CN110617072A - Tunnel excavation construction method for obliquely passing existing operation tunnel at minimum clear distance - Google Patents

Abstract

The invention relates to a tunnel excavation construction method for obliquely penetrating an existing operating tunnel with a minimum clear distance, comprising the following steps: Step 1: obtaining the distribution of rock layers in front of the tunnel face to be excavated and physical and mechanical parameters of surrounding rocks; Step 2 : Carry out asymmetric grouting reinforcement to the surrounding rock in front of the face; Step 3: Reserve core soil and excavate the excavation groove by cutting and grinding; Step 4: Install the supporting structure in the excavation groove; Step 5 : Excavate the reserved core soil by cutting and grinding; monitor the support stress state and displacement of the existing operating tunnels in steps 3 and 5, and step 6: obtain the differential settlement of the existing operating tunnels; Step 7: Grouting the surrounding rock below the area where the differential settlement value of the existing operating tunnel is greater than the set value; Step 8: Using the method of Steps 1-7, grouting and excavation in multiple steps are performed in sequence. The construction method of the invention can effectively maintain the stability of the existing operating tunnel.

Description

A tunnel excavation construction method for obliquely passing through an existing operating tunnel with a minimal clear distance

technical field

The invention relates to the technical field of tunnels and underground engineering, in particular to a tunnel excavation construction method for obliquely penetrating an existing operating tunnel with a minimum clear distance.

Background technique

The urban subway operating tunnel lines are generally distributed in a network, and it is inevitable that the lines will cross each other. During the construction of new subway lines, there are a lot of cases where the proposed tunnels pass through the existing operating tunnels. The excavation of the underpassing tunnel has a significant disturbance impact on the existing operating tunnels, which often lead to problems such as settlement of the existing operating tunnels, deformation and cracking of the lining structure, and voiding of the track bed, especially when the proposed tunnel obliquely underpasses the existing operating tunnel with a very small clear distance. When there are operating tunnels, it will cause obvious torsion effect of the existing operating tunnels, and uneven deformation will occur on the axis section of the vertical operating tunnels. Small, the tunnel structure may suffer torsional failure.

Drilling and blasting method is a commonly used construction method for the working condition of obliquely penetrating existing operating tunnels with extremely small clear distance. The inventor found that the above method has the following shortcomings: 1. From the perspective of short-term construction, the blasting impact force during the drilling and blasting construction process will cause strong disturbance to the rock mass above the face of the proposed tunnel, and the surrounding rock strength is reduced. When the distance between the construction tunnel and the existing operating tunnel above is small, the existing operating tunnel may become unstable; ② From the perspective of long-term operation, the mechanical properties of the rock mass below the existing operating tunnel are reduced due to drilling and blasting construction, which resists long-term operating trains. The capacity of the dynamic load decreases, and the foundation of the existing operating tunnel may suffer fatigue damage, which cannot guarantee the long-term stability of the operating tunnel.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a tunnel excavation construction method for obliquely passing through the existing operating tunnels with a minimum clear distance, which can effectively reduce the torsional effect and disturbance on the existing operating tunnels, and ensure that the Stability of existing operating tunnels.

To achieve the above object, the present invention adopts the following technical solutions:

A tunnel excavation construction method for obliquely passing through an existing operating tunnel with a minimum clear distance, comprising the following steps:

Step 1: Based on the geological exploration data and the test results of advanced drilling and coring, obtain the distribution of rock formations and the physical and mechanical parameters of the surrounding rock within the influence area of the tunnel excavation in front of the tunnel face to be excavated.

Step 2: Within a step range along the axis of the tunnel to be excavated, perform asymmetric grouting reinforcement on the surrounding rock in front of the face of the tunnel to be excavated to improve the surrounding area of the overlapping area between the tunnel to be excavated and the existing operating tunnel. mechanical properties of rock.

Step 3: Reserve core soil, excavate the rock mass in front of the face by cutting and grinding, and excavate trenches with a depth equal to the step distance set along the contour line of the tunnel edge to be excavated, and monitor existing operations during the excavation process. Tunnel support stress state and displacement.

Step 4: Install the support structure in the excavation trench.

Step 5: The reserved core soil is excavated by cutting and grinding, and the support stress state and displacement of the existing operating tunnels are monitored during the excavation process.

Step 6: According to the support stress state and displacement state of the operating tunnel obtained in steps 3 and 5, the differential settlement of different positions on the same section of the existing operating tunnel is obtained.

Step 7: grouting the surrounding rock below the area where the differential settlement value of the existing operating tunnel is greater than the set value through the face of the tunnel to be excavated, so as to make the differential settlement of the area where the differential settlement value of the existing operating tunnel is greater than the set value. The value is less than the set value.

Step 8: Using the methods from Step 1 to Step 7, perform grouting and excavation work in multiple steps along the axis direction of the tunnel to be excavated in sequence until all grouting and excavation work is completed.

Further, in the step 2, the area within the horizontal range of the surrounding rock reinforced by asymmetric grouting is the area where the tunnel to be excavated and the existing operating tunnel are projected and overlapped in the horizontal plane, and the area within the vertical range is the tunnel to be excavated. The area between the contour line and the existing operating tunnel contour line.

Further, in the step 2, the grouting material adopts cement single liquid slurry, the water-cement ratio of the cement slurry is in the range of 0.8-1, and the water-cement ratio range of the cement slurry cannot be too high or too low, and an excessively high water-cement ratio It will lead to too much free water in the grouting reinforcement range, and the grouting reinforcement effect does not meet the requirements. Too low water-cement ratio will lead to poor grouting ability of the slurry, and the filling rate of the surrounding rock cracks will be too low, and the grouting reinforcement effect will not be good. fulfil requirements.

Further, in the step 3, the excavation method of the excavation groove is as follows: firstly, the first excavation groove portion is cut and ground along the contour line on one side wall of the tunnel, and then the other side edge is cut and ground along the contour line. The second excavation groove portion is finally cut and ground along the edge contour of the tunnel vault to form the third excavation groove portion.

Further, in the step 5, the cutting and grinding motion trajectory of the reserved core soil is a bottom-up S-shaped trajectory, and the excavation depth of the core soil is equal to the step distance.

Further, before the steps 3 and 5 are carried out, a plurality of monitoring points are set in the existing operating tunnels to monitor the stress state and displacement of the support, and the monitoring points are set in the existing operating tunnels. On a plurality of monitoring sections in the area, each monitoring section is set with a plurality of monitoring points, and the method for determining the set area is: determine the area corresponding to the face of the tunnel to be excavated in the existing operating tunnel, and use the The area is the center, the set distance along the front and rear directions of the existing operating tunnel axis is the boundary of the set area, and the area between the two boundaries is the set area.

Further, the set distance is 1.5 times the diameter of the tunnel to be excavated, and the distance between adjacent monitoring sections is equal to the step distance.

Further, in the same monitoring section, one monitoring point is set at the vault position, the vault bottom position and the two vault waist positions of the existing operating tunnel, and one monitoring point is inserted at equal intervals between the monitoring points of the vault and the two vault waists. A monitoring point is inserted at an equal distance between the monitoring points of the arch bottom and the two arch waists respectively.

Further, in the step 7, the grouting material adopts cement single-liquid slurry, the water-cement ratio of the cement slurry is in the range of 0.8-1, and the water-cement ratio range of the cement slurry should not be too high or too low, and an excessively high water-cement ratio It will lead to too much free water in the grouting range, and the grouting reinforcement effect and lifting effect will not meet the requirements. Too low water-cement ratio will lead to poor grouting of the slurry, and the filling rate of surrounding rock fissures will be too low, which will lead to grouting reinforcement. The effect and lifting effect do not meet the requirements.

Further, in the step 7, the set value is 0.3 cm, which does not exceed the differential settlement limit that can ensure the safety of train operation in the existing operating tunnel and the safety of the lining structure.

Beneficial effects of the present invention:

1. In the construction method of the present invention, before excavation of the face, grouting reinforcement is performed on the surrounding rock area of the overlapping part of the existing operating tunnel and the tunnel to be excavated, which can effectively reduce the amount of damage to the existing operating tunnel during the construction of the tunnel to be excavated. Spatial torsion effect reduces uneven settlement and uneven stress of existing operating tunnels.

2. In the construction method of the present invention, the excavation groove is excavated by cutting and grinding, and then the supporting structure is directly installed. This method greatly reduces the disturbance to the surrounding rock, thereby ensuring the surrounding area under the existing operating tunnel. The stability of rock mechanical properties ensures the bearing capacity of surrounding rock for existing operating tunnels.

3. The construction method of the present invention directly installs the support structure after excavating the trench, shortens the time from excavation to the support operation, and is more conducive to the safety of the project.

4. In the construction method of the present invention, core soil is reserved when excavating the excavation groove, which is beneficial to ensure the stability of the face during the excavation and support operations.

5. The construction method of the present invention can monitor the support stress state and displacement state of the existing operating tunnel, and then obtain the area with excessive settlement of the existing operating tunnel, and perform grouting under the area to make the existing operation in the area. The lifting of the tunnel ensures that the settlement value of the operating tunnel is within the allowable limit.

Description of drawings

The accompanying drawings that constitute a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute a limitation to the present application.

Fig. 1 is the schematic diagram of the grouting reinforcement surrounding rock area within one step of the two ends of the intersection of the existing operating tunnel and the tunnel to be excavated according to Embodiment 1 of the present invention;

Fig. 2 is the A-direction cross-sectional schematic diagram in Fig. 1 of the present invention;

Fig. 3 is the B-direction cross-sectional schematic diagram in Fig. 1 of the present invention;

4 is a schematic diagram of a transverse cross-section of excavation trenches and core soil excavation in Example 1 of the present invention;

Fig. 5 is the longitudinal section schematic diagram of excavation trench and core soil excavation in Example 1 of the present invention;

6 is a schematic diagram of the arrangement of monitoring points in the monitoring section of an existing operating tunnel according to Embodiment 1 of the present invention;

Among them, 1. Existing operating tunnel, 2. Tunnel to be excavated, 3. Intersection, 4. Face, 4-1. Upper working face, 4-2. Lower working face, 5. Grouting reinforcement enclosure Rock area, 6. Step distance, 7. Grouting hole, 8. Excavation groove, 8-1. First excavation groove part, 8-2. Second excavation groove part, 8-3. Third excavation Groove, 9. Left side tunnel wall, 10. Right side tunnel side wall, 11. Vaulted tunnel side wall, 12. Support structure, 13. Monitoring point, 14. Core soil.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components, and/or combinations thereof.

For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, it only means that the directions of up, down, left and right are consistent with the drawings themselves, and do not limit the structure. It is for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as a limitation of the present invention.

As described in the background art, at present, when constructing a tunnel that is located under the existing operating tunnel, crosses the existing operating tunnel, and has a small clear distance from the existing operating tunnel, the stability of the existing operating tunnel is not guaranteed. In view of the above problems, the present application proposes a tunnel excavation construction method that obliquely penetrates an existing operating tunnel with a very small clear distance.

In Example 1 of a typical implementation of the present application, as shown in Figures 1-5, the vaults of the existing operating tunnels are buried at a depth of 5.1-13.5m, mainly located in moderately weathered granite strata, and the thickness of the overlying rock is 0.4-11.5m. The tunnel structure is a horseshoe-shaped section, the tunnel is constructed by the mining method, the support form is the primary support + secondary lining composite lining, and the design dimension of the tunnel support is 6.3m × 6.6m in width and height. The lower part of the tunnel to be excavated has a vault depth of 18.3m-20.8m. The tunnel body is mainly located in strongly weathered, moderately weathered and slightly weathered granite. The mining method is designed to be constructed by ascending and descending steps. The excavation step distance is 0.5m. Section, the support form is primary support + secondary lining composite lining, and the design dimension of tunnel support is 7m × 7.4m in width and height. The lower tunnel to be excavated obliquely penetrates the existing operating tunnel with a small clear distance, and the angle between the axis of the lower tunnel and the existing operating tunnel is 25°. It belongs to the first-level major risk source.

In this embodiment, the part of the tunnel 2 to be excavated that does not pass through the existing operating tunnel 1 is constructed by using the step method. When the tunnel to be excavated is constructed to obliquely descends through the part 3 of the existing operating tunnel, the face 4 is covered by the steps. It is divided into upper working face 4-1 and lower working face 4-2.

Its specific construction includes the following steps:

Step 1: Comprehensive geological exploration data and advanced drilling core test results to obtain the distribution of rock formations and physical and mechanical parameters of surrounding rock within the influence area of tunnel excavation in front of the tunnel. The step 1 adopts the common method of existing tunnel construction. The specific steps are not described in detail here.

Step 2: As shown in Figure 1-3, perform asymmetric grouting reinforcement on the surrounding rock in front of the upper working face of the tunnel face to be excavated. Specifically, a distance range of 6 steps along the axis of the tunnel to be excavated Inside, the surrounding rock between the upper contour line of the tunnel to be excavated and the lower contour line of the existing operating tunnel is grouted for reinforcement, and the surrounding rock area 5 for grouting reinforcement is the vertical direction of the tunnel to be excavated and the existing operating tunnel. The surrounding rock area between the overlapping parts, that is, within a step range in the axial direction of the tunnel to be excavated, the area within the horizontal range of the surrounding rock reinforced by asymmetric grouting is the projection of the tunnel to be excavated and the existing operating tunnel in the horizontal plane The overlapping area, the area within the vertical range is the area between the outline of the tunnel to be excavated and the outline of the existing operating tunnel.

The grouting reinforcement is carried out by grouting with small conduits, and a plurality of advanced conduits are drilled into the rock mass in front of the face through the grouting holes 7 provided on the upper working face of the face, and the leading conduit is used to move to the upper working face. For grouting with square surrounding rock, the insertion depth and angle of the advanced conduit should meet the requirements of the surrounding rock area that needs grouting reinforcement. Too high or too low, too high water-cement ratio will lead to too much free water in the grouting reinforcement range, and the grouting reinforcement effect will not meet the requirements, too low water-cement ratio will lead to poor injectability of the grout and cracks in the surrounding rock. The filling rate is too low, and the grouting reinforcement effect does not meet the requirements, and the final water-cement ratio of the cement single slurry is controlled within the range of 0.8-1. During the grouting process, when the grouting pressure reaches 1MPa and the grouting volume of a single hole reaches the set standard value, the grouting operation of the grouting hole is stopped.

Step 3: As shown in Figure 4-5, remove the leading conduit, and use the cantilever roadheader to excavate the excavation groove 8 on the upper working surface of the face by cutting and grinding. Specifically, reserve the core soil 14, First, the first excavation groove portion 8-1 is excavated along the contour line of the left tunnel side wall 9 on one side of the upper working face, and then the second excavation groove portion 8-1 is excavated along the contour line of the right tunnel side wall 10 on the other side of the upper working face. The groove portion 8-2 is excavated, and finally the third excavation groove portion 8-3, the first excavation groove portion, the second excavation groove portion and the third excavation groove portion are excavated along the contour line position of the side wall 11 of the vaulted tunnel of the tunnel. The trough portions together form a trough, the depth of which is equal to the length of one step.

During the excavation of the trench, the support stress state and displacement of the existing operating tunnels are monitored in real time. The support stress state includes the stress and strain state of the lining, and the displacement state includes the vertical and horizontal displacement of the support.

During the working process of the cantilever roadheader, the side of the roadhead plays a cutting role on the soil, and the front end of the roadhead faces the soil and grinds the soil. Compared with the traditional drilling and blasting method, the excavation can be greatly reduced. When the construction disturbs the surrounding rock, the core soil is reserved when excavating the excavation groove, which can effectively maintain the stability of the face.

Step 4: After the construction of the excavation groove is completed, the initial support structure 12 is directly installed inside the excavation groove. Specifically, the grid arch frame is erected in the excavation groove. After the grid arch frame is erected, the quick-setting concrete is injected to make the The grid arch is embedded in concrete to form the initial support structure.

Step: 5: After the construction of the initial support structure is completed, use the cantilever roadheader to excavate the reserved core soil by cutting and grinding. The left and right are circulated in an S-shaped trajectory until the excavation is completed, and the excavation depth of the core soil is equal to the distance of one step.

During the excavation of the core soil, the support stress state and displacement of the existing operating tunnels are monitored in real time. The support stress state includes the stress and strain state of the lining, and the displacement state includes the vertical and horizontal displacement of the support.

During the process of step 5, the lower working face of the tunnel face is excavated at the same time, the excavation depth is equal to the distance of one step, and the supporting structure is erected at the same time, and the method can adopt the existing step method construction method. This will not be described in detail.

Step 6: According to the support stress state and displacement state of the operating tunnel obtained in steps 3 and 5, the differential settlement of different positions on the same section of the existing operating tunnel is obtained.

Step 7: grouting the surrounding rock below the area where the differential settlement value of the existing operating tunnel is greater than the set value through the face of the tunnel to be excavated, so as to make the differential settlement of the area where the differential settlement value of the existing operating tunnel is greater than the set value. The value is less than the set value. In this embodiment, the set value does not exceed the differential settlement limit that can ensure the safety of the train operation and the safety of the lining structure of the existing operating tunnel. The set value in this embodiment adopts 0.3cm , when the differential settlement difference between different positions on the same section of the existing operating tunnel reaches 0.3 cm, the differential settlement value is considered to be too large, and the surrounding rock area under the part where the differential settlement value of the existing operating tunnel is too large is grouted. Grouting is to lift the part of the existing operating tunnel whose differential settlement value is too large to meet the requirements. The range of cement ratio should not be too high or too low. Too high water-cement ratio will lead to too much free water in the grouting reinforcement range, and the effect of grouting reinforcement does not meet the requirements. Too low water-cement ratio will lead to the injectability of the grout. Poor, the filling rate of the surrounding rock cracks is too low, and the grouting reinforcement effect does not meet the requirements, and the final water-cement ratio of the cement single slurry is controlled between 0.8-1.

Step 8: Using the method from Step 1 to Step 7, along the axis of the tunnel to be excavated, perform grouting and excavation work in multiple steps in sequence until the tunnel to be excavated obliquely penetrates the part of the existing operating tunnel. Excavation completed.

Before the step 3 is carried out, multiple monitoring points are set in the existing operating tunnel to monitor the support stress state and displacement of the existing tunnel. As shown in Figure 6, the setting in the existing operating tunnel Multiple monitoring sections are set up in the area, the distance between each monitoring section is 0.5m, and eight monitoring points 13 are set on each monitoring section, one at the top of the arch, one at the bottom of the arch, and one at the waist of the arch. A monitoring point is inserted equidistantly between the above-mentioned adjacent monitoring points, with a total of eight monitoring points. Corresponding monitoring instruments are installed at the monitoring points to monitor the stress state and displacement state of the support. The equipment is sufficient, and detailed description is not given here.

The method for determining the set area on the existing operating tunnel is: before step 2, determine the corresponding area of the upper working face of the face in the existing operating tunnel, and extend the corresponding area forward and backward along the axis direction of the existing operating tunnel. The distance is obtained from the two boundaries of the set area, and the area between the two boundaries is the set area, and the set distance requirement is not less than the excavation influence range of the tunnel to be excavated. 1.5 times the diameter of the tunnel to be excavated, the distance between adjacent monitoring sections is equal to the step distance. In this embodiment, the set distance is 10m.

Before step 3 of each step of the tunnel to be excavated, monitoring points and monitoring instruments need to be arranged on the existing operating tunnel.

The construction method of this embodiment, through the asymmetric grouting reinforcement in step 2, can effectively offset the spatial torsion effect on the existing operating tunnel during the construction of the tunnel to be excavated, and reduce the uneven settlement and uneven settlement of the existing operating tunnel. When the excavation groove and core soil are excavated at the same time, the cutting and grinding excavation method is adopted. Compared with the traditional drilling and blasting method, the disturbance of the surrounding rock during the excavation construction can be greatly reduced, effectively guaranteeing The mechanical properties of the surrounding rock meet the requirements of the existing operating tunnels for the bearing capacity of the surrounding rock.

Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the scope of protection of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to pay creative work. Various modifications or deformations that can be made are still within the protection scope of the present invention.

Claims (9)

1. a tunnel excavation construction method of obliquely passing through an existing operating tunnel with a minimum clear distance, is characterized in that, comprises the following steps: Step 1: Obtain the distribution of rock formations and the physical and mechanical parameters of surrounding rock within the influence area of the tunnel excavation in front of the tunnel face to be excavated by synthesizing the geological exploration data and the test results of advanced drilling and coring; Step 2: Within a step range along the axis of the tunnel to be excavated, perform asymmetric grouting reinforcement on the surrounding rock in front of the face of the tunnel to be excavated to improve the surrounding area of the overlapping area between the tunnel to be excavated and the existing operating tunnel. mechanical properties of rock; Step 3: Reserve core soil, excavate the rock mass in front of the face by cutting and grinding, and excavate trenches with a depth equal to the step distance set along the contour line of the tunnel edge to be excavated, and monitor existing operations during the excavation process. Tunnel support stress state and displacement; Step 4: Install the support structure in the excavation groove; Step 5: Excavate the reserved core soil by cutting and grinding, and monitor the support stress state and displacement of the existing operating tunnel during the excavation process; Step 6: According to the support stress state and displacement of the operating tunnel obtained in Step 3 and Step 5, the differential settlement of different positions on the same section of the existing operating tunnel is obtained; Step 7: grouting the surrounding rock below the area where the differential settlement value of the existing operating tunnel is greater than the set value, so that the differential settlement value of the area where the differential settlement value of the existing operating tunnel is greater than the set value is less than the set value; Step 8: Using the methods from Step 1 to Step 7, perform grouting and excavation work in multiple steps along the axis direction of the tunnel to be excavated in sequence until all grouting and excavation work is completed. 2. A kind of tunnel excavation construction method for obliquely passing through an existing operating tunnel with a minimal clear distance as claimed in claim 1, wherein in the step 2, the horizontal range of the surrounding rock reinforced by asymmetric grouting The inner area is the area where the projections of the tunnel to be excavated and the existing operating tunnel overlap in the horizontal plane, and the area within the vertical range is the area between the outline of the tunnel to be excavated and the outline of the existing operating tunnel. 3. A kind of tunnel excavation construction method for obliquely passing through an existing operating tunnel with a minimal clear distance as claimed in claim 1, characterized in that, in the step 2, the grouting material adopts cement single slurry, and the cement slurry The water-cement ratio ranges from 0.8 to 1. 4. a kind of tunnel excavation construction method for obliquely passing through existing operating tunnels under a very small clear distance as claimed in claim 1, it is characterized in that, in described step 3, the excavation method of excavation groove is: first in the The side wall of one side of the tunnel is cut and ground along the contour line to form the first excavation groove, then the second excavation groove is cut and ground along the contour line on the other side edge, and finally the third groove is cut and ground along the contour line of the tunnel vault. The excavation groove part, the first excavation groove part, the second excavation groove part and the third excavation groove part constitute the excavation groove part. 5. A kind of tunnel excavation construction method for obliquely passing through an existing operating tunnel with a minimal clear distance as claimed in claim 1, wherein in the step 5, the cutting and grinding motion trajectory of the reserved core soil is carried out. For the bottom-up S-shaped trajectory, the excavation depth of the core soil is equal to the step distance. 6. A kind of tunnel excavation construction method for obliquely passing through an existing operating tunnel with a very small clear distance as claimed in claim 1, characterized in that, before the step 3 is carried out, a plurality of monitoring devices are set in the existing operating tunnel The monitoring points are used to monitor the stress state and displacement of the support. The monitoring points are set on multiple monitoring sections in the set area of the existing operating tunnel, and each monitoring section is set with multiple monitoring points. The determination method of the area is as follows: determine the area corresponding to the face of the tunnel to be excavated in the existing operating tunnel, take this area as the center, and set the distance along the axis of the existing operating tunnel as the boundary of the set area. Between the two boundaries is the setting area. 7. The tunnel excavation construction method for obliquely penetrating an existing operating tunnel with a minimal clear distance as claimed in claim 6, wherein the set distance is 1.5 times the diameter of the tunnel to be excavated, and the adjacent The distance of the monitoring section is equal to the step distance. 8. A kind of tunnel excavation construction method for obliquely passing through an existing operating tunnel with a minimal clear distance as claimed in claim 6, characterized in that, in the same monitoring section, the vault position and the vault bottom of the existing operating tunnel One monitoring point is set at the position and the two arch waist positions, one monitoring point is inserted at equal intervals between the monitoring points of the vault and the two arch waists, and one monitoring point is inserted at equal intervals between the monitoring points of the arch bottom and the two arch waists. Monitoring points. 9. A kind of tunnel excavation construction method for obliquely passing through an existing operating tunnel with a minimal clear distance as claimed in claim 1, wherein in the step 7, the grouting material adopts cement single slurry, and the cement slurry The water-cement ratio ranges from 0.8 to 1.