A construction technology for expanding excavation of a long-span tunnel

Abstract

The present invention relates to a construction technology for enlarging the excavation of a long-span tunnel, belonging to the technical field of tunnel construction, and includes the following steps: Step 1: Backfill sandbags at the lower part of the main tunnel of the tunnel part to be enlarged to form a step, and mark a number of demolition points on the inner surface of the secondary lining of the enlarged part; Step 2: Insert the main grouting pipe into the outside of the secondary lining of the enlarged part for grouting; Step 3: Insert a number of auxiliary grouting pipes along the demolition points of the secondary lining to the outside of the secondary lining for grouting, and at the same time, conduct preliminary excavation of the secondary lining at the demolition points; Step 4: Start from the demolition points, demolish the secondary lining of the upper bench, and enlarge the excavation according to the inner contour of the target structure, and apply the primary support after the enlargement is completed; Step 5: Start from the demolition points, demolish the secondary lining of the lower bench, and enlarge the excavation according to the inner contour of the target structure, and apply the primary support after the enlargement is completed; while improving the construction efficiency, it takes into account the construction safety.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and particularly relates to a construction technology for expanding and excavating a large-span tunnel. Background Art

[0002] With the economic development, there is a probability that the existing traffic infrastructure will face the problem of insufficient capacity and needs to be expanded. For example, when the number of lanes of a tunnel facility is small and new structures such as emergency parking bays need to be expanded, the tunnel needs to be expanded and excavated.

[0003] Due to the particularity of the geological structure deep in the tunnel, when constructing the existing structure of the tunnel, the existing structure needs to be demolished and re-excavated. During the excavation process, the surrounding geological environment will be affected, and the demolition of the existing structure will lead to a decrease in the supporting capacity. Under the combined action of the two, there is a probability of causing the collapse of the existing structure. For this reason, Chinese Patent CN110593909A discloses a construction method for replacing the secondary lining of a tunnel, including: performing sleeve lining reinforcement on the secondary lining to be replaced; setting an isolation and shock absorption groove at the junction of the demolished and non-demolished parts; constructing an isolation groove in the demolition area and the reserved area before demolishing the secondary lining to cut off all the secondary lining concrete and steel bars; performing radial grouting reinforcement on the surrounding rock behind the arch wall before demolishing the lining; demolishing the secondary lining, demolishing the reinforced sleeve arch, and retaining the primary support; if the thickness of the secondary lining is less than 2 / 3 of the original design, replacing the primary support, demolishing and expanding the original primary support in three steps, and then restoring the secondary lining. After the replacement length of the secondary lining or the primary support reaches 12m, the secondary lining concrete is timely re-constructed, and the secondary lining is constructed in groups of 10.5m / 1; if the thickness of the secondary lining is greater than 2 / 3 of the original design, directly restore the secondary lining; it solves the problem of high safety risk in the construction of replacing the secondary lining of the tunnel by performing radial grouting reinforcement on the surrounding rock behind the arch wall before demolishing the lining; however, in the above solution, it is necessary to grout around the secondary lining first and then demolish the secondary lining. At this time, grouting and demolition need to be carried out in two steps successively, and the construction efficiency is low. For this reason, a construction technology for expanding and excavating a large-span tunnel that improves the construction efficiency while taking into account the construction safety is needed. Summary of the Invention

[0004] To solve the above problems existing in the prior art, the invention provides a construction technology for expanding and excavating a large-span tunnel, which has the characteristics of improving the construction efficiency while taking into account the construction safety.

[0005] The object of the invention can be achieved by the following technical solutions:

[0006] A construction technology for expanding and excavating a large-span tunnel includes the following steps:

[0007] Step 1: Backfill sandbags at the lower part of the main tunnel of the part of the tunnel to be expanded and excavated to form a step, and mark a number of demolition points on the inner surface of the secondary lining of the expanded and excavated part;

[0008] Step 2: Insert the main grouting pipe into the outside of the secondary lining of the enlarged excavation part for grouting;

[0009] Step 3: Insert several auxiliary grouting pipes along the breaking point of the secondary lining to the outside of the secondary lining for grouting, and at the same time, conduct preliminary excavation of the secondary lining at the breaking point;

[0010] Step 4: Starting from the breaking point, conduct the breaking of the secondary lining of the upper bench, and enlarge the excavation according to the inner contour of the target structure. After the enlargement excavation is completed, apply the initial support;

[0011] Step 5: Starting from the breaking point, conduct the breaking of the secondary lining of the lower bench, and enlarge the excavation according to the inner contour of the target structure. After the enlargement excavation is completed, apply the initial support.

[0012] As a preferred technical solution of the present invention, the Step 3 further includes: pulling out the auxiliary grouting pipe before the end of grouting.

[0013] As a preferred technical solution of the present invention, the Step 1 further includes: measuring the span L of the enlarged tunnel part; the Step 3 further includes: Step 3: Insert the auxiliary grouting pipe into the breaking point of the secondary lining and insert it to the outside of the secondary lining for grouting, and adjust the grouting volume to G, G = L / L0×G0, where L0 and G0 are pre-calculated constants.

[0014] As a preferred technical solution of the present invention, the Step 3 further includes: applying a vibrator outside the auxiliary grouting pipe and applying vibration to the auxiliary grouting pipe during the grouting process of the auxiliary grouting pipe.

[0015] As a preferred technical solution of the present invention, the Step 3 further includes: increasing the power of the vibrator when the span of the enlarged tunnel part exceeds the threshold, and reducing the power of the vibrator when the span of the enlarged tunnel part is lower than the threshold;

[0016] As a preferred technical solution of the present invention, the Step 3 further includes: adjusting the power of the vibrator to p, where p = f(L)×p0, f(L) = Log(1.8x - 0.8) + 1.1, x = L / L0, 0.5L0≤L≤1.5L0;

[0017] As a preferred technical solution of the present invention, the Step 4 further includes: setting the number of breaking points a for one-time breaking before breaking, where a = L0 / L×a0;

[0018] As a preferred technical solution of the present invention,

[0019] The beneficial effects of the present invention are:

[0020] (1) By dividing a number of demolition points at the secondary lining, drilling holes at the demolition points, inserting auxiliary grouting pipes and then grouting at the demolition points, under the combined action of the drilling at the demolition points and the pressure exerted by the grouting on the secondary lining, the structural strength is weakened, and the soil layer near the demolition points of the secondary lining is grouted to additionally reinforce the soil layer near the demolition points. At the same time, during the grouting process, the secondary lining structure near the demolition points is further demolished, further weakening the structural strength near the demolition points of the secondary lining, reducing the construction time spent on subsequent demolition of the secondary lining, improving the construction efficiency, and taking into account the construction safety at the same time;

[0021] (2) By adjusting the auxiliary grouting supply according to the span data to control the grouting volume outside the secondary lining, when the tunnel span is large, the bearing capacity of the soil layer is poor, and the area of the secondary lining is large, the grouting volume outside the secondary lining is increased to achieve more sufficient grouting at the vault to reinforce the soil layer, and at the same time, the extrusion force of the cement slurry on the secondary lining is more fully utilized to achieve pre-demolition of the secondary lining; when the tunnel span is small, the grouting volume outside the secondary lining is reduced to ensure the construction efficiency;

[0022] (3) By vibrating the auxiliary grouting pipe with a vibrator and transmitting the vibration to the demolition points of the secondary lining, the structural strength of the demolition points is further reduced, the construction time spent on subsequent demolition of the secondary lining is reduced, and the construction efficiency is improved. At the same time, the vibration improves the density and uniformity of the cement slurry in the auxiliary grouting pipe, improves the grouting effect, and ensures safety;

[0023] (4) By adjusting the vibrator power according to the tunnel span, when the span is high and a higher vibration power is required to assist in the formation of the slurry in the grouting pipe or to more fully pre-demolish the secondary lining, the vibration power is increased to assist in the densification of the slurry and more fully pre-demolish the secondary lining. When the power span is low and a higher vibration power is not required to assist in the formation of the slurry in the grouting pipe or to fully pre-demolish the secondary lining, the vibration power is reduced to save energy consumption. Description of the Drawings

[0024] For the convenience of those skilled in the art to understand, the present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 It is a schematic structural diagram of the tunnel after the sandbag backfill of the present invention;

[0026] Figure 2 It is a schematic structural diagram during the grouting process of the present invention;

[0027] Main Component Symbol Description:

[0028] In the figure: 1, tunnel; 11, secondary lining; 2, main grouting pipe; 21, auxiliary grouting pipe; 3, sandbag. Detailed Embodiments

[0029] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following specifically describes in detail the specific implementation manner, structure, features and their effects of the present invention in combination with the accompanying drawings and preferred embodiments.

[0030] Please refer to Figure 1-2 , a construction technology for expanding and excavating a large-span tunnel, including the following steps:

[0031] Step 1: Backfill sandbags 3 at the lower part of the main tunnel of the part of the tunnel 1 that needs to be expanded and excavated to form a step, and mark a number of demolition points on the inner surface of the secondary lining 11 of the expanded and excavated part;

[0032] Specifically, in this solution, the tunnel 1 is a single-hole four-lane tunnel 1 with a clear width of the building limit of 18.25 m and a clear height of the limit of 5.0 m;

[0033] In this solution, the expansion and excavation is constructed by the bench method. Since the expansion and excavation construction is carried out on the basis of the existing tunnel 1, it is impossible to first excavate the soil in the upper part of the target position of the tunnel 1 to form a step like the traditional tunnel 1 excavation method. Therefore, first determine the main tunnel part of the existing tunnel 1 that needs to be expanded and excavated, and backfill sandbags 3 at the lower part of the main tunnel of the existing tunnel 1 until the sandbags 3 form a platform close to half of the inner height of the main tunnel. At this time, the plane composed of the ground of the main tunnel of the existing tunnel 1 and the sandbags 3 forms two steps. The plane composed of the sandbags 3 is the upper step, and the ground of the main tunnel of the existing tunnel 1 is the lower step;

[0034] Subsequently, since it is necessary to demolish the secondary lining 11 of the existing tunnel 1 during the expansion and excavation construction in order to excavate the soil layer outside the secondary lining 11, for this reason, the operators mark a number of demolition points on the inner surface of the secondary lining 11 with tools such as paint according to the construction plan to indicate the starting position of the demolition during the subsequent demolition;

[0035] After Step 1 is completed, Step 2 is executed:

[0036] Since before the demolition, the force of the demolition of the secondary lining 11 will be transmitted to the soil layer structure outside the secondary lining 11, and the existing secondary lining 11 structure will cause the support capacity to decrease. Under the combined action of the two, there is a probability of causing the collapse of the existing structure. To avoid such a situation, in Step 2, the main grouting pipe 2 is inserted into the outside of the secondary lining 11 of the expanded and excavated part for grouting;

[0037] Specifically, the outside of the secondary lining 11 of the expanded and excavated part refers to the rock and soil layer on the side of the secondary lining 11 of the expanded section of the existing tunnel 1 away from the tunnel 1. During grouting, a φ42 small catheter with a length of 3.5 m is used for radial support and cement slurry is injected. The small catheters are arranged in a plum blossom shape with a spacing of 1 m × 1 m. The water-cement ratio of the cement slurry is 1:1, and the grouting pressure is 0.5 - 1.0 MPa. After the grouting is completed, the grouting effect is inspected by sampling;

[0038] After completing step 2, proceed to step 3:

[0039] In a general scheme, it is necessary to first grout around the secondary lining 11, and then to demolish the secondary lining 11. At this time, the grouting and demolishing need to be performed in two steps in sequence, and the construction efficiency is low. In the grouting process, the secondary lining 11 can be initially demolished by penetrating the grouting pipe. For this purpose, step three: a plurality of auxiliary grouting pipes 21 are inserted along the demolishing point of the secondary lining 11 to the outside of the secondary lining 11 to perform grouting, and at the same time, the secondary lining 11 is initially excavated at the demolishing point;

[0040] Specifically, the operator first drills holes in the secondary lining 11 at several demolition points of the secondary lining 11, so that the holes penetrate into the rock layer and soil layer to be grouted, and then inserts the auxiliary grouting pipes 21 along the several holes, and then the auxiliary grouting pipes 21 grout the soil layer;

[0041] The auxiliary grouting pipe 21 includes an upper pipe and a lower pipe, each of which has an outlet. The upper pipe and the lower pipe are arranged in such a way as to ensure that when the auxiliary grouting pipe 21 is inserted into the borehole, the upper pipe faces away from the secondary lining 11, and the lower pipe faces the secondary lining 11;

[0042] When in use, after the auxiliary grouting pipe 21 is inserted, cement slurry is sprayed out from the upper pipe and the lower pipe at the same time, poured into the soil layer outside the secondary lining 11, and the grouting in the soil layer outside the secondary lining 11 is completed. At the same time, cement slurry is continuously sprayed toward the lower pipe of the secondary lining 11. After the cement slurry fills the gaps in the soil layer, it continuously applies pressure to the surrounding structure under the action of hydraulic pressure. This part of the pressure forms a force acting on the demolition point of the secondary lining 11 from the outside of the secondary lining 11. Since the demolition point has been drilled, a structural weakness is formed. At this time, under the action of grouting, the structural strength of the secondary lining 11 near the demolition point is weakened, and the grouting of the soil layer and the rock layer is completed at the same time, and the pre-demolition of the secondary lining 11 is achieved, which reduces the construction time cost of the subsequent demolition of the secondary lining 11 and improves the construction efficiency.

[0043] At the same time, since the secondary lining 11 is initially demolished and the secondary lining 11 plays a partial role in bearing the surrounding soil layers, during the demolition process, the bearing capacity of the surrounding soil layers near the demolition point of the secondary lining 11 decreases. At this time, the auxiliary grouting pipe 21 for grouting at the demolition point performs additional grouting on the soil layers near the demolition point, thereby improving the strength of the soil layers near the demolition point and reducing the probability of the soil layers near the demolition point collapsing into the tunnel 1, thereby reducing the probability of soil layer collapse caused by the reduction of the structural strength of the demolition point of the secondary lining 11;

[0044] During the above process, the operator simultaneously conducts preliminary excavation on the secondary lining 11 around the demolition point, drills holes with a depth of 10 - 50 cm around the demolition point using a drill rig, or shallowly demolishes the secondary lining 11 around the demolition point using a hydraulic hammer, further reducing the structural strength of the secondary lining 11 near the demolition point, achieving pre-demolition of the secondary lining 11, reducing the construction time spent on subsequent demolition of the secondary lining 11, and improving construction efficiency;

[0045] By dividing several demolition points at the secondary lining 11, drilling holes at the demolition points, inserting auxiliary grouting pipes 21, and then grouting at the demolition points, under the combined action of the holes drilled at the demolition points and the pressure exerted by the grouting on the secondary lining 11, the structural strength is weakened, and grouting is completed in the soil layer near the demolition points of the secondary lining 11, additionally reinforcing the soil layer near the demolition points. At the same time, during the grouting process, the structure of the secondary lining 11 near the demolition points is further demolished, further weakening the structural strength near the demolition points of the secondary lining 11, reducing the construction time spent on subsequent demolition of the secondary lining 11, improving construction efficiency, and taking into account construction safety;

[0046] After step three is completed, step four and step five are executed;

[0047] Step four: Starting from the demolition point, demolish the secondary lining 11 of the upper bench and excavate according to the inner contour of the target structure. After the excavation is completed, apply the primary support;

[0048] Specifically, define the secondary lining 11 structure at and above the upper bench height as the upper part. Starting from the arch crown of the existing tunnel 1, segmentally demolish the upper secondary lining 11 structure from top to bottom in the direction of the strong side. After the demolition is completed, excavate the tunnel 1 of the upper bench part according to the expanded target shape. At the same time, execute step five. Starting from the demolition point, demolish the secondary lining 11 of the upper bench and excavate according to the inner contour of the target structure. After the excavation is completed, apply the primary support; The execution order of step four and step five refers to the existing tunnel 1 bench construction method.

[0049] Optionally, in step three, before the grouting ends, pull out the auxiliary grouting pipe 21. After pulling out the auxiliary grouting pipe 21, a structural cavity is formed at the drilled hole of the demolition point, and at this time, there is no filling of the auxiliary grouting pipe 21 at the drilled hole, and the structural strength at the demolition point further decreases, resulting in further reduction of the construction time spent on subsequent demolition of the secondary lining 11 and improvement of construction efficiency.

[0050] During the process of inserting the above-mentioned auxiliary grouting pipe 21 into the secondary lining 11 along the demolition point for grouting, for tunnels 1 with different spans, when the span of the tunnel 1 is small, the total area of the secondary lining 11 is small, and the time consumed for demolition is short. For the vault part of the tunnel 1 with a small span, the distance from the side wall is relatively close. At this time, the existing structure of the tunnel 1 can bear more of the pressure of the outer soil layer during demolition, and there is no need to make excessive use of the extrusion effect of the cement slurry to pre-demolish the secondary lining 11, reducing the duration of the grouting link and ensuring the construction efficiency. Therefore, for tunnels 1 with a small span, in the grouting steps of steps two and three, there is no need for overly sufficient grouting to reinforce the soil layer;

[0051] For tunnels 1 with a large span, the total area of the secondary lining 11 is large, and the time consumed for demolition is long. The distance from the vault part to the side wall is far. At this time, the existing structure of the tunnel 1 cannot bear the pressure of the outer soil layer to a large extent during demolition. Therefore, for tunnels 1 with a large span, in the grouting steps of steps two and three, relatively sufficient grouting is required to reinforce the soil layer, and at the same time, the extrusion force of the cement slurry on the secondary lining 11 needs to be more fully utilized to achieve the pre-demolition of the secondary lining 11; for this purpose, in step one, the span L of the excavated part of the tunnel 1 is measured; at the same time, step three also includes: inserting the auxiliary grouting pipe 21 into the demolition point of the secondary lining 11 and inserting it outside the secondary lining 11 for grouting, and adjusting the grouting volume to G, G = L / L0 × G0, where L0 and G0 are pre-calculated constants;

[0052] When the measured span value L is large, relatively sufficient grouting is required to reinforce the soil layer, and at the same time, the extrusion force of the cement slurry on the secondary lining 11 needs to be more fully utilized to achieve the pre-demolition of the secondary lining 11. At this time, the value of G = L / L0 × G0 is large. When the grouting volume for grouting is adjusted to G, the grouting volume of the soil layer outside the secondary lining 11 is increased when the span of the tunnel 1 is large; similarly, when the measured span value L is small, there is no need for overly sufficient grouting to reinforce the soil layer, reducing the duration of the grouting link, and there is no need to make excessive use of the extrusion effect of the cement slurry to pre-demolish the secondary lining 11. At this time, the value of G = L / L0 × G0 is small. When the grouting volume for grouting is adjusted to G, the grouting volume of the soil layer outside the secondary lining 11 is reduced when the span of the tunnel 1 is small;

[0053] By adjusting the auxiliary grouting according to the span data to control the grouting volume outside the secondary lining 11, when the span of the tunnel 1 is large, the soil layer has poor bearing capacity, and the area of the secondary lining 11 is large, the grouting volume of the soil layer outside the secondary lining 11 is increased, achieving relatively sufficient grouting of the vault to reinforce the soil layer, and at the same time, more fully utilizing the extrusion force of the cement slurry on the secondary lining 11 to achieve the pre-demolition of the secondary lining 11; when the span of the tunnel 1 is small, the grouting volume of the soil layer outside the secondary lining 11 is reduced, taking into account the construction efficiency.

[0054] To further improve the pre-breaking effect of the auxiliary grouting pipe 21 on the secondary lining 11, step three further includes: applying a vibrator outside the auxiliary grouting pipe 21 and applying vibration to the auxiliary grouting pipe 21 during the grouting process. In this embodiment, a vibrator is provided outside each auxiliary grouting pipe 21. When the auxiliary grouting pipe 21 is grouting, the vibration is transmitted to the breaking point of the secondary lining 11 through the auxiliary grouting pipe 21, further reducing the structural strength of the breaking point, reducing the construction time spent on the subsequent breaking of the secondary lining 11, improving the construction efficiency. At the same time, the vibration improves the density and uniformity of the cement slurry in the auxiliary grouting pipe 21, improves the grouting effect, and ensures safety.

[0055] Since when the span of the tunnel 1 is small, the existing structure of the tunnel 1 can bear more of the pressure of the outer soil layer during breaking, without excessive reinforcement and without excessive pre-breaking of the secondary lining 11, thus saving construction energy consumption. When the span of the tunnel 1 is large, more sufficient soil reinforcement is required, and at the same time, more sufficient pre-breaking of the secondary lining 11 is needed; for this reason, in the above step three: when the span of the excavated part of the tunnel 1 exceeds the threshold, the power of the vibrator is increased, and when the span of the excavated part of the tunnel 1 is lower than the threshold, the power of the vibrator is decreased;

[0056] Specifically, the power of the vibrator is p, where p = f(L) × p0, f(L) = Log(1.8x - 0.8) + 1.1, x = L / L0, 0.5L0 ≤ L ≤ 1.5L0. When L is less than 0.5L0 or greater than 1.5L0, take L = 0.5L0 or L = 1.5L0;

[0057] When the value of L is low, there is no need for too high vibration power to assist in the formation of the slurry in the auxiliary grouting pipe 21 or to pre-break the secondary lining 11. At this time, the value of f(L) = Log(1.8x - 0.8) + 1.1 is low, and the value of p = f(L) × p0 is low. When the power of the vibrator is adjusted to p, the power of the vibrator is reduced when the span is low; when the value of L is high, a higher vibration power is required to assist in the formation of the slurry in the auxiliary grouting pipe 21 or to pre-break the secondary lining 11. At this time, the value of f(L) = Log(1.8x - 0.8) + 1.1 is low, and the value of p = f(L) × p0 is low. When the power of the vibrator is adjusted to p, the power of the vibrator is reduced when the span is low;

[0058] By adjusting the power of the vibrator according to the span of the tunnel 1, when the span is high and a higher vibration power is required to assist in the formation of the slurry in the auxiliary grouting pipe 21 or to perform more sufficient pre-breaking of the secondary lining 11, the vibration power is increased, thereby assisting in the densification of the slurry and performing more sufficient pre-breaking of the secondary lining 11. When the power span is low and there is no need for a higher vibration power to assist in the formation of the slurry in the auxiliary grouting pipe 21 or to perform sufficient pre-breaking of the secondary lining 11, the vibration power is reduced, thereby saving energy consumption.

[0059] Since during demolition, removing too much of the secondary lining 11 at once, especially the secondary lining 11 in the upper bench part, has a probability of drastically changing the load-bearing capacity of the tunnel 1 on the soil layer and increasing the probability of the tunnel 1 collapsing, it is necessary to demolish the secondary lining 11 in segments or batches. For this reason, step four further includes: before demolition, setting the number of demolition points a for a single demolition batch, and demolishing the demolition points of the part of the tunnel 1 that needs to be enlarged in batches, where a = L0 / L × a0;

[0060] Specifically, several demolition points in a single demolition batch are close to each other, several demolition points in a single demolition batch form a rectangular array, and the rectangular array formed by several demolition points in a single demolition batch does not contain demolition points of other batches;

[0061] When the value of L is relatively high, it represents a relatively large span. At this time, the redundancy of the load-bearing capacity of the tunnel 1 on the soil layer is relatively low, and it is necessary to reduce the area of the secondary lining 11 demolished at one time. At this time, the value of a = L0 / L × a0 is relatively low. When setting the number of demolition points for a single demolition batch to a, the area of the secondary lining 11 demolished in a single batch is reduced, thereby reducing the probability of collapse and improving safety. When the value of L is relatively low, it represents a relatively small span. At this time, the redundancy of the load-bearing capacity of the tunnel 1 on the soil layer is relatively high, and it is possible to appropriately increase the area of the secondary lining 11 demolished in a single batch. When setting the number of demolition points for a single demolition batch to a, the area of the secondary lining 11 demolished in a single batch is increased, thereby improving the construction efficiency.

[0062] By setting the number of demolition points for a single demolition batch to be negatively correlated with the span, when the span is relatively large, the area of the secondary lining 11 demolished in a single batch is reduced, thereby reducing the probability of collapse and improving safety. When the span is relatively small, the area of the secondary lining 11 demolished in a single batch is increased, thereby improving the construction efficiency.

[0063] The above is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to form an equivalent embodiment with equivalent changes, but as long as it does not depart from the technical content of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A construction technology for enlarging and excavating a long-span tunnel, characterized in that: It includes the following steps: Step 1: Backfill sandbags at the lower part of the main tunnel of the tunnel section to be enlarged and excavated to form a step, and mark several demolition points on the inner surface of the secondary lining of the enlarged and excavated part; Step 2: Insert the main grouting pipe into the outside of the secondary lining of the enlarged and excavated part for grouting; Step 3: Insert several auxiliary grouting pipes along the demolition points of the secondary lining to the outside of the secondary lining for grouting, and at the same time, conduct preliminary excavation of the secondary lining at the demolition points; Step 4: Start from the demolition points, demolish the secondary lining of the upper bench, and enlarge and excavate according to the inner contour of the target structure. After the enlargement and excavation are completed, apply the initial support; Step 5: Start from the demolition points, demolish the secondary lining of the lower bench, and enlarge and excavate according to the inner contour of the target structure. After the enlargement and excavation are completed, apply the initial support; The said Step 3 further includes: Before the grouting ends, pull out the auxiliary grouting pipes; The said Step 1 further includes: Measure the span L of the tunnel section to be enlarged and excavated; The said Step 3 further includes: Step 3: Insert the auxiliary grouting pipes into the demolition points of the secondary lining and insert them to the outside of the secondary lining for grouting, and adjust the grouting volume to G, where G = L / L0×G0, and L0 and G0 are pre-calculated constants; The said Step 3 further includes: Apply a vibrator outside the auxiliary grouting pipes and apply vibration to the auxiliary grouting pipes during the grouting process of the auxiliary grouting pipes.

2. The large-span tunnel excavation construction process according to claim 1, characterized in that: The said Step 3 further includes: Increase the power of the vibrator when the span of the tunnel section to be enlarged and excavated exceeds the threshold, and decrease the power of the vibrator when the span of the tunnel section to be enlarged and excavated is lower than the threshold.

3. The large-span tunnel excavation construction process according to claim 1, characterized in that: The said Step 3 further includes: Adjust the power of the vibrator to p, where p = f(L)×p0, f(L)=Log(1.8x - 0.8)+1.1, x = L / L0, 0.5L0≤L≤1.5L0.

4. A large-span tunnel excavation construction process according to claim 3, characterized in that: The said Step 4 further includes: Before the demolition, set the number of demolition points a for a single demolition batch, and demolish the demolition points of the tunnel section to be enlarged and excavated in batches, where a = L0 / L×a0.

Images