An underground water-sealed storage crossing intersection surrounding rock stability control method and system based on reserved rock pillar optimization

Abstract

The application discloses a kind of based on underground water seal cavern intersection surrounding rock stability control method and system of optimization of reserved rock column, belong to underground water seal cavern and large underground cavern surrounding rock stability control technical field.For the problem that weak zone cuts into main cavern and process shaft intersection is prone to surrounding rock deformation concentration, plastic zone expansion and stress anomaly, the application obtains intersection section geological space parameter, surrounding rock mechanics parameter and excavation structure parameter, constructs three-dimensional numerical calculation model including main cavern, process shaft, weak zone and reserved rock column to be optimized, sets multiple reserved rock column width working conditions for numerical calculation, constructs comprehensive evaluation function to determine the width of reserved rock column, and accordingly retains reserved rock column and sets side drift or auxiliary drift to change construction path, while dynamically correcting subsequent construction parameters according to construction monitoring data.The application can improve the stability of surrounding rock and construction safety of weak zone intersection section.

Description

Technical Field

[0001] This invention belongs to the field of underground water-sealed caverns and large underground cavern surrounding rock stability control technology, and particularly relates to a method and system for controlling the surrounding rock stability at the intersection of underground water-sealed caverns based on pre-reserved rock pillar optimization. Background Technology

[0002] Water-sealed underground caverns are typically buried within stable underground rock masses, relying on natural groundwater pressure to create a water seal and prevent leakage of the stored medium. These projects are characterized by large cavern spans, significant depths, complex intersecting relationships among caverns, multiple excavation steps, and high operational safety requirements. The main cavern, process shafts, construction tunnels, connecting tunnels, and auxiliary caverns form spatially intersecting structures in localized areas, subjecting the surrounding rock to multi-directional excavation unloading, stress redistribution, and the combined effects of locally weakened rock masses.

[0003] A weakened zone refers to a low-strength surrounding rock area formed by alteration zones, fracture zones, densely jointed zones, weak interlayers, and their combinations. Such weakened zones typically exhibit poor integrity, low deformation modulus, low cohesion, low shear strength, and sensitivity to softening in water. When a weakened zone intersects, cuts into, or crosses the outline of the main tunnel, it can easily lead to increased surrounding rock displacement, expansion of the plastic zone, stress concentration at the sidewalls and arch shoulders, uneven stress on the support structure, and an increased risk of local instability at the intersection.

[0004] Existing methods for treating intersections of underground caverns often employ measures such as reinforcing anchor bolts, thickening shotcrete layers, densifying steel mesh, installing steel supports, or shortening excavation advances. While these methods can improve support strength to some extent, they typically rely on experience to determine support parameters and lack quantitative evaluation of the rock mass width that should be retained between the main cavern and the weakened zone. Furthermore, conventional excavation paths may directly disturb high-risk sections of the weakened zone, leading to adverse deformation and stress concentration in the support structure.

[0005] Taking the weakened zone at a typical underground water-sealed cavern intersection as an example, the elastic modulus of the affected area can be significantly lower than that of the general surrounding rock area, and the shear strength is also significantly reduced. This difference indicates that if empirical reinforcement is still used without coordinating and optimizing the reserved rock column width, construction path, and monitoring feedback, it will be difficult to reduce the impact of the weakened zone on the stability of the surrounding rock at the intersection from the source.

[0006] Therefore, there is an urgent need to propose a method and system for controlling the stability of the surrounding rock at the intersection of underground water-sealed caverns, which can combine the spatial relationship of the weakened zone, the mechanical parameters of the surrounding rock, the reserved rock column width, multi-index stability evaluation and monitoring feedback correction, so as to achieve quantitative evaluation, active intervention and dynamic closed-loop control of the stability of the surrounding rock at the intersection. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on pre-reserved rock pillars, comprising the following steps: Obtain the geological spatial parameters, surrounding rock mechanical parameters, and excavation structure parameters of the intersection section; Based on the geological spatial parameters, the surrounding rock mechanical parameters, and the excavation structure parameters, a three-dimensional numerical calculation model is constructed, including the main tunnel, process shaft, weakened zone, and reserved rock pillars to be optimized. Based on the three-dimensional numerical calculation model, multiple sets of reserved rock column width working conditions are set, and numerical calculations are performed on each set of reserved rock column width working conditions to obtain the surrounding rock response index under each set of reserved rock column width working conditions. Based on the surrounding rock response index, a comprehensive evaluation function is constructed, and the comprehensive evaluation function is used to comprehensively evaluate the reserved rock column width working conditions of each group in order to determine the reserved rock column width. Based on the determined reserved rock column width, reserved rock columns are retained in the intersection section, and side guide tunnels or auxiliary guide tunnels are set up to change the construction path; During construction, monitoring data is acquired, and subsequent construction parameters are dynamically corrected based on the monitoring data.

[0008] Optionally, the weakened zone includes alteration zone, fracture zone, densely jointed zone, weak interlayer, and low-strength surrounding rock area formed by their combination; The geological spatial parameters include the spatial relationship between the weakened zone and the main cavern, the spatial relationship between the weakened zone and the process shaft, the spatial relationship between the weakened zone and the connecting cavern, the width of the weakened zone, the orientation of the weakened zone, the dip angle of the weakened zone, the distance from the boundary of the weakened zone to the outline of the main cavern, and the local surrounding rock grade of the intersection section.

[0009] Optionally, the surrounding rock mechanical parameters include density, bulk modulus, shear modulus, cohesion, internal friction angle, and tensile strength; the three-dimensional numerical calculation model adopts an elastoplastic constitutive model and divides the surrounding rock into a general surrounding rock zone and a weakened zone.

[0010] Optionally, the equivalent elastic modulus and Poisson's ratio are calculated based on the bulk modulus and the shear modulus, and the degree of reduction in deformation parameters of the weakened zone relative to the general surrounding rock zone is determined based on the equivalent elastic modulus and the Poisson's ratio.

[0011] Optionally, based on the Mohr-Coulomb strength criterion, the shear strength of the general surrounding rock zone and the weakened zone influence zone is calculated according to the cohesion, normal stress and internal friction angle, and the degree of strength reduction of the weakened zone influence zone relative to the general surrounding rock zone is determined according to the shear strength.

[0012] Optionally, the surrounding rock response index includes a displacement control rate, which is the difference between the maximum displacement of the surrounding rock under the condition of no reserved rock pillar and the maximum displacement of the surrounding rock under the condition of current reserved rock pillar width, divided by the maximum displacement of the surrounding rock under the condition of no reserved rock pillar, and then multiplied by 100%.

[0013] Optionally, the surrounding rock response index includes a plastic zone control coefficient, which is the difference between the area or volume of the plastic zone under the condition of no reserved rock pillar and the area or volume of the plastic zone under the condition of current reserved rock pillar width, divided by the area or volume of the plastic zone under the condition of no reserved rock pillar, and then multiplied by 100%.

[0014] Optionally, the surrounding rock response index includes the maximum shear stress fluctuation coefficient, which is the difference between the maximum shear stress peak value and the minimum shear stress peak value, divided by the average value of the maximum shear stress, and then multiplied by 100%.

[0015] Optionally, the comprehensive evaluation function is constructed based on displacement normalized evaluation values, plastic zone normalized evaluation values, volumetric stress or stress stability normalized evaluation values, maximum shear stress normalized evaluation values, and construction adaptability evaluation values; each of the evaluation values ​​is obtained by performing range normalization processing on the corresponding original surrounding rock response indicators under the reserved rock column width conditions of each group; the value of the comprehensive evaluation function is the sum of the products of each of the evaluation values ​​and their respective preset weight coefficients, and the sum of each of the preset weight coefficients is 1.

[0016] This invention also provides a stability control system for the surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization, comprising: The parameter acquisition module is used to acquire the geological spatial parameters, surrounding rock mechanical parameters, and excavation structure parameters of the intersection section. The model building module is used to construct a three-dimensional numerical calculation model including the main tunnel, process shaft, weakened zone and reserved rock pillar to be optimized, based on the geological spatial parameters, the surrounding rock mechanical parameters and the excavation structure parameters. The working condition calculation module is used to set multiple sets of reserved rock column width working conditions according to the three-dimensional numerical calculation model, and to perform numerical calculations on each set of reserved rock column width working conditions to obtain the surrounding rock response index under each set of reserved rock column width working conditions. The index evaluation module is used to construct a comprehensive evaluation function based on the surrounding rock response index, and to use the comprehensive evaluation function to comprehensively evaluate the reserved rock column width working conditions of each group in order to determine the reserved rock column width. The path optimization module is used to retain the reserved rock pillar in the intersection section according to the width of the reserved rock pillar, and to set up side guide tunnels or auxiliary guide tunnels to change the construction path; The feedback correction module is used to acquire monitoring data during construction and dynamically correct subsequent construction parameters based on the monitoring data.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects: First, this invention determines the width of the reserved rock pillar through multi-condition numerical calculations and comprehensive evaluation functions, avoiding reliance on experience to select the rock pillar size and improving the quantification of surrounding rock stability control at complex intersections. Second, this invention uses the reserved rock pillar as a load-bearing isolation unit and deformation coordination unit between the main tunnel and the weakened zone, which can weaken the direct impact of the weakened zone on the main tunnel and reduce the risk of plastic zone penetration and local displacement concentration. Third, this invention changes the construction path of the intersection through side guide tunnels or auxiliary guide tunnels, allowing the main excavation disturbance to avoid high-risk sections of the weakened zone, thus improving the construction safety of the intersection between the process shaft and the main tunnel. Fourth, this invention corrects the support parameters and excavation sequence through monitoring and feedback, enabling timely identification of abnormal surrounding rock response and the implementation of reinforcement measures during construction, thereby improving the stability of the intersection during construction and operation. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention; Figure 2 This is a schematic diagram showing the spatial relationship between the main cavern, process shaft, weakened zone, reserved rock pillar, side guide tunnel, and partially preserved rock wall of the underground water-sealed cavern according to an embodiment of the present invention. Figure 3 This is a schematic diagram illustrating the calculation relationship of the reserved rock column width under the condition that the weakened zone cuts into the main cavern according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the three-dimensional numerical model and typical cross-section extraction location under different reserved rock column widths in an embodiment of the present invention; In the diagram: 1. Main cavern; 2. Process shaft; 3. Weakened zone; 4. Reserved rock pillar; 5. Side guide tunnel; 6. Partially preserved rock wall; 7. Main cavern axis; 8. Weakened zone cutting direction. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0021] Example 1 like Figure 1 As shown, this embodiment provides a method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization, including the following steps: Obtain the geological spatial parameters, surrounding rock mechanical parameters, and excavation structure parameters of the intersection section; Based on the geological spatial parameters, the surrounding rock mechanical parameters, and the excavation structure parameters, a three-dimensional numerical calculation model is constructed, including the main tunnel 1, the process shaft 2, the weakened zone 3, and the reserved rock pillar 4 to be optimized. Based on the three-dimensional numerical calculation model, multiple sets of reserved rock column width working conditions are set, and numerical calculations are performed on each set of reserved rock column width working conditions to obtain the surrounding rock response index under each set of reserved rock column width working conditions. Based on the surrounding rock response index, a comprehensive evaluation function is constructed, and the comprehensive evaluation function is used to comprehensively evaluate the reserved rock column width working conditions of each group in order to determine the reserved rock column width. Based on the determined reserved rock column width, reserved rock columns are retained in the intersection section, and side guide tunnels 5 or auxiliary guide tunnels are set up to change the construction path; During construction, monitoring data is acquired, and subsequent construction parameters are dynamically corrected based on the monitoring data.

[0022] Furthermore, the weakened zone includes alteration zones, fracture zones, densely jointed zones, weak interlayers, and low-strength surrounding rock areas formed by their combinations; The geological spatial parameters include the spatial relationship between the weakened zone and the main cavern, the spatial relationship between the weakened zone and the process shaft, the spatial relationship between the weakened zone and the connecting cavern, the width of the weakened zone, the orientation of the weakened zone, the dip angle of the weakened zone, the distance from the boundary of the weakened zone to the outline of the main cavern, and the local surrounding rock grade of the intersection section.

[0023] Furthermore, the surrounding rock mechanical parameters include density, bulk modulus, shear modulus, cohesion, internal friction angle, and tensile strength; the three-dimensional numerical calculation model adopts an elastoplastic constitutive model and divides the surrounding rock into a general surrounding rock zone and a weakened zone.

[0024] Furthermore, the equivalent elastic modulus and Poisson's ratio are calculated based on the bulk modulus and the shear modulus, and the degree of reduction in deformation parameters of the weakened zone relative to the general surrounding rock zone is determined based on the equivalent elastic modulus and the Poisson's ratio.

[0025] (1) (2) Where E is the equivalent elastic modulus, ν is Poisson's ratio, K is the bulk modulus, and G is the shear modulus.

[0026] Furthermore, based on the Mohr-Coulomb strength criterion, the shear strength of the general surrounding rock zone and the weakened zone influence zone is calculated according to the cohesion, normal stress and internal friction angle, and the degree of strength reduction of the weakened zone influence zone relative to the general surrounding rock zone is determined according to the shear strength.

[0027] (3) Where τf is the shear strength, c is the cohesion, σn is the normal stress, and φ is the internal friction angle.

[0028] Furthermore, the surrounding rock response index includes the displacement control rate, which is the difference between the maximum displacement of the surrounding rock under the condition of no reserved rock pillar and the maximum displacement of the surrounding rock under the condition of the current reserved rock pillar width, divided by the maximum displacement of the surrounding rock under the condition of no reserved rock pillar, and then multiplied by 100%.

[0029] (4) Furthermore, the surrounding rock response index includes a plastic zone control coefficient, which is the difference between the area or volume of the plastic zone under the condition of no reserved rock pillar and the area or volume of the plastic zone under the condition of current reserved rock pillar width, divided by the area or volume of the plastic zone under the condition of no reserved rock pillar, and then multiplied by 100%.

[0030] (5) Furthermore, the surrounding rock response index includes the maximum shear stress fluctuation coefficient, which is the difference between the maximum shear stress peak value and the minimum shear stress peak value, divided by the average value of the maximum shear stress, and then multiplied by 100%.

[0031] (6) Where, η u (w) represents the displacement control law, η p (w) is the control coefficient of the plastic zone, η τ The maximum shear stress fluctuation coefficient; u0 and u wThese represent the maximum displacements of the surrounding rock under the conditions of no pre-reserved rock pillar and a pre-reserved rock pillar with a width of w, respectively; A0 and A w These represent the area or volume of the plastic zone under the conditions of no pre-reserved rock pillar and a pre-reserved rock pillar with a width of w, respectively; τ max τ min and These represent the peak value of maximum shear stress, the peak value of minimum shear stress, and the average value of maximum shear stress, respectively.

[0032] Furthermore, the comprehensive evaluation function is constructed based on displacement normalized evaluation values, plastic zone normalized evaluation values, volumetric stress or stress stability normalized evaluation values, maximum shear stress normalized evaluation values, and construction adaptability evaluation values. Each of the evaluation values ​​is obtained by performing range normalization processing on the corresponding original surrounding rock response indicators under the reserved rock column width conditions of each group. The value of the comprehensive evaluation function is the sum of the products of each evaluation value and its corresponding preset weight coefficient, and the sum of each preset weight coefficient is 1.

[0033] (7) (8) Where F(w) is the comprehensive evaluation value of the reserved rock column with width w, and R u (w), R p (w), R σ (w), R τ (w), R c (w) represents the normalized evaluation values ​​of displacement, plastic zone, stress stability, maximum shear stress, and construction adaptability, respectively, and α1, α2, α3, α4, and α5 are preset weighting coefficients.

[0034] (9) Among them, R i (w) is the normalized value of the i-th indicator, X i (w) is the i-th original index when the width is w, X i,min and X i,max These are the minimum and maximum values ​​of this indicator under all reserved rock column width conditions.

[0035] The original indicators that indicate better evaluation results with smaller values ​​are reverse normalized, while the original indicators that indicate better evaluation results with larger values ​​are forward normalized, so that each normalized evaluation value satisfies the following: the larger the value, the better the corresponding working condition, and the larger the value of the comprehensive evaluation function F(w), the better the comprehensive performance of the five indicators.

[0036] Furthermore, the side guide tunnel or auxiliary guide tunnel is set between the process shaft and the main cavern, and its cross-sectional shape is one of rectangular, city gate-shaped, or straight-walled arch, and the cross-sectional dimensions are determined according to the construction equipment, surrounding rock grade, and support operation space; the reserved rock pillar is located between the weakened zone and the main cavern, serving as a load-bearing isolation unit and deformation coordination unit.

[0037] Furthermore, the dynamic correction includes: when the monitoring indicators exceed the preset threshold, taking reinforcement support measures and / or adjusting the excavation sequence; the monitoring indicators include one or more of the following: surrounding rock displacement rate, anchor bolt axial force growth rate, steel plate stress growth rate, support structure stress growth rate, and maximum shear stress fluctuation coefficient.

[0038] The following description focuses on a section at the intersection of a water-sealed underground cavern. In this section, the weakened zone and the main cavern are spatially adjacent, with a local section intersecting the process shaft and the main cavern. The main cavern has a straight-walled, arched cross-section, with an excavation width of approximately 20m and a height of approximately 30m; the weakened zone and the main cavern are obliquely intersecting axially. (For example...) Figure 3 As shown, with the main cavern axis 7 as the reference, the weakened zone obliquely intersects the main cavern outline along the cutting direction 8 at a certain angle θ. In some sections, the weakened zone has not yet intersected the main cavern, while in others, it has begun to intersect or significantly intrude into the main cavern outline. The angle θ between the weakened zone cutting direction 8 and the main cavern axis 7 directly determines the geometric shape of the intersection between the weakened zone and the main cavern, thus affecting the calculation boundary conditions for the reserved rock column width. The weakened zone width B is the net width perpendicular to both sides of the weakened zone boundary. The minimum net distance between the weakened zone boundary and the main cavern outline is defined as the reserved rock column width w.

[0039] First, the mechanical parameters of the general surrounding rock zone and the weakened zone influence zone in the intersection section were obtained. For the general surrounding rock zone, the parameters were: density 2430 kg / m³, bulk modulus 4.43 GPa, shear modulus 2.66 GPa, cohesion 2.19 MPa, internal friction angle 42.7°, and tensile strength 1.50 MPa. For the weakened zone influence zone, the parameters were: density 2320 kg / m³, bulk modulus 0.0869 GPa, shear modulus 0.0268 GPa, cohesion 0.048 MPa, internal friction angle 24.9°, and tensile strength 0.084 MPa.

[0040] Secondly, the equivalent elastic modulus and Poisson's ratio of the general surrounding rock zone and the weakened zone are calculated according to equations (1) and (2). For the general surrounding rock zone, the calculation process is as follows: (10) (11) For the weakened zone, the calculation process is as follows: (12) (13) The ratio of the elastic modulus of the weakened zone to that of the general surrounding rock zone is: (14) The above results indicate that the deformation modulus of the weakened zone is significantly lower than that of the general surrounding rock area, which is a major reason for the localized deformation concentration and expansion of the plastic zone at the intersection. These deformation parameter reduction results support the technical characteristic of judging the degree of deformation parameter reduction in the weakened zone using equivalent elastic modulus and Poisson's ratio.

[0041] Next, under the condition of normal stress σn = 1.0 MPa, the shear strength of the general surrounding rock zone and the weakened zone is calculated according to equation (3). The shear strength of the general surrounding rock zone is: (15) The shear strength of the weakened zone is: (16) The ratio of the shear strength of the weakened zone to the shear strength of the general surrounding rock zone is: (17) The above results indicate that the shear resistance of the weakened zone is significantly lower than that of the general surrounding rock area, and it is more prone to shear failure under multi-directional excavation disturbance and local unloading conditions. These strength reduction calculation results support the technical characteristics for evaluating the degree of strength reduction in the weakened zone using the Mohr-Coulomb strength criterion.

[0042] Then, a three-dimensional numerical model was established, including the main tunnel, process shaft, weakened zone, reserved rock pillars, and intersection structure. The model range was set to 140m in the X direction, 90m in the Y direction, and 130m in the Z direction. Mesh refinement was applied near the main tunnel outline, near the weakened zone, and in the core area of ​​the intersection. Normal displacement constraints were applied to the side boundaries of the model, vertical displacement constraints were applied to the bottom, and the top was a free boundary, with self-weight stress considered. The main tunnel was excavated layer by layer according to the construction sequence to simulate the unloading and stress redistribution of the surrounding rock caused by actual excavation.

[0043] Next, as Figure 4 As shown, six reserved rock column widths of 0m, 1m, 2m, 3m, 4m, and 5m are set up for each working condition, and the plastic zone, displacement, volumetric stress, and maximum shear stress of the surrounding rock in a typical cross-section are calculated respectively. The above widths are only candidate working conditions in this embodiment; in other projects, no less than three sets of candidate width working conditions can be set according to the main tunnel span, the width of the weakened zone, and the construction space conditions. This working condition setting method corresponds to "multiple sets of reserved rock column width working conditions".

[0044] For section K0+997, where the weakened zone has not yet clearly cut into the outline of the main cavern, the maximum displacement is 24.84 mm without a reserved rock pillar; when the width of the reserved rock pillar is 2 m, the maximum displacement is 19.72 mm. Therefore, according to equation (4), the displacement control rate is: (18) When the width of the reserved rock pillar is 5m, the maximum displacement is 14.88mm, then the displacement control rate is: (19) The above calculation results of displacement control rate verify the rationality of using displacement control rate as one of the comprehensive evaluation indicators, and provide a quantitative basis for determining the optimal reserved rock column width.

[0045] For section K1+037, where the weakened zone begins to cut into the main chamber outline, the maximum displacement is 44.52 mm without a reserved rock pillar; when the width of the reserved rock pillar is 1 m, the maximum displacement is 44.33 mm. Therefore, the displacement control rate is: (20) When the width of the reserved rock column is 2m, the maximum displacement is 45.57mm, then the displacement control rate is: (twenty one) When the width of the reserved rock pillar is 5m, the maximum displacement is 22.09mm, then the displacement control rate is: (twenty two) The above results indicate that when the weakened zone begins to intrude into the main cavern outline, the surrounding rock displacement response no longer exhibits a simple, monotonically changing pattern with increasing rock column width. A comprehensive evaluation combining factors such as the plastic zone, stress stability, strength reduction, and construction adaptability is necessary. These results support the necessity of constructing a comprehensive evaluation function using multidimensional indicators.

[0046] In this embodiment, a comprehensive evaluation function is constructed using five indicators: displacement, plastic zone, stress stability, maximum shear stress, and construction adaptability. If the importance of each indicator in the project is equivalent, an initial evaluation can be conducted using equal weights. If the deformation control requirements at the intersection are high, the weight of the displacement indicator is increased. If the weakened zone has a significant reduction in shear strength compared to the general surrounding rock zone and a high risk of shear failure, the weights of the stress stability and maximum shear stress indicators are increased. If construction space and support feasibility are the main limiting factors, the weight of the construction adaptability indicator is increased.

[0047] To further quantitatively compare different reserved rock column widths under various working conditions, this embodiment, based on the aforementioned five-index comprehensive evaluation method, selects three more directly statistically relevant indices—surrounding rock displacement, volumetric stress, and maximum shear stress—to construct a quantitative comprehensive response index. Specifically, three typical cross-sections—K0+997, K1+037, and K1+067—were selected, and response data from 12 key locations—the middle of the arch crown, the middle of the base plate, the left arch shoulder, and the right arch shoulder—were extracted. The average values ​​of each index under different working conditions were calculated and normalized. The plastic zone was used to characterize the failure range, morphology, and connectivity features, serving as an auxiliary stability criterion; construction adaptability was verified based on construction space, equipment access conditions, and support feasibility. The three-index quantitative comprehensive response index is used to verify the optimal results of this embodiment and does not constitute a limitation on the aforementioned five-index comprehensive evaluation method. The comprehensive response evaluation results of the surrounding rock under different reserved rock column widths are shown in Table 1.

[0048] Table 1 Note: , and These are the normalized response exponents for displacement, volumetric stress, and maximum shear stress, respectively; in this embodiment, the three indices are weighted equally. , The smaller the value, the better the overall performance of the three quantitative indicators.

[0049] Table 1 shows the quantitative comprehensive response index of the three indicators for the 3 m working condition. The minimum value of 0.1241 indicates that this working condition performs optimally under the weighted evaluation of the three indices: surrounding rock displacement, volumetric stress, and maximum shear stress. Considering the distribution and connectivity characteristics of the plastic zone under different working conditions, and taking into account construction space and support feasibility, the 3-m reserved rock column exhibits good coordination between surrounding rock deformation control, local stress adjustment, and engineering implementation conditions. Therefore, it can be considered the preferred reserved rock column width for the corresponding intersection section in this embodiment.

[0050] After determining the optimal reserved rock column width, a side guide tunnel (such as...) is set between the process shaft and the main cavern. Figure 2(As shown). One end of the side guide tunnel connects to the process shaft, and the other end connects to the main cavern or a partial guide tunnel within the main cavern; its cross-sectional shape and dimensions are determined based on the construction equipment, surrounding rock grade, and support work space. The axis of the side guide tunnel is preferentially arranged outside the high-risk section of the weakened zone, so that the main construction path avoids the most unfavorable position of the weakened zone, while pre-reserved rock pillars are retained between the weakened zone and the main cavern. In addition, at the connection points between the process shaft and the side guide tunnel, the connection points between the side guide tunnel and the main cavern, and adjacent sections of the weakened zone, partial retainable rock walls 6 can be retained according to the needs of phased excavation and local support. The partially retained rock walls serve as temporary load-bearing units and spatial separation units during construction, used to maintain local surrounding rock stability before the expansion excavation of the side guide tunnel or the secondary lining construction at the intersection; after the support structure of the adjacent parts has formed bearing capacity, the partially retained rock walls are then broken down in stages according to the monitoring and measurement results. This path optimization method corresponds to the technical characteristics of the synergistic effect of the side guide tunnel or auxiliary guide tunnel and the pre-reserved rock pillars.

[0051] A staged excavation simulation was conducted for the side guide tunnel connection scheme. If the maximum shear stresses in the second, third, and fourth stages are 4.28 MPa, 4.24 MPa, and 4.31 MPa, respectively, then the average maximum shear stress is: (twenty three) (twenty four) The results indicate that the maximum shear stress in the intersection section fluctuates relatively little under the side-guide tunnel connection scheme, without any sustained sudden increase. These results validate the rationality of using the maximum shear stress fluctuation coefficient as a stress stability evaluation index and support the technical effectiveness of side-guide tunnel path optimization in reducing local shear response fluctuations.

[0052] During construction, the outer edge of the core area of ​​the intersection, the area adjacent to the opening of the side tunnel, the area adjacent to the lower part of the process shaft, the transition area between the main tunnel sidewall and the floor slab, and the area adjacent to the intrusion of the weakened zone are the key support areas. Support can be provided using system anchor bolts, denser anchor bolts, steel mesh, shotcrete, steel plates, or a combination of steel sections. Monitoring points should be placed on the anchor bolts, steel plates, main tunnel sidewalls, side tunnel arch shoulders, the bottom of the process shaft, and adjacent to the weakened zone.

[0053] When the monitoring curve shows rapid adjustment in the early stage of construction, slow evolution in the middle and late stages, and a tendency to stabilize in the later stage, it is determined that the surrounding rock and support system at the intersection are under control. When the fluctuation coefficient of surrounding rock displacement, anchor bolt axial force, steel plate stress, support structure stress, or maximum shear stress continues to increase and exceeds the preset threshold, feedback correction is initiated, and reinforcement support measures and / or adjustments to the excavation sequence are taken. This feedback correction logic corresponds to the characteristics of dynamic correction technology.

[0054] This embodiment also provides a stability control system for the surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization, including: The parameter acquisition module is used to acquire the geological spatial parameters, surrounding rock mechanical parameters, and excavation structure parameters of the intersection section. The model building module is used to construct a three-dimensional numerical calculation model including the main tunnel, process shaft, weakened zone and reserved rock pillar to be optimized, based on the geological spatial parameters, the surrounding rock mechanical parameters and the excavation structure parameters. The working condition calculation module is used to set multiple sets of reserved rock column width working conditions according to the three-dimensional numerical calculation model, and to perform numerical calculations on each set of reserved rock column width working conditions to obtain the surrounding rock response index under each set of reserved rock column width working conditions. The index evaluation module is used to construct a comprehensive evaluation function based on the surrounding rock response index, and to use the comprehensive evaluation function to comprehensively evaluate the reserved rock column width working conditions of each group in order to determine the reserved rock column width. The path optimization module is used to retain the reserved rock pillar in the intersection section according to the width of the reserved rock pillar, and to set up side guide tunnels or auxiliary guide tunnels to change the construction path; The feedback correction module is used to acquire monitoring data during construction and dynamically correct subsequent construction parameters based on the monitoring data.

[0055] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on pre-reserved rock pillar optimization, characterized in that, Includes the following steps: Obtain the geological spatial parameters, surrounding rock mechanical parameters, and excavation structure parameters of the intersection section; Based on the geological spatial parameters, the surrounding rock mechanical parameters, and the excavation structure parameters, a three-dimensional numerical calculation model is constructed, including the main tunnel, process shaft, weakened zone, and reserved rock pillars to be optimized. Based on the three-dimensional numerical calculation model, multiple sets of reserved rock column width working conditions are set, and numerical calculations are performed on each set of reserved rock column width working conditions to obtain the surrounding rock response index under each set of reserved rock column width working conditions. Based on the surrounding rock response index, a comprehensive evaluation function is constructed, and the comprehensive evaluation function is used to comprehensively evaluate the reserved rock column width working conditions of each group in order to determine the reserved rock column width. Based on the determined reserved rock column width, reserved rock columns are retained in the intersection section, and side guide tunnels or auxiliary guide tunnels are set up to change the construction path; During construction, monitoring data is acquired, and subsequent construction parameters are dynamically corrected based on the monitoring data.

2. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 1, characterized in that, The weakened zone includes alteration zone, fracture zone, densely jointed zone, weak interlayer and combination thereof forming a low-strength surrounding rock area; The geological spatial parameters include the spatial relationship between the weakened zone and the main cavern, the spatial relationship between the weakened zone and the process shaft, the spatial relationship between the weakened zone and the connecting cavern, the width of the weakened zone, the orientation of the weakened zone, the dip angle of the weakened zone, the distance from the boundary of the weakened zone to the outline of the main cavern, and the local surrounding rock grade of the intersection section.

3. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 1, characterized in that, The surrounding rock mechanical parameters include density, bulk modulus, shear modulus, cohesion, internal friction angle, and tensile strength; the three-dimensional numerical calculation model adopts an elastoplastic constitutive model and divides the surrounding rock into a general surrounding rock zone and a weakened zone.

4. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 3, characterized in that, The equivalent elastic modulus and Poisson's ratio are calculated based on the bulk modulus and the shear modulus, and the degree of reduction in deformation parameters of the weakened zone relative to the general surrounding rock zone is determined based on the equivalent elastic modulus and the Poisson's ratio.

5. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 3, characterized in that, Based on the Mohr-Coulomb strength criterion, the shear strength of the general surrounding rock zone and the weakened zone is calculated according to the cohesion, normal stress and internal friction angle, and the degree of strength reduction of the weakened zone relative to the general surrounding rock zone is determined according to the shear strength.

6. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 1, characterized in that, The surrounding rock response index includes the displacement control rate, which is the difference between the maximum displacement of the surrounding rock under the condition of no reserved rock pillar and the maximum displacement of the surrounding rock under the condition of current reserved rock pillar width, divided by the maximum displacement of the surrounding rock under the condition of no reserved rock pillar, and then multiplied by 100%.

7. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 1, characterized in that, The surrounding rock response index includes the plastic zone control coefficient, which is the difference between the area or volume of the plastic zone under the condition of no reserved rock pillar and the area or volume of the plastic zone under the condition of current reserved rock pillar width, divided by the area or volume of the plastic zone under the condition of no reserved rock pillar, and then multiplied by 100%.

8. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 1, characterized in that, The surrounding rock response index includes the maximum shear stress fluctuation coefficient, which is the difference between the maximum shear stress peak value and the minimum shear stress peak value, divided by the average value of the maximum shear stress, and then multiplied by 100%.

9. The method for controlling the stability of surrounding rock at the intersection of an underground water-sealed cavern based on reserved rock pillar optimization according to claim 1, characterized in that, The comprehensive evaluation function is constructed based on displacement normalized evaluation values, plastic zone normalized evaluation values, volumetric stress or stress stability normalized evaluation values, maximum shear stress normalized evaluation values, and construction adaptability evaluation values. Each of the evaluation values ​​is obtained by performing range normalization processing on the corresponding original surrounding rock response indicators under the reserved rock column width conditions of each group. The value of the comprehensive evaluation function is the sum of the products of each evaluation value and its corresponding preset weight coefficient, and the sum of each preset weight coefficient is 1.

10. A stability control system for surrounding rock at the intersection of an underground water-sealed cavern based on pre-reserved rock pillars, characterized in that, include: The parameter acquisition module is used to acquire the geological spatial parameters, surrounding rock mechanical parameters, and excavation structure parameters of the intersection section. The model building module is used to construct a three-dimensional numerical calculation model including the main tunnel, process shaft, weakened zone and reserved rock pillar to be optimized, based on the geological spatial parameters, the surrounding rock mechanical parameters and the excavation structure parameters. The working condition calculation module is used to set multiple sets of reserved rock column width working conditions according to the three-dimensional numerical calculation model, and to perform numerical calculations on each set of reserved rock column width working conditions to obtain the surrounding rock response index under each set of reserved rock column width working conditions. The index evaluation module is used to construct a comprehensive evaluation function based on the surrounding rock response index, and to use the comprehensive evaluation function to comprehensively evaluate the reserved rock column width working conditions of each group in order to determine the reserved rock column width. The path optimization module is used to retain the reserved rock pillar in the intersection section according to the width of the reserved rock pillar, and to set up side guide tunnels or auxiliary guide tunnels to change the construction path; The feedback correction module is used to acquire monitoring data during construction and dynamically correct subsequent construction parameters based on the monitoring data.

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