable pipe with the water flow and clogging the permeable pores of the pipe wall. The outer layer filled with quartz sand or gravel forms a coarse filter layer. The outer layer is filled between the permeable pipe and the hole wall, which can support the soft rock of the drainage hole wall, reduce the weathering and peeling of the hole wall, and prevent the loss of soft rock particles due to water seepage (avoiding the collapse of the rock mass around the hole). Attached Figure Description

[0085] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0086] Figure 1 This is a flowchart illustrating an embodiment of the design method for supporting long bedding slopes in red-bed soft rock according to the present invention;

[0087] Figure 2 This is a three-dimensional geological model diagram of a long bedding slope in an embodiment of the design method for supporting long bedding slopes in red soft rock according to the present invention;

[0088] Figure 3 This is an example diagram of a geological profile model of a long bedding slope in a red bed soft rock slope support structure according to the present invention.

[0089] Figure 4 This is a schematic diagram of the retaining structure of a long bedding slope in red soft rock according to an embodiment of the present invention;

[0090] Figure 5 for Figure 4 A magnified view of a section at point A in the middle;

[0091] Figure 6 This is a schematic diagram of the connection between the connecting beam and the front row of anti-slide piles in an embodiment of a red-bed soft rock long bedding slope support structure of the present invention;

[0092] Figure 7 This is a schematic diagram of the drainage hole structure in an embodiment of a long bedding slope support structure for red soft rock according to the present invention.

[0093] The attached diagram shows the markings and corresponding component names:

[0094] 1. Slope body, 2. Platform, 3. Interception ditch, 4. Front row of anti-slide piles, 5. Rear row of anti-slide piles, 6. Anchor cable, 7. Drainage hole, 700. Water pipe, 710. Inner layer, 720. Outer layer, 8. Connecting beam. Detailed Implementation

[0095] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0096] As one embodiment of this application, such as Figure 1 , Figure 2 and Figure 3 As shown in the figure, this embodiment provides a design method for the support of long bedding slopes in red soft rock, including the following steps:

[0097] S1. Geological Model Establishment: Based on detailed engineering geological surveys, the geological model is established to determine the strata occurrence, weathering characteristics, distribution of weak interlayers, groundwater occurrence and seepage paths, and weak interlayers of the red bed soft rock bedding slope. , Parameters, establish corresponding geological models, This refers to the cohesion of the weak interlayer under saturation. The internal friction angle of the weak interlayer under saturation;

[0098] S2. Determine the slip surface and the initial deformation length (i.e., the critical instability length). The critical instability length is determined by combining numerical analysis, theoretical calculation, and empirical judgment. Numerical analysis involves establishing a fluid-structure interaction model that considers the strain-softening characteristics of red bed soft rock and the effect of groundwater seepage. The strength reduction method is used to calculate the slope safety factor and predict the failure range, thus determining the numerical solution. In this embodiment, the numerical analysis establishes a fluid-structure interaction model that considers the strain softening characteristics of red bed soft rock and the effect of groundwater seepage. A typical cross-section is selected, and the strength reduction method is used to calculate the safety factor of the slope under natural and saturated conditions, predict the failure range, and determine the numerical solution. ;

[0099] Numerical analysis can be used to calculate the distribution of slope deformation when the slope reaches its ultimate state without any support, thereby predicting the extent of slope failure. The corresponding distance is the horizontal distance from the rear edge of the slope rupture surface to the toe of the slope;

[0100] The theoretical calculations are based on the limit equilibrium theory and the theoretical solution for calculating the softening characteristics of red bed soft rock upon contact with water. And the theoretical calculation is based on the formula:

[0101] Calculate the theoretical solution Lc;

[0102] In the formula: The cohesion (kPa) of the weak interlayer under saturation. The internal friction angle (°) of the weak interlayer under saturated conditions. The unit weight (kN / m³) of the saturated sliding mass rock and soil. The slope excavation height is in meters (m). The dip angle is (°). The slope angle is (°).

[0103] The empirical judgment is based on engineering experience in red bed soft rock to determine the empirical length of the first segment of the bedding-parallel sliding body. In this embodiment, the empirical length is determined by empirically measuring 5 to 10 times the thickness of the bedding plane. , , When <15m, take 15m≤ Linear interpolation is used when the length is <30m. 30m≤ Take 10 at a time ; final decision , , The maximum value of the three is used as the critical instability length in the design. ;

[0104] S3. Calculate the sliding thrust: Considering the strength attenuation characteristics of soft red rock, an improved transfer coefficient method is used to calculate the sliding thrust. Specifically, in this embodiment, the improved transfer coefficient method introduces a strength attenuation coefficient. , Over time change, , As the decay rate constant, the corrected formula for calculating glide thrust is:

[0105] ;

[0106] in, ;

[0107] Let be the remaining sliding thrust (kN / m) at the end of the i-th block. The thrust (kN / m) transmitted from the (i-1)th block. Let be the thrust transfer coefficient from block i-1 to block i. For safety reasons, Let be the weight of the i-th block (kN / m). Let be the inclination angle (°) of the bottom sliding surface of the i-th block. Let be the cohesion (kPa) of the i-th block surface in a saturated state. Let be the internal friction angle (°) of the i-th block surface when it is in a saturated state. Let be the length (m) of the bottom sliding surface of the i-th block.

[0108] S4. Sliding thrust judgment: If the sliding thrust is >2500kN / m, some potential sliding bodies need to be removed along the layer to reduce the thrust. If the sliding thrust is ≤2500kN / m, support should be provided directly. After removing some potential sliding bodies along the layer, the sliding thrust should be ≤2500kN / m. When clearing along the layer, platforms of 2m to 5m should be set up every 40m to 60m.

[0109] S5. A double-row anti-slide pile and prestressed anchor cables are used for comprehensive support of the bedding slope. The anchoring section must be embedded in stable strata. In this embodiment, the double-row anti-slide piles include a front row and a rear row. Both the front and rear rows are made of bored cast-in-place piles with a diameter of 2.0m to 2.5m or square piles with a cross-section of 2×3m. The front row of anti-slide piles should be close to the slope toe, and the distance between the rear and front rows of anti-slide piles is 50m to 80m. In this embodiment, the pile bodies of the front and rear rows of anti-slide piles are made of epoxy resin coated steel bars, and the outer surface of the pile body is treated with a nano-ceramic anti-corrosion layer. A connecting beam is set at the top of the front row of anti-slide piles to form an integral load-bearing structure, and 2 to 3 rows of anchor cables are set starting 1.5m below the pile top, spaced 1.5m apart. The anchoring section of the anchor cables must be located in stable bedrock.

[0110] In this embodiment, the prestressed anchor cable is a tension type anchor cable, and the anchoring section of the anchor cable is embedded in the stable bedrock to a depth of 6-10m. It is equipped with a prestress adjustment device, which adjusts the prestress value in stages according to the strength decay curve of the red bed soft rock. The initial prestress is 80% of the design value, which is adjusted to 100% after 6 months, and then supplemented to 110% after 12 months. In this embodiment, the prestress adjustment device is a hydraulic prestress adjustment device, such as a hydraulic anchor cable tensioner, which uses a hydraulic jack as the actuating element. The hydraulic system drives the anchor to move, thereby achieving precise adjustment of the prestress. The tension of the anchor cable is changed by the hydraulic mechanism, thereby precisely controlling the tension (i.e., prestress) of the anchor cable on the slope.

[0111] S6. A drainage system is set up, including multi-layer drainage holes and slope interception drainage. In this embodiment, the drainage holes in the drainage system penetrate the potential slip surface to a depth of 1m to 2m, and the drainage holes are equipped with permeable pipes and reverse filter layers.

[0112] S7. Slope protection: In this embodiment, after clearing the slope, modified concrete containing Bacillus pasteurellium bacterial solution is sprayed first. After several days (e.g., 7 days), anchor bolts are installed, and then vegetation concrete is sprayed to form a composite protective layer of microbial mineralization reinforcement, anchor bolt anchoring and ecological restoration.

[0113] In one embodiment, the drainage system further includes an intelligent monitoring module and an emergency drainage pump. The intelligent monitoring module can collect groundwater level and drainage flow data in real time, and automatically activate the emergency drainage pump when the water level rises by more than 50 cm / d. The intelligent monitoring module includes a controller, a level sensor, and a drainage flow sensor (such as an electromagnetic flow meter or an ultrasonic flow meter). The controller is electrically connected to the emergency drainage pump, the level sensor, and the drainage flow sensor. The level sensor is used to detect the groundwater level, and the drainage flow sensor is used to detect the drainage flow data. The controller controls the start and stop of the emergency drainage pump based on the signals transmitted from the two sensors.

[0114] In one embodiment, in this embodiment, the critical instability length in S2 Employing a spatiotemporal dual-dimensional computational model:

[0115] Spatially, considering the differences in the degree of soft rock weathering and seepage intensity in the slope crest, middle, and toe regions, the numerical solution is used. Theoretical solution Length of experience Assign dynamic weights based on region (e.g., if the slope toe is highly water-sensitive, increase the L after seepage correction). c (weight)

[0116] In the time dimension, a time coefficient is introduced in conjunction with the slip surface evolution prediction results. , The critical buckling length increases with the rate of slip surface expansion. The corrected formula for calculating the critical buckling length is: , This refers to the time calculated from the completion of slope excavation or the completion of the support system implementation, measured in days. This embodiment can achieve... Spatial differentiation and temporal forward-looking calculations are better suited to the heterogeneous and dynamic evolution characteristics of red bed soft rocks.

[0117] In one embodiment, the calculation of the sliding thrust in S3 incorporates a multi-field coupling correction term for seepage, deformation, and aging. The corrected calculation formula is as follows:

[0118] ;

[0119] in, This is a correction term for the additional force caused by seepage. Real-time pore water pressure; This is a correction term for the surface evolution. The coefficient of the slip surface spread rate. The density of water, The time is calculated from the completion of slope excavation or the completion of the support system, and the unit is days.

[0120] In one embodiment, in S5, fiber optic strain sensors are implanted in the pile bodies of the front and rear anti-slide piles to monitor the pile body bending moment distribution in real time; the anchor cable prestress adjustment device is linked with the pile body strain monitoring data monitored by the fiber optic strain sensors.

[0121] When the bending moment in a certain section of the pile exceeds the design value by 10% (due to stress concentration caused by soft rock deformation), the prestress of the anchor cables in the corresponding area is automatically adjusted (e.g., increasing the anchor cable tension in that area by 5%-10%). The excess bending moment in the pile is offset by the anchor cable tension. This upgrades the system from individual anchor cable force adjustment to pile-anchor coordinated unloading, avoiding local overload on the anti-slide pile, reducing the consumption of ineffective prestress in the anchor cables, and improving the overall stability of the support system.

[0122] In one embodiment, during S7, when spraying modified concrete containing Bacillus pasteurellium bacterial solution, a distributed optical fiber sensing element is incorporated. The diameter of the distributed optical fiber sensing element is <0.5mm, which does not affect the concrete strength, and the strain and crack development status of the protective layer are monitored in real time.

[0123] Temperature-sensitive microbial agent capsules are mixed into the planted concrete. When the temperature is >25℃ or the humidity is >80%, the capsules will automatically rupture and release the microbial liquid. When the strain of the protective layer exceeds the threshold, such as 500με, the microbial agent is released by local spraying to raise the temperature / humidify the area. The microbial mineralization process is then used to automatically repair the micro-cracks.

[0124] This embodiment upgrades the slope protection layer from passively bearing loads to a smart structure that can sense its state and self-repair, thereby extending the protection life and reducing later maintenance costs.

[0125] In one embodiment, in S7, the anchor rod body has a built-in stress sensor and grouting channel to monitor the changes in anchoring force in real time; when the anchoring force decay exceeds 15% of the design value (due to soft rock creep), secondary grouting (injecting cement grout containing bacteria) is automatically started to enhance the anchoring force through the dual effects of cement solidification and microbial mineralization.

[0126] This embodiment can realize real-time monitoring and active compensation of anchoring force, and is adapted to the problem of anchoring force loss caused by long-term creep of red soft rock.

[0127] In one embodiment, such as Figure 2 The image shows a three-dimensional geological model of a long bedding slope. The slope was excavated, and through detailed engineering geological investigation, the rock strata occurrence, weathering characteristics, distribution of weak interlayers, groundwater occurrence and seepage paths, and weak interlayers of the red-bed soft rock bedding slope were determined. , Parameters, establish corresponding geological models; such as Figure 3 The image shows a geological profile model of a long bedding slope. The critical instability length was determined by combining numerical analysis, theoretical calculation, and empirical judgment. That is, to determine the length of the first deformation.

[0128] This embodiment provides a slope protection structure for long bedding-parallel red bed soft rock, combined with Figure 4 The image shows an example of a cross-sectional retaining structure for a long bedding slope. This retaining structure includes:

[0129] In-line clearing and load reduction unit: such as Figure 4 and Figure 5 As shown, the layered clearing and load reduction unit consists of multi-level cut slopes 1 and platforms 2. In this embodiment, platforms 2 are set at the junction of each level of slope 1. The multi-level cut slopes 1 are only for the core unstable area in the middle and rear of the landslide body 1 (rather than the entire area of ​​cut slopes). By reducing the self-weight of the slope 1, the sliding thrust is directly reduced. Compared with the traditional whole-area load reduction, the amount of earthwork can be reduced, and the excavation cost and damage to the original landform can be significantly reduced. The width of each platform 2 is adapted to the construction and protection requirements, which not only provides operating space for subsequent anchor cable construction and slope protection, but also disperses the vertical pressure of the slope 1.

[0130] Double-row anti-slide pile unit: such as Figure 5 and Figure 6As shown, the double-row anti-slide piles include a front row of anti-slide piles 4, a rear row of anti-slide piles 5, and a connecting beam 8. Both the front row of anti-slide piles 4 and the rear row of anti-slide piles 5 are bored cast-in-place piles with a diameter of 2.0m to 2.5m or square piles with a cross section of 2×3m. The front row of anti-slide piles 4 should be close to the toe of the slope, and the distance between the rear row of anti-slide piles 5 and the front row of anti-slide piles 4 is 50m to 80m.

[0131] Both the front row of anti-slide piles 4 and the rear row of anti-slide piles 5 are provided in multiple quantities, such as Figure 6 As shown, in this embodiment, multiple connecting beams 8 are provided, and the two ends of the multiple connecting beams 8 are respectively welded or bolted to the pile tops of two adjacent front row anti-slide piles 4. In this embodiment, the connection beams 8 on the pile tops of the front row anti-slide piles 4 enable multiple front row anti-slide piles 4 to form an integral load-bearing structure, avoid local bending damage caused by uneven load on a single pile, and make the double row of piles form a rigid frame structure, thereby improving the deformation resistance.

[0132] like Figure 5 As shown, prestressed anchor cables 6 are installed on the front row of anti-slide piles 4. The anchoring section of the anchor cable 6 needs to be located in stable bedrock. In this embodiment, 2 to 3 rows of anchor cables 6 are installed starting 1.5m below the top of the front row of anti-slide piles 4, with a spacing of 1.5m.

[0133] Both the front row of anti-slide piles 4 and the rear row of anti-slide piles 5 are treated with anti-corrosion coating. The front row of anti-slide piles 4 directly blocks the movement of shallow sliding bodies, while the rear row of anti-slide piles 5 bears the thrust of deep sliding bodies, forming a double anti-slide barrier that is linked front and rear. This can effectively resist the gradual sliding of the red layer in strata. In this embodiment, the pile body is made of epoxy resin coated steel bars, and the outer surface of the pile is protected by a nano-ceramic anti-corrosion layer, which specifically resists the corrosion of the pile body by acidic groundwater (pH value 3-6) in red layer areas. This avoids the problem of steel bar corrosion that occurs in traditional anti-slide piles after 5-8 years, thus extending the service life and reducing the later maintenance costs.

[0134] Prestressed anchor cable unit: It consists of tension type anchor cable 6, prestress adjustment device and anchoring section. The anchoring section of anchor cable 6 is embedded in stable bedrock. One end of anchor cable 6 is connected to prestress adjustment device. In this embodiment, in addition to setting anchor cable 6 on the front row of anti-slide piles 4, anchor cable 6 can also be set on the rear side of the rear row of anti-slide piles 5 to further enhance the slope installation coefficient.

[0135] In this embodiment, the prestressing adjustment device adopts a hydraulic prestressing adjustment device, such as a hydraulic anchor tensioner. A hydraulic jack is used as the actuator, and the anchor is driven by a hydraulic system to achieve precise adjustment of the prestress. The tension of the anchor cable is changed by the hydraulic mechanism, thereby precisely controlling the tension (i.e., prestress) of the anchor cable on the slope. The prestressing adjustment device can adjust the prestress in stages according to the strength decay law of the red bed soft rock. The initial low prestress avoids excessive instantaneous stress on the soft rock, preventing plastic deformation. Later, as the strength decays, the prestress is gradually increased to maintain sufficient active anti-sliding force. Compared with a fixed prestress design, this scheme can reduce the risk of anchor cable failure. The prestressing adjustment device and the double-row anti-sliding piles form a combined force mode of rigid anti-sliding and flexible tension. The active tension of the anchor cable can offset part of the sliding thrust, reducing the load on the anti-sliding piles and effectively improving the overall safety factor of the slope.

[0136] Drainage unit: combined Figure 4 and Figure 5 As shown, the drainage unit includes multiple layers of drainage holes 7 and a slope interception drainage structure. The drainage holes 7 penetrate 1m-2m into the potential slip surface, combined with... Figure 7 As shown, the drain hole 7 is equipped with a permeable pipe 700 and a filter layer. The filter layer is located between the permeable pipe 700 and the drain hole 7. In this embodiment, it is combined with... Figure 7 As shown, the filter layer includes an inner layer 710 and an outer layer 720. The inner layer 710 is geotextile, and the outer layer 720 is quartz sand or gravel. The inner layer 710 wraps around the outside of the permeable pipe 700, and the outer layer 720 fills the space between the inner layer 710 and the hole wall of the drainage hole 7.

[0137] In this embodiment, the slope interception and drainage structure is a water interception ditch 3. The water interception ditch 3 is set at the bottom of the slope surface of each level of slope 1 and is located on each level of platform 2. The water interception ditch 3 on platform 2 can quickly collect the slope surface water and prevent rainwater from directly scouring the slope 1 or seeping down and softening the soft rock.

[0138] Slope protection unit: It consists of a modified concrete layer containing bacterial solution, anchor bolts, and a vegetated concrete layer. In this embodiment, after clearing the slope, modified concrete containing Bacillus pasteurellium bacterial solution is sprayed first. After several days, anchor bolts are installed, and then vegetated concrete is sprayed to form a composite protective layer of microbial mineralization reinforcement, anchor bolt anchoring, and ecological restoration.

[0139] In one embodiment, such as Figure 4As shown, a gully is constructed at the lower part of the slope. This gully drains seepage water from within the slope and concentrates rainwater and surface water flowing from the slope surface into the gully, preventing water from scouring the slope surface indiscriminately or flowing along the toe, thus reducing slope erosion and toe scouring. The soil and rock mass of slopes often contains groundwater or water formed by rainwater infiltration. This water reduces the strength of the soil and rock mass, increases the weight of the slope, and may also generate dynamic water pressure, easily triggering landslides. The gully, as a drainage channel, can quickly remove water from the lower part of the slope, reducing pore water pressure within the slope and further reducing the risk of landslides and collapses.

[0140] It should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A design method for slope protection of long bedding-parallel red bed soft rock, characterized in that, Includes the following steps: S1. Geological model establishment; S2. Determine the slip surface and initial deformation length: Determine the critical instability length using a combination of numerical analysis, theoretical calculation, and empirical judgment. The numerical analysis involves establishing a fluid-structure interaction model that considers the strain softening characteristics of red bed soft rock and the effect of groundwater seepage. The strength reduction method is used to calculate the slope safety factor and predict the failure range, thus determining the numerical solution. ; The theoretical calculations are based on the limit equilibrium theory and the theoretical solution for calculating the softening characteristics of red bed soft rock upon contact with water. ; The empirical judgment is based on engineering experience in red bed soft rock to determine the empirical length of the first segment of the bedding-parallel sliding body. Ultimately , , The maximum value of the three is used as the critical instability length in the design. ; S3. Calculate the sliding thrust: Considering the strength attenuation characteristics of red bed soft rock, the improved transfer coefficient method is used to calculate the sliding thrust. S4. Determine the sliding thrust. If the sliding thrust is greater than 2500 kN / m, some potential sliding bodies need to be removed along the layer to reduce the thrust. If the sliding thrust is less than or equal to 2500 kN / m, support should be applied directly. S5. Double-row anti-slide piles and prestressed anchor cables are used to provide comprehensive support for the bedding slope. S6. Install a drainage system, including multi-layer drainage holes and slope surface interception drainage; S7. Slope protection.

2. The design method for slope protection of long bedding-parallel red soft rock as described in claim 1, characterized in that, Based on detailed engineering geological surveys, S1 clarified the strata occurrence, weathering characteristics, distribution of weak interlayers, groundwater occurrence and seepage paths, and weak interlayers of the red-bed soft rock bedding slope. , Parameters, establish corresponding geological models, This represents the cohesion of the weak interlayer under saturated conditions. It represents the internal friction angle of the weak interlayer under saturated conditions.

3. The design method for slope protection of long bedding-parallel red soft rock as described in claim 1, characterized in that, In S2, the numerical analysis establishes a fluid-structure interaction model considering the strain softening characteristics of red bed soft rock and the effect of groundwater seepage. A typical cross-section is selected, and the strength reduction method is used to calculate the safety factor of the slope under natural and saturated conditions, thus determining the numerical solution. ; The theoretical calculation formula is: ； In the formula: The cohesion (kPa) of the weak interlayer under saturation. The internal friction angle (°) of the weak interlayer under saturation. The unit weight (kN / m³) of the saturated sliding mass rock and soil. The slope excavation height is in meters (m). The dip angle is (°). The slope angle is (°). Empirical judgment is based on determining the empirical length as 5 to 10 times the thickness of the bedding plane. , , When <15m, take 15m≤ Linear interpolation is used when the length is <30m. 30m≤ Take 10 at a time .

4. The design method for slope protection of long bedding-parallel red soft rock as described in claim 1, characterized in that, The improved transfer coefficient method introduces an intensity attenuation coefficient. , Over time change, , As the decay rate constant, the corrected formula for calculating glide thrust is: ； in, ; Let be the remaining sliding thrust (kN / m) at the end of the i-th block. The thrust (kN / m) transmitted from the (i-1)th block. Let be the thrust transfer coefficient from block i-1 to block i. For safety reasons, Let be the weight of the i-th block (kN / m). Let be the inclination angle (°) of the bottom sliding surface of the i-th block. Let be the cohesion (kPa) of the i-th block surface in a saturated state. Let be the internal friction angle (°) of the i-th block surface when it is in a saturated state. Let be the length (m) of the bottom sliding surface of the i-th block.

5. The design method for slope protection of long bedding-parallel red soft rock as described in claim 1, characterized in that, S4. Sliding thrust judgment: If the sliding thrust is >2500kN / m, some potential sliding bodies need to be removed along the layer to reduce the thrust. If the sliding thrust is ≤2500kN / m, it can be directly supported. After removing some potential sliding bodies along the layer, the sliding thrust should be ≤2500kN / m. When clearing along the layer, a 2m to 5m platform should be set every 40m to 60m. S5. Double-row anti-slide piles, including a front row and a rear row of anti-slide piles. Both the front and rear rows of anti-slide piles are made of bored cast-in-place piles with a diameter of 2.0m to 2.5m or square piles with a cross-section of 2×3m. The front row of anti-slide piles should be close to the toe of the slope, and the distance between the rear row of anti-slide piles and the front row of anti-slide piles should be 50m to 80m. A connecting beam is set at the top of the front row of anti-slide piles to form an integral load-bearing structure, and 2 to 3 rows of anchor cables are set starting 1.5m below the top of the piles, with a spacing of 1.5m. The anchoring section of the anchor cables must be located in stable bedrock. The prestressed anchor cables are tension type, with the anchorage section embedded in stable bedrock to a depth of 6m~10m. They are equipped with a prestress adjustment device to adjust the prestress value in stages according to the strength decay curve of the red bed soft rock. The initial prestress is 80% of the design value, adjusted to 100% after 6 months, and further increased to 110% after 12 months. S6. The drainage hole in the drainage system penetrates the potential slip surface to a depth of 1m to 2m. The drainage system also includes an intelligent monitoring module and an emergency drainage pump. The intelligent monitoring module can collect groundwater level and drainage flow data in real time. When the water level rises by more than 50cm / d, the emergency drainage pump is automatically started. S7. Slope protection: After clearing the slope, first spray modified concrete containing Bacillus pasteurization solution onto the slope, then insert anchor bolts several days later, and finally spray vegetated concrete to form a composite protective layer of microbial mineralization reinforcement, anchor bolt anchoring, and ecological restoration.

6. A method for designing support for long bedding slopes in red-bed soft rock according to claim 1 or 3, characterized in that, S2 Critical instability length Employing a spatiotemporal dual-dimensional computational model: In the spatial dimension, considering the differences in the degree of soft rock weathering and seepage intensity in the slope crest, middle, and toe regions, the numerical solution is used to... Theoretical solution Length of experience Assign dynamic weights based on region; In the time dimension, a time coefficient is introduced in conjunction with the slip surface evolution prediction results. , The critical buckling length increases with the rate of slip surface expansion. The corrected formula for calculating the critical buckling length is: , The time is calculated from the completion of slope excavation or the completion of the support system, and the unit is days.

7. The design method for slope protection of long bedding-parallel red soft rock as described in claim 4, characterized in that, The calculation of the sliding thrust in S3 incorporates a multi-field coupling correction term for seepage, deformation, and aging. The corrected calculation formula is as follows: ； in, This is a correction term for the additional force caused by seepage. Real-time pore water pressure; This is a correction term for the surface evolution. The coefficient of the slip surface spread rate. The density of water, The time is calculated from the completion of slope excavation or the completion of the support system, and the unit is days.

8. A red bed soft rock long bedding slope support structure for use in any one of the design methods for red bed soft rock long bedding slopes according to claims 1-7, characterized in that, include: Layered clearing and load reduction unit: consists of multi-stage cut slopes and platforms; Double-row anti-slide pile unit: includes front row anti-slide piles, rear row anti-slide piles and connecting beams. There are multiple front row anti-slide piles and multiple rear row anti-slide piles. The two ends of the connecting beam are respectively connected to two adjacent front row anti-slide piles. Prestressed anchor cables are installed on the front row anti-slide piles. Prestressed anchor cable unit: It consists of a tension anchor cable, a prestress adjustment device and an anchoring section. The anchoring section is embedded in stable bedrock, and one end of the anchor cable is connected to the prestress adjustment device. Drainage unit: includes multiple drainage holes and slope interception drainage structure. The drainage holes penetrate the potential slip surface. The drainage holes are equipped with permeable pipes and reverse filter layers. The reverse filter layer is located between the permeable pipes and the drainage holes. The slope interception drainage structure is a water interception ditch. The water interception ditch is set at the bottom of the slope of each level of the slope. Slope protection unit: consists of a modified concrete layer containing bacterial solution, anchor bolts, and a vegetation concrete layer.

9. A long bedding slope support structure for red bed soft rock according to claim 8, characterized in that, The filter layer includes an inner layer and an outer layer. The inner layer is geotextile, and the outer layer is quartz sand or gravel. The inner layer wraps around the outside of the permeable pipe, and the outer layer fills the space between the inner layer and the wall of the drainage hole.

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