A method and system for excavating and supporting a severely squeezed and deformed section of a soft rock tunnel

Abstract

The application discloses a soft rock tunnel serious extrusion deformation tunnel section excavation supporting method and system, relates to the underground chamber excavation supporting construction technical field; the method comprises the following steps: obtaining the surrounding rock state, determining the bench length and the reserved deformation according to the surrounding rock state; the reserved deformation is used for restraining the surrounding rock deformation and blocking the groundwater permeation; the top arch advanced support system is constructed, the large pipe shed and the small guide pipe are installed around the tunnel top arch before excavation, and the advanced consolidation grouting is carried out; the excavation supporting operation space is determined according to the bench length, after the tunnel is excavated according to the bench short footage, the rigid support construction is carried out; the H-shaped steel support is erected on the top arch, the side wall and the bottom plate after the tunnel is excavated, and the lock foot anchor rod is installed; after the lock foot anchor rod is completed, the initial support reinforcement is carried out; when the initial support is completed and the surrounding rock deformation tends to the preset deformation rate threshold value, the tunnel surrounding rock is deepened, the system drainage hole is arranged and the radial consolidation grouting is carried out. The application makes the initial support and the surrounding rock deformation coordinated, and improves the safety of the tunnel construction.

Description

Technical Field

[0001] This invention relates to the field of underground cavern excavation and support construction technology, and in particular to a method and system for excavating and supporting severely compressed and deformed sections of soft rock tunnels. Background Technology

[0002] Rapid urbanization and infrastructure development have led to a surge in demand for underground space, resulting in a continuous expansion of tunnel construction. However, many projects face adverse geological conditions, particularly weak surrounding rock, posing significant challenges to construction. When tunnels traverse weak surrounding rock, construction disturbances often trigger substantial deformation disasters, severely jeopardizing the stability and safety of the tunnel structure. To address the challenge of deformation control in tunnels with weak surrounding rock and ensure construction safety and project quality, relevant research and engineering practice have developed various combined control technologies and construction strategies, including the application of lining structures and surrounding rock reinforcement. These methods have achieved practical results in controlling deformation and improving tunnel stability and safety, but shortcomings remain that require further research and improvement.

[0003] Prior art 1, Chinese patent, patent number: 202510808514.8, relates to the field of tunnel excavation construction technology, and discloses a method and system for excavation and support construction of a tunnel section with roof collapse in strongly altered rock mass. The method includes: supporting the rock walls of the tunnel section at a distance of A meters from both sides of the strongly altered rock mass with a combined support structure composed of steel arch frames and system anchor bolts; after the combined support structure is completed, installing a large pipe roof above the combined support structure, inclined along the tunnel length direction and penetrating the strongly altered rock mass according to a set rule; after the large pipe roof is installed, excavating the strongly altered rock mass, and supporting the excavated areas during the excavation process, until the entire tunnel section with roof collapse is excavated and supported. Although detailed support parameters for the tunnel section with strongly altered rock mass and the intact rock mass within the Am range on both sides are proposed, and the support parameters can be used to effectively support the above-mentioned tunnel section, there are problems such as a lag in the connection between excavation and support, and insufficient stability of rigid support, leading to instantaneous compression deformation and collapse after the soft rock is excavated.

[0004] Prior art two, Chinese patent, patent number: 202410833169.9, discloses a combined advanced support construction method for shallow buried sections of tunnels with adverse geological conditions. The combined advanced support construction method for shallow buried sections of tunnels with adverse geological conditions includes the following steps: excavating the open section of the tunnel, pouring arch concrete and constructing advanced large pipe roofs; after the advanced large pipe roof grouting is completed and a preset curing time is allowed, surface grouting is carried out; the shallow buried section tunnel body is excavated and supported, using the ring-shaped pilot tunnel with reserved core soil method for excavation; a 5m long overlap section is set at the end of the large pipe roof, and advanced support construction combining advanced small guide pipes and advanced anchor bolts is carried out from the starting point of the long overlap section; the advanced support construction steps combining advanced small guide pipes and advanced anchor bolts are repeated until the tunnel passes through the shallow buried section with adverse geological conditions. Although the proposed combined advanced support construction method for shallow buried sections of tunnels with adverse geological conditions has the advantages of safe and fast construction and small over-excavation in such sections, it also has the problems of relying on experience to set the step length and allow for deformation, which can easily lead to insufficient deformation space causing the support structure to collapse, or excessive space causing waste of resources.

[0005] Existing technology three, Chinese patent, patent number: 202511133670.5, discloses a construction method for the excavation and support molding of a tunnel with a full-section invert arch, including the following steps: construction preparation; fabrication of an arch frame, the arch frame including an arch wall section and an invert arch section, assembling and connecting the arch wall section and the invert arch section; drilling holes at the tunnel face to obtain blasting holes, installing detonators in the blasting holes, and blasting to obtain the tunnel cross-section; trimming the outline of the tunnel cross-section; installing the arch frame onto the tunnel cross-section, connecting and hanging steel mesh on the arch frame; wet spraying concrete on the invert arch section and arch wall section to form a closed support ring; monitoring and measuring the tunnel cross-section. Although existing technologies for constructing inverted arches often require separate operations after the arch wall is closed, resulting in long opening times, high construction difficulty, and a structure where the arch wall is closed but the inverted arch is not, leading to incomplete circumferential stress and poor overall stability; however, there are still problems with advanced support often using only a single pipe roof or small pipe, and the grouting and drainage are disconnected, making it difficult to simultaneously block groundwater and restrain deformation.

[0006] Currently, existing technologies 1, 2, and 3 suffer from problems such as blind parameter calibration, simplistic advanced support methods, incomplete water hazard control, and uncontrolled instantaneous deformation after excavation. To address these issues, this invention provides a method for excavating and supporting severely compressed and deformed sections of soft rock tunnels. Summary of the Invention

[0007] The main objective of this invention is to provide a method and system for excavating and supporting severely compressed and deformed sections of soft rock tunnels, in order to solve the problems of blind parameter calibration, simplistic advanced support, incomplete water hazard prevention and control, and uncontrolled instantaneous deformation after excavation in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for excavating and supporting severely compressed and deformed sections of soft rock tunnels, comprising the following steps: The excavation and support work space is determined according to the step length. After the tunnel is excavated in short advances in steps, rigid support construction is carried out to limit the displacement of the surrounding rock surface. After the tunnel is excavated, H-beam supports are erected for the top arch, side walls and bottom plate, and anchor bolts are installed. After the anchor bolts are installed, initial support reinforcement is carried out; after the tunnel is excavated, the inner wall of the tunnel is sprayed with concrete, double-layer steel mesh is hung, and clearance anchor bolts are installed; when the initial support is completed and the deformation of the surrounding rock tends to the preset rate threshold, the drainage holes of the tunnel surrounding rock deepening system are filled and radial consolidation grouting is carried out.

[0009] As a further improvement of the present invention, the process of determining the excavation and support working space based on the step length includes the following steps: Based on the stable excavation step distance, the longitudinal disturbance range of the tunnel face is deduced, which describes the significant stress adjustment of the longitudinal depth of the unexcavated rock mass caused by the excavation activities. The longitudinal disturbance range of the tunnel face is combined with the designed excavation profile of the tunnel to define the initial working envelope. The initial working envelope represents the theoretical space volume required for all large mechanical equipment to perform core operations in a single cycle of excavation. Using the minimum compression amount as the quantitative basis for boundary shrinkage, uniform radial displacement reduction is carried out from the inner side of the top arch, sidewall and bottom plate of the initial working envelope to generate a working space after convergence compensation that takes into account the inevitable convergence of the surrounding rock. Based on the convergence compensation working space and the installation process requirements of the support structure, the interference-free installation domain of the rigid support is clearly defined.

[0010] As a further improvement of the present invention, the process of defining the initial working envelope includes the following steps: The stable excavation step distance is used as the mechanical excitation scale for a single advance of the face. The mechanical excitation scale is combined with the structural looseness index. The structural looseness index is converted into a stress wave transmission attenuation coefficient to quantify the agility and persistence of excavation disturbance in a specific rock mass medium. The stress wave transmission attenuation coefficient is used to perform a transmission correction on the mechanical excitation scale and calculate the stress redistribution front depth. The stress redistribution front depth is used as a dynamic boundary and spatially superimposed with the static geometric boundary of the tunnel design excavation profile. The design excavation profile is stretched along the tunnel axis and extended in front of the tunnel face. The length of the extension is the stress redistribution front depth, thus constructing an excavation influence prism in three-dimensional space. An operational adaptation transformation is carried out on the excavation-affected prism. Taking into account the minimum turning radius, working arm range, and safe distance of large machinery and equipment and their collaborative operations, a free operating domain for the equipment without internal structural interference is defined inside the excavation-affected prism. The free operating domain for the equipment is the defined initial operating envelope.

[0011] As a further improvement of the present invention, the process of calculating the depth of the stress redistribution front includes the following steps: The mechanical excitation scale is coupled with the stress wave propagation attenuation coefficient. The mechanical excitation scale is used as the input and substituted into the nonlinear attenuation function that characterizes the energy absorption characteristics of the rock mass. The shape of the nonlinear attenuation function is uniquely determined by the stress wave propagation attenuation coefficient. Through the calculation of the nonlinear attenuation function, an uncorrected disturbance propagation distance is output. The uncorrected disturbance propagation distance is compared and calibrated with the critical disturbance intensity threshold. Through iterative feedback, the longitudinal distance corresponding to the decrease of the disturbance intensity to the critical disturbance intensity threshold under the action of the nonlinear decay function is found. The critical disturbance intensity threshold is derived from the definition of the critical energy density required for irreversible adjustment of the rock mass microstructure. It is a constant parameter derived from the constitutive properties of the rock mass. The longitudinal distance, after calibration with the critical disturbance intensity threshold, is confirmed as the depth of the stress redistribution front; that is, the longitudinal disturbance range of the working face, indicating the farthest longitudinal boundary that can be affected by the mechanically significant stress adjustment triggered by this excavation.

[0012] As a further improvement of the present invention, the process of determining the longitudinal distance corresponding to the decay of the disturbance intensity to the critical disturbance intensity threshold includes the following steps: The uncorrected perturbation propagation distance is redefined as the initial estimated propagation limit, located on a perturbation intensity decay curve described by a nonlinear decay function; meanwhile, the critical perturbation intensity threshold is regarded as a threshold horizontal line parallel to the distance axis. Starting with the initial estimated propagation limit, the perturbation intensity value corresponding to the starting point on the perturbation intensity decay curve is calculated; the perturbation intensity value is compared with the critical perturbation intensity threshold for the first time, and the difference is quantified as the primary intensity surplus; Based on the direction and magnitude of the primary strength surplus, a distance-strength feedback loop is initiated. If a primary strength surplus exists, it indicates that the disturbance strength is still higher than the critical threshold at the current estimated distance, and it is necessary to search for the intersection point along the decay curve in the direction of increasing distance. Conversely, it searches in the direction of decreasing distance. The feedback loop adjusts the assumed longitudinal distance value and repeatedly substitutes it into the nonlinear decay function to calculate the corresponding disturbance strength until a certain longitudinal distance is found that makes the difference between the calculated disturbance strength and the critical disturbance strength threshold less than a preset tolerance.

[0013] As a further improvement of the present invention, the process of calculating the disturbance intensity value corresponding to the starting point on the disturbance intensity decay curve includes the following steps: The initial estimated propagation limit is multiplied by the reciprocal of the stress wave propagation attenuation coefficient to generate an intermediate parameter, called the reference energy level. Multiplying the reference energy level by the intensity correction factor yields the unnormalized initial intensity value; the intensity correction factor serves as the mechanical excitation scale of the input parameter, and its specific value is inversely proportional to the square root of the mechanical excitation scale. The initial intensity value is compared with the normalized reference value used when calculating the uncorrected disturbance propagation distance through a nonlinear decay function. The ratio is taken and multiplied by the system's preset reference intensity constant to finally obtain the standardized disturbance intensity value.

[0014] As a further improvement of the present invention, the process of comparing the initial intensity value with the normalized reference value used when calculating the uncorrected disturbance propagation distance through a nonlinear attenuation function includes the following steps: The initial intensity value is proportional to the normalized reference value. The initial intensity value is used as the dividend and the normalized reference value is used as the divisor. The ratio between the two is calculated to form a dimensionless scaling factor. The scaling factor reflects the relative magnitude of the intensity level of the current estimated point relative to the system calculation reference. The scaling factor is multiplied by the system's preset reference strength constant. The reference strength constant is a fixed parameter with strength dimensions. Its function is to give the obtained dimensionless scaling factor a new physical meaning and dimension of strength in actual engineering. The scaling factor is converted into an intensity value with a clear physical meaning and dimensions; the final value after conversion is the standardized disturbance intensity value.

[0015] As a further improvement of the present invention, the process of setting the preset variable rate threshold includes the following steps: The structural looseness index is mapped to characterize the rheological properties of the rock mass, and a parameter directly related to the time-dependent deformation capacity of the rock mass is output, called the deformation sensitivity coefficient. The deformation sensitivity coefficient is used to decompose the minimum compression amount on a time scale, and the minimum compression amount is taken as the total deformation. Combined with the reasonable stable period determined in the engineering construction plan, the upper limit of the deformation amount per unit time under the premise of ensuring that the minimum compression amount is not exceeded is obtained, i.e., the critical compression rate. By introducing a stable excavation step distance as a spatial constraint, the critical compression rate and the stable excavation step distance are coupled and analyzed to analyze their mutual constraints in the spatiotemporal dimensions. The allowable deformation rate benchmark value that matches the spatial advance during the implementation of a single excavation step distance is derived, i.e., the initial deformation rate threshold. Based on the enhanced deformation control capability of the support structure, the initial variable rate threshold is modified; according to the additional constraint stiffness provided by the support system, the value of the initial variable rate threshold is increased to form the final preset variable rate threshold for engineering monitoring.

[0016] As a further improvement of the present invention, it also includes obtaining the surrounding rock condition, determining the step length and reserved deformation amount based on the surrounding rock condition; constraining the surrounding rock deformation and blocking groundwater seepage based on the reserved deformation amount; constructing a top arch advanced support system, installing large pipe sheds and small pipes around the tunnel top arch before excavation, and carrying out advanced consolidation grouting.

[0017] To achieve the above objectives, the present invention also provides the following technical solution: A support system for excavating severely deformed sections of soft rock tunnels is disclosed, which is applied to the aforementioned method for excavating and supporting severely deformed sections of soft rock tunnels. The support system for excavating severely deformed sections of soft rock tunnels includes: an initial support system, reserved core soil, upper bench, middle bench, lower bench, advanced small guide pipes, advanced large pipe roof, radial consolidation grouting, clearance anchor bolts, drainage holes of the side-top arch deepening system, advanced support system, advanced consolidation grouting, reserved deformation amount, steel support, thin steel plate, locking large pipe roof, welded parts, locking connecting bars, and locking anchor bolts. The initial support system is divided into upper, middle, and lower steps; the upper step has reserved core soil; advanced small guide pipes are connected to the outside of the initial support system, and advanced large pipe sheds are also provided; several radial consolidation grouting, clearance anchors, and drainage holes of the side-top arch deepening system are connected to the initial support system; a reserved deformation amount is set outside the initial support system; an advanced support system is set outside the reserved deformation amount; and several advanced consolidation grouting is set inside the initial support system. Install H-beam supports. Weld a thin steel plate between the two steel supports of the top arch and the side wall, and use a locking foot pipe to connect the steel support and the thin steel plate. Install two locking foot anchors at the joint and the arch foot, and weld the locking foot connecting bar, locking foot anchor and H-beam supports. Hang double-layer steel mesh on the inner wall of the tunnel and spray C20 coarse fiber concrete, and install clearance anchors. After the initial support is completed, deepen the drainage holes of the side arch and apply radial consolidation grouting.

[0018] This invention employs pre-consolidation grouting with large pipe roofs and small guide pipes, followed by radial consolidation grouting after the initial support is completed. This effectively improves the strength and integrity of the surrounding rock around the tunnel. By spraying coarse fiber concrete onto the top arch and using large pipe roofs as steel supports to form a combined support structure, the overall strength and stability of the initial support are further improved. By reserving a certain amount of deformation during excavation, a buffer space is provided for the deformation of the surrounding rock, ensuring that the initial support is coordinated with the deformation of the surrounding rock and improving the safety of tunnel construction. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart illustrating the steps of an embodiment of the method for excavating and supporting severely compressed and deformed sections of soft rock tunnels according to the present invention. Figure 2 This is a schematic diagram illustrating the steps of determining the step length and reserved deformation amount based on the surrounding rock condition in an embodiment of the method for excavating and supporting severely squeezed and deformed sections of soft rock tunnels according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the steps for determining the excavation and support working space based on the step length in an embodiment of the method for excavation and support of severely squeezed and deformed soft rock tunnels according to an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the steps of setting a preset variable rate threshold in an embodiment of the excavation and support method for severely squeezed and deformed soft rock tunnels according to the present invention. Figure 5 This is a schematic diagram of the structure of a soft rock tunnel after the second and third steps are opened in the cross section of a soft rock tunnel, according to an embodiment of the excavation and support system for a severely compressed and deformed section of a soft rock tunnel of the present invention. Figure 6 This is an embodiment of the excavation and support system for severely compressed and deformed sections of soft rock tunnels according to the present invention. It is a cross-sectional view of the advance support and initial support layout of a soft rock tunnel. Figure 7 This is an embodiment of the excavation and support system for severely compressed and deformed sections of soft rock tunnels according to the present invention. It is a longitudinal section diagram of the large pipe roof and small pipe arrangement of a soft rock tunnel. Figure 8 This is a longitudinal view of a lock-toe pipe roof, representing an embodiment of the excavation and support system for severely compressed and deformed soft rock tunnels according to the present invention. Figure 9 This is a detailed drawing of the anchor bolt and connection of an embodiment of the excavation support system for severely compressed and deformed soft rock tunnel sections according to the present invention; Figure 10 This is a schematic diagram of the structure of an embodiment of the electronic device of the present invention; Figure 11 This is a schematic diagram of the structure of one embodiment of the storage medium of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] The terms "first," "second," and "third" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of those features. In the description of this invention, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this invention are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indication changes accordingly. Furthermore, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0022] References to embodiments herein mean that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] like Figure 1 As shown, this embodiment provides an example of a method for excavating and supporting severely deformed sections of soft rock tunnels. Specifically, this method includes the following steps: Step S1: Obtain the surrounding rock condition, determine the step length and reserved deformation amount based on the surrounding rock condition; constrain the surrounding rock deformation and block groundwater seepage based on the reserved deformation amount; construct the arch support system, install large pipe sheds and small pipes around the tunnel arch before excavation, and carry out advance consolidation grouting. Step S2: Determine the excavation and support work space according to the step length. After the tunnel is excavated in short advances in steps, carry out rigid support construction to limit the displacement of the surrounding rock surface. After the tunnel is excavated, H-beam supports are erected for the top arch, side walls and bottom plate, and anchor bolts are installed. Step S3: After the anchor bolts are installed, initial support reinforcement is carried out; after the tunnel is excavated, sprayed concrete is applied to the inner wall of the tunnel, double-layer steel mesh is installed, and clearance anchor bolts are installed; when the initial support is completed and the deformation of the surrounding rock tends to the preset rate of change threshold, the drainage holes of the tunnel surrounding rock deepening system are filled and radial consolidation grouting is carried out.

[0024] Preferably, this embodiment uses large pipe roofs and small guide pipes for pre-consolidation grouting, followed by radial consolidation grouting after the initial support is completed. This effectively improves the strength and integrity of the surrounding rock around the tunnel. By spraying coarse fiber concrete on the top arch and using large pipe roofs as steel support feet to form a combined support, the overall strength and stability of the initial support are further improved. By reserving a certain amount of deformation during excavation, a buffer space is provided for the deformation of the surrounding rock, so that the initial support is coordinated with the deformation of the surrounding rock, thus improving the safety of tunnel construction.

[0025] In summary, this embodiment, by pre-controlling the surrounding rock condition, accurately determining the step length and reserved deformation amount, and combining the top arch large pipe shed, small pipe advanced support, and consolidation grouting, constrains the tendency of soft rock compression deformation in advance, blocks the groundwater seepage path, reduces the risk of surrounding rock disturbance from the source, and lays a solid safety foundation for subsequent excavation and support. The working space is delineated according to the preset step length, and H-beam supports and anchor bolts are immediately erected after short-foot excavation to quickly construct a rigid load-bearing skeleton, effectively limiting the surface displacement of the surrounding rock and preventing collapse caused by instantaneous deformation after excavation, thus ensuring the safety of the construction process. Initial support reinforcement and closure are achieved through shotcrete, double-layer steel mesh, and clearance anchor bolts, balancing support rigidity and deformation adaptability to prevent structural damage due to compression. Once the surrounding rock deformation reaches the preset threshold, deep drainage holes and radial consolidation grouting work together to reduce pore water pressure, cement deep cracks in the surrounding rock, and significantly improve the overall strength and deformation resistance of the surrounding rock. This embodiment targets surrounding rock with severe compression deformation, employing a three-stage excavation method. The allowable deformation and stage excavation dimensions are determined based on the surrounding rock conditions. Before excavation, pre-arch small guide pipes, pre-arch large pipe sheds, and pre-arch consolidation grouting are installed around the tunnel. After each stage excavation is completed: coarse fiber reinforced concrete is sprayed onto the arch crown and sidewalls of the corresponding excavation face, double-layer steel mesh is installed, and clearance anchors are constructed. Then, steel supports are installed on the arch crown and sidewalls of the corresponding excavation face, and the system drainage holes are deepened.

[0026] Furthermore, such as Figure 2 As shown, step S1, which involves determining the step length and the allowable deformation based on the surrounding rock condition, specifically includes the following steps: Step S11: Collect frequency response spectrum data of the surrounding rock under micro-vibration environment by deploying a multi-axis vibration sensor array around the tunnel. After spectrum decomposition, obtain the inherent vibration mode characteristics of the surrounding rock. Based on the inherent vibration mode characteristics, derive the structural looseness index of the surrounding rock by calculating the energy attenuation rate of the main frequency band, which reflects the degree of development of internal cracks and weak surfaces of the rock mass. Step S12: Using the structural looseness index and the geometric parameters of the tunnel design profile, perform dynamic stability simulation; during the dynamic stability simulation, the potential deformation trajectory of the surrounding rock under unsupported conditions is obtained based on the structural looseness index, and the maximum instantaneous deformation rate and the critical point of permeability are extracted. Step S13: The maximum instantaneous deformation rate is used to determine the step length. By comparing it with the preset safety threshold, the stable excavation step distance is derived, which is the step length. The seepage critical point is used to determine the reserved deformation amount. By assessing the risk of groundwater seepage along the deformation cracks, the minimum compression amount is calculated. The minimum compression amount is used as the reserved deformation amount. The rock mass is squeezed by active deformation control to close potential seepage paths.

[0027] Preferably, this embodiment acquires the frequency response spectrum data of the surrounding rock through a multi-axis vibration sensor array, obtains the inherent vibration mode characteristics through spectral decomposition, and then calculates the structural looseness index derived from the energy attenuation rate of the main frequency band. This index can quantitatively characterize the development state of internal fractures and weak surfaces in the rock mass. Based on the structural looseness index and tunnel geometric parameters, dynamic stability simulation is carried out to deduce the potential deformation trajectory of the surrounding rock under unsupported conditions, thereby extracting two key parameters: the maximum instantaneous deformation rate and the seepage critical point. The stable excavation step distance, i.e., the bench length, is determined by comparing the maximum instantaneous deformation rate with the safety threshold; the seepage critical point is calculated by assessing the groundwater seepage risk and determining the minimum compression amount, i.e., the reserved deformation amount. This embodiment achieves quantitative evaluation and active control of surrounding rock stability: the structural looseness index accurately reflects the integrity of the rock mass structure, dynamic stability simulation predicts the deformation development trend, bench length control ensures the stability of the excavation process, and the reserved deformation amount design actively compresses the rock mass to block the seepage path, ultimately achieving the dual goals of safe excavation and seepage control.

[0028] Furthermore, the process of calculating the minimum compression amount in step S13 specifically includes the following steps: Step S131: Based on the permeability critical point, the potential permeability network configuration is derived by analyzing the expansion pattern of the crack network in the potential deformation trajectory; the potential permeability network configuration describes the geometric characteristics of the fracture system that may become a water flow channel under the condition of no intervention, which is dominated by deformation. Step S132: Quantitatively modify the potential permeable network configuration using the obtained structural looseness index; the structural looseness index is applied to the potential permeable network configuration, and by evaluating the connectivity vulnerability of its internal nodes, the crack connectivity index is obtained, which characterizes the degree of difficulty for the permeable network to lose connectivity under external pressure. Step S133: Combining the geometric parameters of the tunnel design profile, the fracture connectivity index is used to derive the critical closure strain required to cause the failure of the dominant seepage path by simulating the closure effect of the seepage network under different degrees of compression. The critical closure strain is converted into the radial displacement of the tunnel profile according to the constitutive relationship of the rock mass, and amplified by a preset safety margin coefficient based on engineering experience to obtain the minimum compression amount that ensures the seepage path is effectively compressed and blocked. The minimum compression amount is used as the reserved deformation amount. Its purpose is to actively promote the potential seepage network inside the rock mass to complete self-compression before the support system plays its role through the pre-set and controlled surrounding rock convergence, thereby fundamentally blocking the development channel of groundwater seepage.

[0029] Preferably, this embodiment analyzes the crack propagation pattern in the potential deformation trajectory based on the critical point of permeability, constructs a potential permeability network configuration, and fully describes the spatial distribution characteristics of the fracture system that may form water flow channels; the permeability network configuration is quantitatively corrected using the structural looseness index, and the fracture connectivity index is obtained by evaluating the vulnerability of network node connectivity. This index objectively reflects the sensitivity of the permeability network to losing connectivity under external pressure; combined with tunnel geometric parameters, the fracture connectivity index is input into the closure effect simulation system to deduce the critical closure strain required to cause the failure of the dominant permeability path; the critical closure strain is converted into the radial displacement of the tunnel through the rock mass constitutive relation, and the engineering safety margin coefficient is introduced for necessary amplification, finally determining the minimum compression amount to ensure the complete closure of the permeability path.

[0030] In summary, this embodiment forms a complete seepage control mechanism: the potential seepage network configuration accurately identifies the development pattern of water flow channels, the fracture connectivity index quantitatively assesses the stability of the network structure, the critical closure strain calculation provides the theoretical closure threshold, and the safety margin coefficient ensures the reliability of the project; it realizes a complete technical path from seepage risk identification to control parameter determination, and promotes the autonomous compression of seepage channels by preset radial displacement, eliminating seepage risks in advance before the support system takes effect, forming an active waterproof barrier; it transforms traditional passive waterproofing into active control based on rock mass mechanical behavior, effectively improving the long-term waterproof reliability of tunnel engineering.

[0031] Furthermore, such as Figure 3 As shown, step S2, which involves determining the excavation and support working space based on the step length, specifically includes the following steps: Step S21: Based on the stable excavation step distance, deduce the longitudinal disturbance range of the tunnel face that describes the significant stress adjustment of the longitudinal depth of the unexcavated rock mass caused by the excavation activities; combine the longitudinal disturbance range of the tunnel face with the designed excavation profile of the tunnel to delineate the initial working envelope; the initial working envelope represents the theoretical space volume required for all large mechanical equipment (such as tunneling machines and loading equipment) to perform core operations in a single cycle of excavation; Step S22: Using the minimum compression amount as the quantitative basis for boundary shrinkage, uniform radial displacement reduction is carried out from the inner side of the top arch, sidewall and bottom plate of the initial working envelope to generate a convergence compensation working space that takes into account the inevitable convergence of the surrounding rock. Step S23: Based on the convergence compensation working space and the installation process requirements of the support structure, clearly define the interference-free installation domain of the rigid support.

[0032] Preferably, in this embodiment, the longitudinal disturbance range of the tunnel face is deduced based on the stable excavation step distance, and the initial working envelope is delineated in conjunction with the tunnel design outline to accurately define the theoretical working space of large mechanical equipment in single-cycle excavation; the radial displacement of the initial working envelope is reduced based on the minimum compression amount to generate the working space after convergence compensation, which has fully considered the compression effect of surrounding rock convergence on the actual working space; finally, in conjunction with the installation process requirements of the support structure, the non-interference installation domain of rigid support is clearly defined within the working space after convergence compensation.

[0033] The initial working envelope of this embodiment ensures the basic space requirements for equipment operation, the convergence compensation mechanism eliminates the encroachment of surrounding rock deformation on the working space in advance, and the non-interference installation domain ensures the coordination between the support structure and the working space; it realizes the dynamic adaptation between excavation and support operations and surrounding rock deformation, which not only meets the equipment operating space requirements, but also takes into account the surrounding rock convergence characteristics and support installation accuracy, effectively improving construction safety and operation efficiency.

[0034] Furthermore, the process of defining the initial job envelope in step S21 specifically includes the following steps: Step S211: The stable excavation step distance is used as the mechanical excitation scale for a single free face advance at the tunnel face. The mechanical excitation scale is combined with the structural looseness index. The structural looseness index is converted into a stress wave conduction attenuation coefficient to quantify the agility and persistence of excavation disturbance in a specific rock mass medium. Using the stress wave conduction attenuation coefficient, the mechanical excitation scale is corrected for conductivity, the stress redistribution front depth is calculated, and the farthest longitudinal distance that the stress change triggered by this excavation behavior can reach, which is sufficient to cause irreversible adjustment of the rock mass microstructure, is defined as the longitudinal disturbance range of the tunnel face. Step S212: The stress redistribution front depth is used as a dynamic boundary and spatially superimposed with the static geometric boundary of the tunnel design excavation profile. The design excavation profile is stretched along the tunnel axis and extended in front of the tunnel face. The length of the extension is the stress redistribution front depth. An excavation influence prism is constructed in three-dimensional space. Step S213: Adapt the excavation impact prism to operational needs. Taking into account the minimum turning radius, boom extension range, and safe distance for coordinated operations of large machinery, define a free operating domain for the equipment within the excavation impact prism without interference from internal structures. The free operating domain is the defined initial operating envelope, ensuring that all mechanical functions can be safely and fully utilized within the stable construction zone defined by the stress field migration boundary.

[0035] Preferably, in this embodiment, the depth of the stress redistribution front is accurately calculated by using the stable excavation step distance as the mechanical excitation scale and combining it with the stress wave transmission attenuation coefficient transformed from the structural looseness index, thereby scientifically defining the longitudinal disturbance range of the tunnel face; the dynamic boundary is superimposed with the tunnel design outline to construct the excavation influence prism, which fully characterizes the three-dimensional rock mass response area caused by the excavation behavior; on this basis, an operational adaptation transformation is carried out, and by integrating equipment motion parameters and safety distance requirements, the free operating domain of the equipment is precisely defined within the influence prism to form the initial operating envelope.

[0036] This embodiment achieves an organic integration of rock mass mechanical response and construction space: the depth of the stress redistribution front quantifies the boundary of excavation disturbance propagation, the excavation influence prism constructs the construction safety control domain, and the equipment free operation domain ensures the integrity and safety of mechanized operations. By systematically integrating rock mass stress state, spatial geometric constraints, and equipment operating characteristics, a standard for delineating the work space based on mechanical mechanisms is formed, providing a theoretical foundation and engineering guidance for efficient and safe tunnel construction.

[0037] Furthermore, the process of calculating the depth of the stress redistribution front in step S211 specifically includes the following steps: Step S2111: Couple the mechanical excitation scale with the stress wave propagation attenuation coefficient. The mechanical excitation scale is used as input and substituted into the nonlinear attenuation function characterizing the energy absorption properties of the rock mass. The shape of the nonlinear attenuation function is uniquely determined by the stress wave propagation attenuation coefficient. Through the calculation of the nonlinear attenuation function, an uncorrected disturbance propagation distance is output. The nonlinear attenuation function is used to accurately predict the propagation limit of excavation disturbance in the surrounding rock, and its expression is:

[0038] This function is based on the physical principle that energy dissipates nonlinearly with distance. It simulates how the energy or intensity of stress waves generated during excavation does not simply decay linearly when traversing soft rock masses with complex fracture networks, but rather follows a decay pattern that is initially rapid and then slows down. The exponential term in the function... A distance-dependent attenuation factor is introduced, with the core insight that: during propagation, disturbances not only attenuate due to the inherent properties of the rock mass (determined by β), but the degree of attenuation itself intensifies with increasing propagation distance D; thus increasing the propagation distance of the disturbance. The final calculation results can more realistically reflect the strong energy absorption and scattering effects of soft rock media. The main function of this function is to act as a mathematical simulator of a physical process, mapping the theoretically possible maximum disturbance range (uncorrected disturbance propagation distance D) to a corrected estimated distance that is more in line with engineering physics reality through a nonlinear transformation strictly constrained by the inherent properties of the rock mass (stress wave propagation attenuation coefficient β). The output result is a benchmark value that is compared and calibrated with the critical disturbance intensity threshold, and it is the logical starting point and key input for the entire determination of the stress redistribution front depth.

[0039] represents the uncorrected disturbance propagation distance, the output value of the function, usually in meters (m). It represents an intermediate calculation result after considering nonlinear attenuation but before final comparison with the engineering critical value; D represents the mechanical excitation scale, the input value of the function, usually in meters (m), directly derived from the determined stable excavation step distance (i.e., step length), quantifying the initial intensity or scale of the disturbance to the surrounding rock in space caused by this excavation operation; β represents the stress wave propagation attenuation coefficient, a dimensionless coefficient, a key parameter of the function, derived from the derived structural looseness index, which reflects the degree of development of internal fractures and weak surfaces in the rock mass; the higher the structural looseness index, the larger the value of β, meaning the more fragmented the rock mass, the worse its ability to propagate stress waves, and the faster the attenuation; exp(): represents the natural exponential function, a mathematical tool for constructing nonlinear attenuation relationships; this nonlinear attenuation function, by organically combining the two key parameters of mechanical excitation scale and stress wave propagation attenuation coefficient, realizes the quantitative simulation of the surrounding rock disturbance propagation behavior, providing a crucial theoretical basis for accurately defining the safe excavation and support operation space; Step S2112: Compare and calibrate the uncorrected disturbance propagation distance with the critical disturbance intensity threshold. Through iterative feedback, find the longitudinal distance corresponding to the disturbance intensity decaying to the critical disturbance intensity threshold under the action of the nonlinear decay function. The critical disturbance intensity threshold is derived from the definition of the critical energy density required for irreversible adjustment of the rock mass microstructure. It is a constant parameter derived from the constitutive properties of the rock mass. Step S2113: The longitudinal distance calibrated after the critical disturbance intensity threshold is confirmed as the stress redistribution front depth; that is, the longitudinal disturbance range of the working face, indicating the farthest longitudinal boundary that can be affected by the mechanically significant stress adjustment triggered by this excavation.

[0040] Preferably, this embodiment couples the mechanical excitation scale with the stress wave propagation attenuation coefficient. The uncorrected disturbance propagation distance is calculated using a nonlinear attenuation function, accurately reflecting the nonlinear absorption characteristics of the rock mass for energy propagation. The uncorrected disturbance propagation distance is compared and calibrated with a critical disturbance intensity threshold. Iterative feedback determines the longitudinal distance at which the disturbance intensity attenuates to the critical threshold, ensuring that the calculation results conform to the energy conditions for irreversible structural adjustment of the rock mass. The depth of the stress redistribution front is confirmed by the calibrated longitudinal distance, accurately defining the longitudinal impact range of stress adjustment triggered by excavation at the working face. This achieves quantitative determination of the excavation disturbance range of the rock mass, providing a reliable theoretical basis for engineering stability control.

[0041] In summary, this embodiment obtains the uncorrected disturbance propagation distance by coupling the stress wave propagation attenuation coefficient with the mechanical excitation scale, and then accurately defines the stress redistribution front depth by calibrating the critical disturbance intensity threshold. This ensures that the calculated front depth not only reflects the physical process of disturbance propagation, but more importantly, it incorporates the mechanical criteria for irreversible rock mass response, making it a reliable dynamic boundary for delineating the working space.

[0042] Furthermore, the process of determining the longitudinal distance corresponding to the decay of the disturbance intensity to the critical disturbance intensity threshold in step S2112 specifically includes the following steps: Step S21121: The uncorrected disturbance propagation distance is redefined as the initial estimated propagation limit, located on a disturbance intensity decay curve described by a nonlinear decay function; at the same time, the critical disturbance intensity threshold is regarded as a threshold horizontal line parallel to the distance axis. Step S21122: Starting from the initial estimated propagation limit, calculate the disturbance intensity value on the disturbance intensity decay curve corresponding to the starting point; make an initial comparison between the disturbance intensity value and the critical disturbance intensity threshold, and quantify the difference as the primary intensity surplus; Step S21123: Based on the direction and magnitude of the primary strength surplus, initiate the distance-strength feedback loop; if a primary strength surplus exists, it indicates that the disturbance strength is still higher than the critical threshold at the current estimated distance, and it is necessary to search for the intersection point along the attenuation curve in the direction of increasing distance; otherwise, search in the direction of decreasing distance; the feedback loop adjusts the assumed longitudinal distance value and repeatedly substitutes it into the nonlinear attenuation function to calculate the corresponding disturbance strength until a certain longitudinal distance is found that makes the difference between the calculated disturbance strength and the critical disturbance strength threshold less than a preset tolerance; the longitudinal distance that meets the tolerance condition is confirmed as the calibration distance, which is the depth of the stress redistribution front.

[0043] Preferably, this embodiment constructs a systematic intersection point localization method by setting the uncorrected disturbance propagation distance as the initial estimated propagation limit and forming a curve-horizontal line geometric relationship with the critical disturbance intensity threshold. A primary intensity surplus is generated by calculating the difference between the disturbance intensity at the initial point and the critical threshold, providing a directional basis for the search. Based on the distance-intensity feedback loop initiated by the intensity surplus direction, a method of dynamically adjusting the longitudinal distance and iteratively calculating is used to achieve precise intersection point localization between the nonlinear decay function and the threshold horizontal line. Finally, the calculation accuracy is controlled by a preset tolerance to obtain a calibration distance that meets the accuracy requirements. This achieves automatic calibration of the disturbance propagation distance, establishes a criterion for determining the depth of the stress redistribution front, and improves the accuracy and computational efficiency of critical state identification.

[0044] This embodiment derives the primary strength surplus from the initial estimated propagation limit and critical disturbance strength threshold, and then determines the calibration distance through a distance-strength feedback loop; it ensures the determination of the stress redistribution front depth, strictly follows the mathematical correspondence between physical attenuation laws and engineering critical states, and achieves a deep integration of theoretical calculations and engineering safety criteria.

[0045] Furthermore, the process of calculating the disturbance intensity value corresponding to the starting point on the disturbance intensity attenuation curve in step S21122 specifically includes the following steps: Step S211221: Couple the initial estimated propagation limit with the stress wave propagation attenuation coefficient, and multiply the value of the initial estimated propagation limit with the reciprocal of the stress wave propagation attenuation coefficient to generate an intermediate parameter, called the reference energy level. Step S211222: Multiply the reference energy level by the intensity correction factor to obtain the unnormalized initial intensity value; the intensity correction factor is used as the mechanical excitation scale of the input parameter, and its specific value is inversely proportional to the square root of the mechanical excitation scale; Step S211223: Compare the initial intensity value with the normalized reference value used when calculating the uncorrected disturbance propagation distance through the nonlinear attenuation function, take the ratio and multiply it by the system's preset reference intensity constant to finally obtain the standardized disturbance intensity value.

[0046] Preferably, in this embodiment, a reference energy level is generated by coupling the initial estimated propagation limit with the stress wave propagation attenuation coefficient, thus achieving a match between the propagation limit and the medium attenuation characteristics. After multiplying the reference energy level by the intensity correction factor, a correlation is established between the mechanical excitation scale and the initial intensity value, reflecting the influence of actual excitation conditions on the intensity calculation. By comparing the initial intensity value with the normalized reference value and multiplying it by a reference intensity constant, the standardization of the disturbance intensity value is completed, eliminating systematic bias and ensuring that the calculation results meet the requirements of a unified dimension. The entire process realizes the transformation from theoretical parameters to actual intensity values, ensuring the accuracy and comparability of the disturbance intensity calculation. The standardized intensity value obtained after the above steps is the disturbance intensity at the current estimated point, which accurately characterizes the disturbance energy level at the initially estimated propagation limit location. The entire process forms a deterministic conversion path from distance parameters to intensity parameters, where each processing step strictly depends on the parameters determined in the previous steps, ensuring the continuity and reliability of the calculation results.

[0047] Furthermore, the process of comparing the initial intensity value with the normalized reference value used when calculating the uncorrected disturbance propagation distance through the nonlinear attenuation function in step S211223 specifically includes the following steps: Step S2112231: Perform a proportional calculation between the initial intensity value and the normalized reference value; the initial intensity value is used as the dividend and the normalized reference value is used as the divisor to calculate the ratio between the two, forming a dimensionless scaling factor. The scaling factor reflects the relative magnitude of the intensity level of the current estimated point relative to the system calculation reference. Step S2112232: Multiply the scaling factor with the system's preset reference strength constant; the reference strength constant is a fixed parameter with strength dimensions, and its function is to give the obtained dimensionless scaling factor a new physical meaning and dimension of strength in actual engineering. Step S2112233: The scaling factor is converted into an intensity value with a clear physical meaning and dimension; the final value after conversion is the standardized disturbance intensity value; the difference in magnitude that may exist in different calculation stages is eliminated, so that the intensity value can be directly compared with the subsequent critical disturbance intensity threshold under a unified dimension and standard.

[0048] Preferably, this embodiment eliminates the dimensional difference between the initial intensity value and the normalized reference value through proportional calculation, forming a proportional factor that reflects the relative intensity level; by introducing a reference intensity constant, the dimensionless proportional factor is converted into an intensity value with actual physical meaning; finally, the standardization of the disturbance intensity value is achieved, ensuring that the value is directly comparable to the critical disturbance intensity threshold under a unified dimensional system, and eliminating the comparison deviation caused by the difference in magnitude in different calculation stages.

[0049] In this process, a scaling factor is derived from the initial intensity value and the normalized benchmark value, and then the scaling factor is combined with the reference intensity constant to form the standardized perturbation intensity value. This continuous process ensures the standardized transformation of the intensity value, establishing a unified and reliable quantitative benchmark for subsequent threshold comparisons.

[0050] Furthermore, such as Figure 4 As shown, the process of setting the preset variable rate threshold in step S3 specifically includes the following steps: Step S31: The structural looseness index is mapped to represent the rheological properties of the rock mass, and a parameter directly related to the time-dependent deformation capacity of the rock mass is output, called the deformation sensitivity coefficient. The deformation sensitivity coefficient is used to decompose the minimum compression amount on a time scale, and the minimum compression amount is taken as the total deformation amount. Combined with the reasonable stable period determined in the engineering construction plan, the upper limit of the deformation amount per unit time under the premise of ensuring that the minimum compression amount is not exceeded, i.e., the critical compression rate is obtained. Step S32: Introduce a stable excavation step distance as a spatial constraint condition, couple the critical compression rate with the stable excavation step distance for analysis, analyze the mutual constraint relationship in the spatiotemporal dimension, and derive the allowable deformation rate benchmark value that matches the spatial advance during the implementation of a single excavation step distance, i.e., the initial deformation rate threshold. Step S33: Based on the enhancement of deformation control capability by the support structure, the initial variable rate threshold is corrected; according to the additional constraint stiffness provided by the support system, the value of the initial variable rate threshold is increased to form the final preset variable rate threshold for engineering monitoring.

[0051] Preferably, this embodiment establishes the correlation between rock mass rheological properties and deformation sensitivity coefficient through the mapping transformation of the structural looseness index. Based on the stable engineering period, the minimum compression amount is decomposed into a critical compression rate, forming a deformation control benchmark in the time dimension. Combined with the spatial constraints of the stable excavation step distance, the critical compression rate is transformed into an initial variable rate threshold matching the construction advance through spatiotemporal coupling analysis, achieving coordination between deformation control and construction progress. By introducing the constraint stiffness of the support system, the initial threshold is strengthened and corrected, forming a variable rate threshold that takes into account both the inherent properties of the rock mass and the engineering control capability, ultimately establishing a deformation monitoring standard with spatiotemporal adaptability and engineering operability. In this process, the deformation sensitivity coefficient and critical compression rate are derived from the structural looseness index and the minimum compression amount, and then combined with the stable excavation step distance to form an initial variable rate threshold. Finally, the preset variable rate threshold is determined based on the support reinforcement effect. This ensures that the threshold setting deeply integrates multiple factors such as rock mass properties, deformation control objectives, construction advance, and support effectiveness.

[0052] Furthermore, step S32, which derives the baseline value of the deformation rate that is allowed during a single excavation step and matches the spatial advance, specifically includes the following steps: Step S321: Using the stable excavation step distance as a spatial reference, by dividing it by the standard excavation cycle period specified in the construction specifications, it is converted into a parameter in the time dimension, called the equivalent exposure time; Step S322: Treat the critical compression rate as a theoretical upper limit that is uniformly distributed over time. Based on a specific time period defined by the equivalent exposure time, adaptively adjust the theoretical upper limit to generate a deformation capacity budget for single-cycle excavation. Step S323: Divide the deformation capacity budget by the equivalent exposure time, and the resulting quotient is the initial deformation rate threshold; ensure that the cumulative deformation of the surrounding rock does not exceed the overall control target based on the minimum compression amount within the implementation time of a single stable excavation step, while its deformation rate matches the spatial advance.

[0053] Preferably, in this embodiment, the equivalent exposure time and deformation capacity budget are derived from the critical compression rate and stable excavation step distance, and then the initial variable rate threshold is finally formed through the correction of the spatiotemporal compatibility factor; this ensures that the time scale requirements of deformation control and the spatial construction progress are deeply integrated and mutually constrained.

[0054] like Figures 5-9 As shown, this embodiment also provides an embodiment of the excavation support system for severely squeezed and deformed sections of soft rock tunnels. In this embodiment, the excavation support system for severely squeezed and deformed sections of soft rock tunnels is applied to the excavation support method for severely squeezed and deformed sections of soft rock tunnels as described in the above embodiment. The excavation support system for severely squeezed and deformed sections of soft rock tunnels includes an initial support system 1, reserved core soil 2, upper bench 3, middle bench 4, lower bench 5, advanced small guide pipe 6, advanced large pipe shed 7, radial consolidation grouting 8, clearance anchor 9, drainage hole of side arch deepening system 10, advanced support system 11, advanced consolidation grouting 12, reserved deformation amount 13, steel support 14, thin steel plate 15, locking foot large pipe shed 16, welded part 17, locking foot connecting bar 18, and locking foot anchor 19. Among them, such as Figure 5 As shown, the initial support system 1 is divided into an upper step 3, a middle step 4, and a lower step 5; a core soil 2 is reserved on the upper step 3. like Figure 6 As shown, an advanced small guide pipe 6 is connected to the outside of the initial support system 1, and an advanced large pipe shed 7 is provided. like Figure 7As shown, several radial consolidation grouting 8, clearance anchors 9, and drainage holes 10 of the side arch deepening system are connected to the initial support system 1; a reserved deformation amount 13 is set outside the initial support system 1; an advanced support system 11 is set outside the reserved deformation amount 13; and several advanced consolidation grouting 12 are set inside the initial support system 1. like Figure 8 As shown, H-beam supports 14 are installed, and the two steel supports of the top arch and the side wall are welded together by a thin steel plate 15, and a locking pipe 16 is used to connect the steel support and the thin steel plate. like Figure 9 As shown, two anchor bolts are installed at the joint and arch foot, and the anchor bolts 18, 19 and H-beam support 14 are welded together; a double-layer steel mesh is hung on the inner wall of the tunnel and C20 coarse fiber concrete is sprayed, and the clearance anchor bolts 9 are installed; after the initial support is completed, the drainage holes 10 of the side arch are deepened and radial consolidation grouting 8 is applied.

[0055] Preferably, in this embodiment, advanced small guide pipes 6 and advanced large pipe sheds 7 are installed on the tunnel arch, and advanced consolidation grouting is performed; after excavation, H-shaped steel supports 14 are installed, and a thin steel plate 15 is welded between the two steel supports of the arch and the sidewall, and a locking large pipe shed 16 is used to connect the steel support and the thin steel plate. Two locking anchor rods are installed at the joint and the arch foot, and the locking connecting bar 18, locking anchor rod 19 and H-shaped steel support are welded together; a double-layer steel mesh is hung on the inner wall of the tunnel and C20 coarse fiber concrete is sprayed, and clearance anchor rods 9 are installed; after the initial support is completed, the drainage holes 10 of the side arch are deepened, and radial consolidation grouting 8 is performed; all steel supports are made of H-shaped steel, and anchor rods are used for locking at the joint and the arch foot. The two steel supports of the arch and the sidewall are welded together by steel plates, and a hole is opened in the middle part of the overlapping area of ​​the steel plate and the steel support. A large pipe shed is driven into the hole for locking. H-beams are then installed on each base plate as temporary cross bracing.

[0056] In summary, this embodiment determines the total length of the steps and the amount of deformation to be reserved based on the surrounding rock conditions; construction of the tunnel arch pre-support system: before excavation, large pipe sheds and small guide pipes are installed around the tunnel arch, followed by pre-consolidation grouting; after tunnel excavation, H-beam supports are erected for the arch, sidewalls and bottom slab, and anchor bolts are installed; after tunnel excavation, shotcrete is applied to the inner wall of the tunnel, double-layer steel mesh is hung and clearance anchor bolts are installed; after the initial support is completed, the drainage holes of the tunnel surrounding rock deepening system are filled and radial consolidation grouting is performed to improve the strength of the surrounding rock around the tunnel.

[0057] like Figure 10 As shown, this embodiment provides an embodiment of an electronic device. In this embodiment, the electronic device 20 includes a processor 201 and a memory 202 coupled to the processor 201.

[0058] The memory 202 stores program instructions for implementing the excavation and support method for severely squeezed and deformed sections of soft rock tunnels in any of the above embodiments.

[0059] The processor 201 is used to execute program instructions stored in the memory 202 for excavation and support of severely squeezed and deformed sections of soft rock tunnels.

[0060] The processor 201 can also be referred to as a CPU (Central Processing Unit). The processor 201 may be an integrated circuit chip with signal processing capabilities. The processor 201 can also be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. A general-purpose processor can be a microprocessor or any conventional processor.

[0061] Furthermore, Figure 11 This is a schematic diagram of the structure of a storage medium according to an embodiment of this application. The storage medium 21 of this embodiment stores program instructions 211 capable of implementing all the above methods. These program instructions 211 can be stored in the storage medium in the form of a software product, including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks, or terminal devices such as computers, servers, mobile phones, and tablets.

[0062] In the several embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0063] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated units described above can be implemented in hardware or as software functional units. The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

[0064] The specific embodiments of the invention have been described in detail above, but these are merely examples, and the invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications or substitutions to the invention are also within the scope of this invention. Therefore, all equivalent transformations, modifications, and improvements made without departing from the spirit and principles of this invention should be included within the scope of this invention.

Claims

1. A method for excavation and support of severely compressed and deformed sections of soft rock tunnels, characterized in that, The method for excavating and supporting severely compressed and deformed sections of soft rock tunnels includes the following steps: Obtain the surrounding rock condition and determine the step length and reserved deformation amount based on the surrounding rock condition; constrain the surrounding rock deformation and block groundwater seepage based on the reserved deformation amount; construct the arch support system, install large pipe sheds and small pipes around the tunnel arch before excavation, and carry out advanced consolidation grouting. The excavation and support work space is determined according to the step length. After the tunnel is excavated in short advances in steps, rigid support construction is carried out to limit the displacement of the surrounding rock surface. After the tunnel is excavated, H-beam supports are erected for the top arch, side walls and bottom plate, and anchor bolts are installed. After the anchor bolts are installed, initial support reinforcement is carried out; after the tunnel is excavated, the inner wall of the tunnel is sprayed with concrete, double-layer steel mesh is hung and clearance anchor bolts are installed; when the initial support is completed and the deformation of the surrounding rock tends to the preset rate threshold, the drainage holes of the tunnel surrounding rock deepening system are filled and radial consolidation grouting is carried out. The process of determining the excavation and support working space based on the step length includes the following steps: Based on the stable excavation step distance, the longitudinal disturbance range of the tunnel face is deduced, which describes the significant stress adjustment of the longitudinal depth of the unexcavated rock mass caused by the excavation activities. The longitudinal disturbance range of the tunnel face is combined with the designed excavation profile of the tunnel to define the initial working envelope. The initial working envelope represents the theoretical space volume required for all large mechanical equipment to perform core operations in a single cycle of excavation. Using the minimum compression amount as the quantitative basis for boundary shrinkage, uniform radial displacement reduction is carried out from the inner side of the top arch, sidewall and bottom plate of the initial working envelope to generate a working space after convergence compensation that takes into account the inevitable convergence of the surrounding rock. Based on the convergence compensation working space and the installation process requirements of the support structure, the interference-free installation domain of the rigid support is clearly defined. The process of defining the initial operational envelope includes the following steps: The stable excavation step distance is used as the mechanical excitation scale for a single advance of the face. The mechanical excitation scale is combined with the structural looseness index. The structural looseness index is converted into a stress wave transmission attenuation coefficient to quantify the agility and persistence of excavation disturbance in the rock medium. The stress wave transmission attenuation coefficient is used to perform a transmission correction on the mechanical excitation scale and calculate the stress redistribution front depth. The stress redistribution front depth is used as a dynamic boundary and spatially superimposed with the static geometric boundary of the tunnel design excavation profile. The design excavation profile is stretched along the tunnel axis and extended in front of the tunnel face. The length of the extension is the stress redistribution front depth, thus constructing an excavation influence prism in three-dimensional space. An operational adaptation transformation is carried out on the excavation-affected prism. Taking into account the minimum turning radius, working arm range, and safe distance of large machinery and equipment and their collaborative operations, a free operating domain for the equipment without internal structural interference is defined inside the excavation-affected prism. The free operating domain for the equipment is the defined initial operating envelope.

2. The method for excavation and support of severely compressed and deformed sections of soft rock tunnels according to claim 1, characterized in that, The process of calculating the depth of the stress redistribution front includes the following steps: The mechanical excitation scale is coupled with the stress wave propagation attenuation coefficient. The mechanical excitation scale is used as the input and substituted into the nonlinear attenuation function that characterizes the energy absorption characteristics of the rock mass. The shape of the nonlinear attenuation function is uniquely determined by the stress wave propagation attenuation coefficient. Through the calculation of the nonlinear attenuation function, an uncorrected disturbance propagation distance is output. The uncorrected disturbance propagation distance is compared and calibrated with the critical disturbance intensity threshold. Through iterative feedback, the longitudinal distance corresponding to the decrease of the disturbance intensity to the critical disturbance intensity threshold under the action of the nonlinear decay function is found. The critical disturbance intensity threshold is derived from the definition of the critical energy density required for irreversible adjustment of the rock mass microstructure. It is a constant parameter derived from the constitutive properties of the rock mass. The longitudinal distance, after calibration with the critical disturbance intensity threshold, is confirmed as the depth of the stress redistribution front; that is, the longitudinal disturbance range of the working face, indicating the farthest longitudinal boundary that can be affected by the mechanically significant stress adjustment triggered by this excavation.

3. The method for excavation and support of severely compressed and deformed sections of soft rock tunnels according to claim 2, characterized in that, The process of reducing the disturbance intensity to the longitudinal distance corresponding to the critical disturbance intensity threshold includes the following steps: The uncorrected perturbation propagation distance is redefined as the initial estimated propagation limit, located on a perturbation intensity decay curve described by a nonlinear decay function; meanwhile, the critical perturbation intensity threshold is regarded as a threshold horizontal line parallel to the distance axis. Starting with the initial estimated propagation limit, the perturbation intensity value corresponding to the starting point on the perturbation intensity decay curve is calculated; the perturbation intensity value is compared with the critical perturbation intensity threshold for the first time, and the difference is quantified as the primary intensity surplus; Based on the direction and magnitude of the primary strength surplus, a distance-strength feedback loop is initiated. If a primary strength surplus exists, it indicates that the disturbance strength is still higher than the critical threshold at the current estimated distance, and it is necessary to search for the intersection point along the decay curve in the direction of increasing distance. Conversely, it searches in the direction of decreasing distance. The feedback loop adjusts the assumed longitudinal distance value and repeatedly substitutes it into the nonlinear decay function to calculate the corresponding disturbance strength until a certain longitudinal distance is found that makes the difference between the calculated disturbance strength and the critical disturbance strength threshold less than a preset tolerance.

4. The method for excavation and support of severely compressed and deformed sections of soft rock tunnels according to claim 3, characterized in that, The process of calculating the disturbance intensity value corresponding to the starting point on the disturbance intensity decay curve includes the following steps: The initial estimated propagation limit is multiplied by the reciprocal of the stress wave propagation attenuation coefficient to generate an intermediate parameter, called the reference energy level. Multiplying the reference energy level by the intensity correction factor yields the unnormalized initial intensity value; the intensity correction factor serves as the mechanical excitation scale of the input parameter, and its specific value is inversely proportional to the square root of the mechanical excitation scale. The initial intensity value is compared with the normalized reference value used when calculating the uncorrected disturbance propagation distance through a nonlinear decay function. The ratio is taken and multiplied by the system's preset reference intensity constant to finally obtain the standardized disturbance intensity value.

5. The method for excavation and support of severely compressed and deformed sections of soft rock tunnels according to claim 4, characterized in that, The process of comparing the initial intensity value with the normalized reference value used when calculating the uncorrected disturbance propagation distance using a nonlinear attenuation function includes the following steps: The initial intensity value is proportional to the normalized reference value. The initial intensity value is used as the dividend and the normalized reference value is used as the divisor. The ratio between the two is calculated to form a dimensionless scaling factor. The scaling factor reflects the relative magnitude of the intensity level of the current estimated point relative to the system calculation reference. The scaling factor is multiplied by the system's preset reference strength constant. The reference strength constant is a fixed parameter with strength dimensions. Its function is to give the obtained dimensionless scaling factor a new physical meaning and dimension of strength in actual engineering. The scaling factor is converted into an intensity value with a clear physical meaning and dimensions; the final value after conversion is the standardized disturbance intensity value.

6. The method for excavation and support of severely compressed and deformed sections of soft rock tunnels according to claim 1, characterized in that, The process of setting the preset variable rate threshold includes the following steps: The structural looseness index is mapped to characterize the rheological properties of the rock mass, and a parameter directly related to the time-dependent deformation capacity of the rock mass is output, called the deformation sensitivity coefficient. The deformation sensitivity coefficient is used to decompose the minimum compression amount on a time scale, and the minimum compression amount is taken as the total deformation. Combined with the reasonable stable period determined in the engineering construction plan, the upper limit of the deformation amount per unit time under the premise of ensuring that the minimum compression amount is not exceeded is obtained, i.e., the critical compression rate. By introducing a stable excavation step distance as a spatial constraint, the critical compression rate and the stable excavation step distance are coupled and analyzed to analyze their mutual constraints in the spatiotemporal dimensions. The allowable deformation rate benchmark value that matches the spatial advance during the implementation of a single excavation step distance is derived, i.e., the initial deformation rate threshold. Based on the enhanced deformation control capability of the support structure, the initial variable rate threshold is modified; according to the additional constraint stiffness provided by the support system, the value of the initial variable rate threshold is increased to form the final preset variable rate threshold for engineering monitoring.

7. A support system for excavating severely deformed sections of soft rock tunnels, applied to the excavation and support method for severely deformed sections of soft rock tunnels as described in any one of claims 1 to 6, characterized in that, The excavation support system for the severely squeezed and deformed section of the soft rock tunnel includes: initial support system, reserved core soil, upper bench, middle bench, lower bench, advanced small guide pipe, advanced large pipe roof, radial consolidation grouting, clearance anchor bolts, drainage holes of the side-top arch deepening system, advanced support system, advanced consolidation grouting, reserved deformation amount, steel support, thin steel plate, locking foot large pipe roof, welded parts, locking foot connecting bars, and locking foot anchor bolts; The initial support system is divided into upper, middle, and lower steps; the upper step has reserved core soil; advanced small guide pipes are connected to the outside of the initial support system, and advanced large pipe sheds are also provided; several radial consolidation grouting, clearance anchors, and drainage holes of the side-top arch deepening system are connected to the initial support system; a reserved deformation amount is set outside the initial support system; an advanced support system is set outside the reserved deformation amount; and several advanced consolidation grouting is set inside the initial support system. Install H-beam supports. Weld a thin steel plate between the two steel supports of the top arch and the side wall, and use a locking foot pipe to connect the steel support and the thin steel plate. Install two locking foot anchors at the joint and the arch foot, and weld the locking foot connecting bar, locking foot anchor and H-beam supports. Hang double-layer steel mesh on the inner wall of the tunnel and spray C20 coarse fiber concrete, and install clearance anchors. After the initial support is completed, deepen the drainage holes of the side arch and apply radial consolidation grouting.

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