Excavation supporting method suitable for unfavorable geological tunnel

Abstract

The invention discloses an excavation and support method suitable for an unfavorable geological tunnel. The excavation and support method suitable for the unfavorable geological tunnel comprises the following steps: surveying and setting out; excavating a tunnel; performing trimming operation; performing deslagging operation; measuring and checking; performing primary supporting operation; the trimming operation comprises the following steps that S100, point cloud data of a tunnel section are obtained through scanning equipment; s200, based on the point cloud data, determining an actually measured section line corresponding to the point cloud data through a convex hull extraction algorithm; s300, determining an over-break and under-break detection result based on the actually measured section line; and S400, contour surface trimming operation is carried out based on the back break detection result. According to the excavation supporting method suitable for the unfavorable geological tunnel, the reliable and perfect tunnel excavation supporting method is provided for unfavorable geological tunnel construction, the stability is good, the technology is simple and practical, the good supporting effect can be provided, and meanwhile the construction cost is effectively controlled.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to an excavation and support method suitable for tunnels with poor geology. Background Art

[0002] Tunnel engineering plays a vital role in water conservancy projects, transportation projects and modern urban underground engineering construction. In order to achieve efficient and safe tunnel construction, mechanized construction has become a widely used method.

[0003] When constructing tunnels in poor geology, for large cantilever tunnel boring machines, in order to ensure construction efficiency, the tunnel boring machine head is relatively large in size. However, when the tunnel cross-section is small, the working space is small, which is not conducive to personnel operation. In addition, the large-sized tunnel boring machine head will generate a lot of dust during the tunneling process, which affects the personnel's line of sight and further increases the difficulty of tunneling, resulting in over-excavation and under-excavation during tunnel construction.

[0004] In addition, when constructing in areas with poor geological conditions, the surrounding rock of the tunnel is relatively soft, and it is difficult for the tunnel boring machine to accurately control the excavation contour line. Over-excavation and under-excavation are easy to occur during the construction process, resulting in the formation of irregular cross-sections. Summary of the invention

[0005] The technical problem to be solved by the present invention is that over-excavation and under-excavation are prone to occur in tunnels constructed in areas with poor geology. The purpose is to provide an excavation and support method suitable for tunnels with poor geology to solve the above-mentioned problem.

[0006] The present invention is achieved through the following technical solutions:

[0007] An excavation and support method suitable for tunnels with poor geology, comprising the following steps: surveying and setting out; tunnel excavation; trimming; slag removal; surveying and verification; initial support;

[0008] Among them, the trimming operation includes the following steps:

[0009] S100: Obtain point cloud data of the tunnel section through scanning equipment;

[0010] S200: Based on the point cloud data, determine the measured section line corresponding to the point cloud data by using a convex hull extraction algorithm;

[0011] S300: determining an over-break and under-break detection result based on the measured cross-section line;

[0012] S400: Perform contour surface trimming operations based on the over-break and under-break detection results.

[0013] In one possible design, S200 includes the following steps:

[0014] S210 selects a reference point P0;

[0015] S220 polar angle sorting: calculate the remaining points P i (i=1,2,…,n-1) Polar angle θ relative to reference point P0 i , sort the remaining points in order from small to large polar angles;

[0016] S230 Construct convex hull: determine the remaining points P i The corresponding convex hull.

[0017] In one possible design, S230 includes the following steps:

[0018] S231: Initialize a stack S and push P0 and P1 into the stack;

[0019] S232: Based on the stack S, obtain the two points S at the top of the stack top-1 and S top , form a vector with the two top points of the stack and the current point P2 and obtain the cross product of the vector;

[0020] S233: Change different stack vertices until the cross product of the vectors is greater than 0, and push P2 into stack S;

[0021] S234: Repeat S232 and S233 until each subsequent point P i (i=3,4,···,n-1) is pushed into stack S.

[0022] In a possible design, in S210, the bottom point is used as the reference point P0; if there are multiple bottom points, the point on the leftmost side is selected as the reference point P0.

[0023] In one possible design, in S220, the polar angle θ is calculated based on the following formula: i :

[0024]

[0025] In the formula,

[0026] In a possible design, the surveying and setting out includes the following steps: advance geological forecasting to ascertain the geological conditions; and setting out the axis and building contours according to the tunnel centerline, contour line, stake number, slope ratio, and elevation.

[0027] In one possible design, tunnel excavation includes the following steps:

[0028] Excavation of lower steps: excavate the left and right arch feet of the lower steps; excavate the main body in the middle of the lower steps;

[0029] Excavation of the middle step: excavate the left and right arch feet of the middle step; excavate the middle body of the middle step;

[0030] Excavation of the upper step: excavate the left and right arch feet of the upper step; excavate the main body in the middle of the upper step.

[0031] In a possible design, the slag removal operation includes the following steps: after the excavation of the middle step is completed, the slag is removed for the first time; when the excavation operation of the upper step is carried out, the slag is removed for the second time simultaneously.

[0032] In a possible design, the measurement verification includes the following steps: based on the total station measurement, guiding the laser beam of the wireless laser layout device to transmit to the positioning contour line through the control device; marking the position of the side hole.

[0033] In one possible design, the initial support operation includes the following steps:

[0034] Use advance small conduit support and hollow grouting anchors along the tunnel side walls and arch top;

[0035] Set up arches;

[0036] The side walls and top arch are arranged with steel mesh and sprayed with reinforced concrete.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] The excavation and support method suitable for tunnels with poor geology provides a reliable and complete tunnel excavation and support method for tunnel construction with poor geology. It has good stability, simple and practical process, can provide better support effect, and effectively control construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0040] Figure 1 The figure is a flow chart of an excavation support method suitable for tunnels with poor geology. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0042] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known structures, circuits, materials, or methods are not specifically described.

[0043] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0044] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0045] Embodiment 1:

[0046] like Figure 1 As shown, an excavation support method suitable for tunnels with poor geological conditions includes the following steps:

[0047] S1 Surveying and staking out: Stake out the axis and building outline according to the tunnel centerline, contour line, pile number, slope ratio and elevation.

[0048] In tunnel construction, the centerline of the tunnel is the reference axis of the entire tunnel on the plane, which determines the direction of the tunnel. Using the centerline of the tunnel as a reference for layout can ensure that subsequent excavation and construction are carried out along the predetermined straight line direction, avoiding the situation where the tunnel deviates from the design route. The contour line clarifies the cross-sectional shape of the tunnel at different pile numbers and elevations. According to the contour line layout, the excavated tunnel section can meet the design requirements and ensure the accuracy of the spatial shape of the tunnel, such as the accurate formation of different design shapes such as circular and horseshoe shapes. The pile number is used to mark different positions of the tunnel along the centerline, similar to the mileage piles on the road. The slope ratio determines the change in the longitudinal slope of the tunnel, which has an important impact on drainage, construction and transportation. The elevation clarifies the position height of the tunnel in the vertical direction.

[0049] It is worth noting that, before setting out, it is preferred to conduct an advance geological forecast to ascertain the geological conditions. Based on this, more specific geological conditions can be obtained to adjust, improve and optimize the construction plan, improve the construction quality and ensure construction safety. Taking the construction of a water diversion tunnel as an example, the activity of groundwater can be ascertained through an advance geological forecast, and the leakage and pressure can be measured to prevent sudden water inrush.

[0050] S2 tunnel excavation;

[0051] In S2, mechanical excavation is preferred to speed up the construction, shorten the construction period and reduce the construction cost. It is easy to understand that at least one of mechanical excavation and manual excavation is selected during tunnel excavation.

[0052] Since the construction area has poor geology, the specific excavation plan was optimized. Specifically:

[0053] The excavation of S2 tunnel includes the following steps:

[0054] Excavation of S21 lower step: excavate the left and right arch feet of the lower step; excavate the main body in the middle of the lower step;

[0055] S22 middle step excavation: excavate the left and right arch feet of the middle step; excavate the middle body of the middle step;

[0056] Excavation of S23 upper step: excavate the left and right arch feet of the upper step; excavate the main body in the middle of the upper step.

[0057] Based on the above design scheme, and taking into account geotechnical mechanics and tunnel stability, excavating gradually from bottom to top can effectively reduce the disturbance to the upper rock and soil mass and maintain the overall stability of the tunnel during construction. Therefore, the lower step, middle step and upper step are excavated in sequence from bottom to top. The method of excavating the arch waist, arch crown and other parts step by step and layer by layer is also to evenly release the stress of the rock and soil mass, avoid large-scale excavation at one time, lead to stress concentration, and cause safety accidents such as landslides. By gradually advancing, the rock and soil mass has time to adjust its stress and adapt to the changes brought about by excavation, ensuring construction safety and excavation quality.

[0058] In addition, when excavating, the rock mass in the lower part of the section is removed first. When excavating the upper part, due to the deadweight of the rock mass, the rock mass can be removed more easily, thereby improving construction efficiency.

[0059] Furthermore, for the construction sequence in the same step, taking the lower step as an example, the left and right arch feet of the lower step are excavated first. This is because the arch feet are an important supporting part of the arch structure. Dealing with the arch feet first can provide a relatively stable foundation for the subsequent excavation of the middle main body and the upper step.

[0060] It is easy to understand that when the excavation area is close to the contour line, the excavation speed should be reduced, the excavation accuracy should be improved, and excessive over-excavation should be avoided.

[0061] S3 trimming operation;

[0062] Based on this, after S2 digs the tunnel, S3 is used to trim the edges to make the spatial shape of the tunnel accurate, avoid over-digging and under-digging, and ensure construction quality.

[0063] Specifically, the S3 trimming operation includes the following steps:

[0064] S100: Obtain point cloud data of the tunnel section through scanning equipment;

[0065] S200: Based on the point cloud data, determine the measured section line corresponding to the point cloud data by using a convex hull extraction algorithm;

[0066] S300: determining an over-break and under-break detection result based on the measured cross-section line;

[0067] S400: Perform contour surface trimming operations based on the over-break and under-break detection results.

[0068] Among them, in S100, laser scanning equipment or any other suitable type of equipment can be used to obtain tunnel section point cloud data. In S200, based on the construction plan, the thickness value and width value of the tunnel section are set, and the tunnel section point cloud is automatically segmented. The segmented section point cloud is projected onto the XOY plane, and then the section point cloud contour line is extracted to obtain the measured section line. In S300, the over-excavation result can be determined by comparing the measured contour line with the designed contour line. In S400, based on the over-excavation result, the excavation amount of the trimming operation is determined and the contour surface trimming is started to reduce the over-excavation and under-excavation. After the trimming is completed, the relevant operation equipment can be withdrawn.

[0069] It is worth noting that in S200, any suitable algorithm can be used to obtain the measured cross-section line. Here, the convex hull algorithm is used as an example for explanation:

[0070] S200 includes the following steps:

[0071] S210 selects reference point P0: the bottom point is taken as reference point P0 (i.e., the point with the smallest ordinate in the XOY plane); if there are multiple bottom points, the point on the leftmost side is selected as reference point P0 (i.e., the point with the smallest abscissa among the points with the smallest ordinate in the XOY plane);

[0072] S220 polar angle sorting: calculate the remaining points P i (i=1,2,…,n-1) Polar angle θ relative to reference point P0 i , sort the remaining points in order from small to large polar angles;

[0073] The polar angle θ is calculated based on the following formula: i :

[0074]

[0075] In the formula,

[0076] S230 Construct convex hull: determine the remaining points P i The corresponding convex hull;

[0077] Among them, S230 includes the following steps:

[0078] S231: Initialize a stack S and push P0 and P1 into the stack;

[0079] S232: Based on the stack S, obtain the two points S at the top of the stack top-1 and S top , form a vector with the two top points of the stack and the current point P2 and obtain the cross product of the vector;

[0080] S233: Change different stack vertices until the cross product of the vectors is greater than 0, and push P2 into stack S;

[0081] S234: Repeat S232 and S233 until each subsequent point P i (i=3,4,···,n-1) are pushed into stack s.

[0082] Based on this, the convex hull is obtained, and the points pushed into the stack are the points on the convex hull, which are also the points on the measured section line. Based on the convex hull, the distance between the convex hull and the designed contour and other parameters can be calculated to determine the over-excavation and under-excavation detection results.

[0083] S4 slag removal operation: the first slag removal is carried out after the excavation of the middle step is completed; the second slag removal is carried out simultaneously during the excavation of the upper step;

[0084] Based on this, after the excavation of the middle step is completed, a certain amount of slag has accumulated in the site. If it is not cleaned up in time, it will affect the subsequent excavation of the upper step and the operating space of the construction personnel, so the first slag cleaning is carried out. Before the first slag cleaning, the excavation equipment leaves the site to avoid mutual influence and interference between the excavation equipment and the slag cleaning equipment, ensure the safety of the slag cleaning operation, improve the efficiency of the first slag cleaning, and also protect the excavation equipment from damage.

[0085] After the first slag removal is completed, the excavation equipment will enter the site again and carry out the upper step excavation operation. At this time, the slag removal equipment will not leave the site and will start the second slag removal. Since the upper step excavation and slag removal operations can be carried out relatively independently in space, by carrying out these two tasks simultaneously, time can be fully utilized and the total construction time can be reduced.

[0086] For example, while the tunnel boring machine is excavating the upper steps, the slag cleaning equipment can be clearing the slag in the excavated area. The two do not interfere with each other, which improves construction efficiency.

[0087] S5 measurement verification: Based on total station measurement, the laser beam of the wireless laser layout device is guided by the control device to transmit to the positioning contour line; the side hole position is marked.

[0088] Among them, according to the location coordinates and other information obtained by the total station measurement, the wireless laser layout device is controlled by a control device, such as any suitable existing computer, and then the laser beam is guided to be projected to the contour line position that needs to be located in a predetermined direction and angle. This method utilizes the linear propagation characteristics of the laser and the high-precision measurement function of the total station to achieve accurate layout of the tunnel contour line.

[0089] At the same time, according to the construction plan, the position of the side holes is marked synchronously during the layout to guide the subsequent drilling operations. Specifically, after marking the position of the side holes that need to be calibrated, the tunneling equipment can perform drilling operations according to these marks, thereby ensuring that the position of the drilled holes is accurate and meets the design requirements. Based on this, during subsequent construction, such as when performing support operations such as anchor bolt installation, the accurate drilling position can ensure that the anchor bolt can effectively play its role in reinforcing the rock and soil around the tunnel.

[0090] S6 initial support operation: Use advance small duct support, hollow grouting anchor rods along the tunnel side walls and arch top; set up arch frames; arrange steel mesh on the side walls and top arch and spray reinforced concrete.

[0091] In S6, a pre-reinforced area is formed in the rock and soil in front of the tunnel excavation face through an advance small guide tube. That is, by injecting grout into the small guide tube, the slurry can fill the pores of the rock and soil, thereby improving the strength and stability of the rock and soil. At the same time, the small guide tube itself also plays a certain supporting role, preventing the collapse of the rock and soil in front during the excavation process, and providing safety protection for tunnel excavation in advance.

[0092] On the one hand, the hollow grouting anchor can inject grout into the interior, allowing the slurry to penetrate into the surrounding rock and soil, further improving the strength of the rock and soil; on the other hand, the anchor itself can anchor the rock and soil, connecting the rock and soil with supporting structures such as arches, thereby enhancing the integrity and stability of the entire support system.

[0093] The arch frame is set inside the tunnel and plays the role of the main supporting frame, bearing the pressure from the rock and soil and distributing it evenly.

[0094] The steel mesh arranged on the side walls and top arch can further improve the integrity of the support structure and prevent the partial fall of the rock and soil. The reinforced concrete of the spray cover can form a solid protective layer, which can not only resist the pressure of the rock and soil, but also prevent the erosion and damage of the internal structure of the tunnel by external factors such as groundwater and weathering, thus effectively protecting the safety and stability of the tunnel during construction and subsequent use.

[0095] Embodiment 2:

[0096] Based on Example 1, this embodiment takes a tunnel with a shallow burial depth, a surrounding rock mass with a broken zone and a weak structural surface, such as 61.7% of the surrounding rock is Class V surrounding rock, 38.3% is Class IV surrounding rock, and the burial depth of the tunnel is 13.0-27.8m, there are 2 cross trenches, and the surrounding rock mass has a broken zone and a weak structural surface as an example to further illustrate the excavation support method suitable for poor geological tunnels:

[0097] In S2, the mechanical excavation cycle advances 0.5 to 1m; a 1.8m thick material is reserved at the bottom of the tunnel for secondary excavation to form a slag loading platform and a staggered lane. The bottom is subsequently cleared and a trestle is used to ensure traffic, and the bottom steel arch frame and cushion layer are installed in sections of 5.5m-6.5m.

[0098] 3 to 5 meters of core soil is reserved at the top of the upper step, and excavation support is carried out at a staggered distance of about 2 to 4 meters on both sides of the middle. 2 meters is reserved on the lower step for secondary excavation.

[0099] In S6, a steel support and cushion concrete are poured at the bottom of the surrounding rock at one time, and a concrete cushion pavement with a segment length of not less than 6.0m is poured. A trestle with a length of not less than 12m is laid between the concrete cushion pavement and the upper part of the slag loading platform.

[0100] In the advanced small pipe support, the arch is set with an advanced small pipe in a range of not less than 120°. The length of the advanced small pipe is not less than 4.5m, and the row spacing of adjacent advanced small pipes is 2.5m-3.5m. The length of the hollow grouting anchor is 3.5m-4.5m, and the row spacing is 1m-1.5m. The thickness of the reinforced concrete sprayed on the steel mesh is not less than 50cm.

[0101] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An excavation support method suitable for tunnels with poor geology, characterized in that: The following steps are involved: Surveying and setting out; tunnel excavation; trimming operations; slag removal operations; Measurement and verification; initial support work; Among them, the trimming operation includes the following steps: S100: Obtain point cloud data of the tunnel section through scanning equipment; S200: Based on the point cloud data, determine the measured section line corresponding to the point cloud data by using a convex hull extraction algorithm; S300: determining an over-break and under-break detection result based on the measured cross-section line; S400: Perform contour surface trimming operations based on the over-break and under-break detection results.

2. The excavation support method for tunnels with poor geology according to claim 1 is characterized in that: S200 includes the following steps: S210 selects a reference point P0; S220 polar angle sorting: calculate the remaining points P i (i=1,2,…,n-1) Polar angle θ relative to reference point P0 i , sort the remaining points in order from small to large polar angles; S230 Construct convex hull: determine the remaining points P i The corresponding convex hull.

3. The excavation support method for tunnels with poor geology according to claim 2 is characterized in that: S230 includes the following steps: S231: Initialize a stack S and push P0 and P1 into the stack; S232: Based on the stack S, obtain the two points S at the top of the stack top-1 and S top , form a vector with the two top points of the stack and the current point P2 and obtain the cross product of the vector; S233: Change different stack vertices until the cross product of the vectors is greater than 0, and push P2 into stack S; S234: Repeat S232 and S233 until each subsequent point P i (i=3, 4, ..., n-1) are pushed into stack S.

4. The excavation support method for tunnels with poor geology according to claim 2 is characterized in that: In S210 , the bottom point is taken as the reference point P0 ; if there are multiple bottom points, the point on the leftmost side is selected as the reference point P0 .

5. The excavation support method for tunnels with poor geology according to claim 2 is characterized in that: In S220, the polar angle θ is calculated based on the following formula: i : In the formula, 6. The excavation support method for tunnels with poor geological conditions according to any one of claims 1 to 5, characterized in that: The surveying and setting out includes the following steps: advance geological forecast to ascertain the geological conditions; and setting out the axis and building outline according to the tunnel centerline, contour line, pile number, slope ratio and elevation.

7. The excavation support method for tunnels with poor geology according to any one of claims 1 to 5, characterized in that: Tunnel excavation includes the following steps: Excavation of lower steps: excavate the left and right arch feet of the lower steps; excavate the main body in the middle of the lower steps; Excavation of the middle step: excavate the left and right arch feet of the middle step; excavate the middle body of the middle step; Excavation of the upper step: excavate the left and right arch feet of the upper step; excavate the main body in the middle of the upper step.

8. The excavation support method for tunnels with poor geological conditions according to any one of claims 1 to 5, characterized in that: The slag removal operation includes the following steps: the first slag removal is carried out after the excavation of the middle step is completed; the second slag removal is carried out simultaneously during the excavation of the upper step.

9. The excavation support method for tunnels with poor geology according to any one of claims 1 to 5, characterized in that: The measurement verification includes the following steps: based on the total station measurement, the laser beam of the wireless laser layout device is guided to be transmitted to the positioning contour line through the control device; and the position of the side hole is marked.

10. The excavation support method for tunnels with poor geology according to any one of claims 1 to 5, characterized in that: The initial operation includes the following steps: Use advance small conduit support and hollow grouting anchors along the tunnel side walls and arch top; Set up arches; The side walls and top arch are arranged with steel mesh and sprayed with reinforced concrete.

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