Construction method of tunneling vertically under existing pipelines

Abstract

This invention discloses a construction method for a tunnel vertically passing under existing pipelines, comprising the following steps: grouting and reinforcing the geological body to be excavated to form a reinforced zone; vertically passing under the existing road in the vertical direction corresponding to the reinforced zone to form the exit section of the tunnel in the geological body to be excavated; using small guide pipes to pre-support the existing sewage pipes and existing rainwater pipes to form a support structure between the existing sewage pipes and existing rainwater pipes and the arch of the tunnel; continuing to excavate the geological body to be excavated along the exit section of the tunnel to form the tunnel below the existing road. This invention stabilizes the strata through full-section grouting, preventing water seepage at the tunnel face or loose fill at the arch causing tunnel face collapse and pipeline detachment. Furthermore, the pre-installation of small guide pipes below the pipelines to support the sewage and rainwater pipelines prevents pipeline detachment, avoiding adverse social impacts and thus preventing loss of benefits.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a construction method for excavating a tunnel vertically under an existing pipeline. Background Technology

[0002] Among related technologies, the cut-and-cover method is widely used in subway construction. When using the CRD (Cross-Diameter Relief) method to tunnel pipelines, it is essential to control the excavation sequence and take measures such as advanced small guide pipe support and full-section grouting protection to prevent pipeline damage.

[0003] However, when using the CRD (Cross-Diaphragm) method to pass under pipelines, there is a risk of pipeline leakage due to the close proximity of the arch to the sewage and rainwater pipelines. Furthermore, the complex geological conditions can easily cause pipeline damage and water leakage, leading to the risk of tunnel face collapse. Summary of the Invention

[0004] The main objective of this invention is to provide a construction method for vertically excavating tunnels to pass under existing pipelines. This method aims to solve the technical problems in the existing technology of using the CRD (Cross-Diaphragm Method) to pass under pipelines. Due to the close proximity of the arch to sewage and rainwater pipelines, there is a risk of pipeline leakage. Furthermore, the complex geological conditions can easily cause pipeline damage and water leakage, leading to the risk of tunnel face collapse.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a construction method for vertically excavating a tunnel under an existing pipeline, the method comprising:

[0007] Grouting is used to reinforce the excavated geological body, forming a reinforced zone;

[0008] Corresponding to the reinforcement area, a tunnel is vertically excavated under the existing road to form the exit section of the tunnel in the geological body to be excavated; wherein, an existing sewage pipe and an existing rainwater pipe are buried under the existing road, and the distance between the existing sewage pipe and the existing rainwater pipe and the arch of the tunnel in the vertical direction is 0.3m and 1m respectively, the diameter of the existing sewage pipe is greater than or equal to 600mm, and the diameter of the existing rainwater pipe is greater than or equal to 2000mm;

[0009] Small guide pipes are used to provide advance support for the existing sewage pipes and the existing rainwater pipes, so as to form a support structure between the existing sewage pipes and the existing rainwater pipes and the arch of the tunnel.

[0010] The excavation continues along the exit section of the tunnel, forming the tunnel beneath the existing road.

[0011] Optionally, in the above-mentioned construction method for vertically excavating a tunnel under an existing pipeline, the step of grouting and reinforcing the geological body to be excavated to form a reinforced zone includes:

[0012] Based on the preset drilling depth, preset drilling angle and preset grouting pressure, the geological body to be excavated is reinforced by cyclic grouting using a full-section grouting method to form the reinforced zone.

[0013] The reinforced area is located on the arch of the tunnel.

[0014] Optionally, in the above-mentioned method for constructing a tunnel vertically under an existing pipeline, the preset drilling depth is 10m, the preset drilling angle is α, 0°≤α≤45°, and the preset grouting pressure is P, 0.3Mpa≤P≤0.5Mpa.

[0015] Optionally, in the above-mentioned method for constructing a tunnel vertically under an existing pipeline, before the step of vertically under the existing road in the vertical direction corresponding to the reinforced area to form the exit section of the tunnel in the geological body to be excavated, the method further includes:

[0016] Obtain the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone;

[0017] Determine whether the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone meets the preset conditions;

[0018] If not, then secondary grouting reinforcement is carried out on the geological body to be excavated corresponding to the reinforcement zone until the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone meets the preset conditions.

[0019] Optionally, in the above-mentioned construction method for vertically crossing existing pipelines via a tunnel, the step of performing secondary grouting reinforcement on the geological body to be excavated corresponding to the reinforcement zone until the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone meets the preset conditions includes:

[0020] Set the grouting pressure to F1, and use the grouting pressure of F1 to perform secondary grouting reinforcement on the geological body to be excavated corresponding to the reinforcement zone;

[0021] During the secondary grouting reinforcement of the geological body to be excavated corresponding to the reinforcement zone, the value of the grouting pressure F1 is gradually changed to F2; wherein, 0 MPa ≤ F1 < 0.5 MPa, F1 < F2 ≤ 0.5 MPa.

[0022] Optionally, in the above-mentioned construction method for vertically tunneling under existing pipelines, before the step of using small guide pipes to provide advance support for the existing sewage pipe and the existing rainwater pipe to form a support structure between the existing sewage pipe and the existing rainwater pipe and the arch of the tunnel, the method further includes:

[0023] A pre-excavated small guide pipe is installed between the existing sewage pipe and the existing rainwater pipe and the arch of the underground tunnel using welded steel pipes.

[0024] Optionally, in the above-mentioned method for constructing a tunnel vertically under an existing pipeline, the step of continuing to excavate the geological body to be excavated along the exit section of the tunnel to form the tunnel below the existing road includes:

[0025] Continue excavating the geological body to be excavated along the exit section of the tunnel to form a tunnel to be supported;

[0026] Initial support is provided for the passage to be supported to form an initial support structure; wherein the initial support structure is housed in the passage to be supported, and one side of the initial support structure is against the geological body to be excavated in the passage to be supported.

[0027] The grouting pressure is set to F3, and the grouting pressure of F3 is used to backfill the geological body to be excavated covered by the initial support structure to form the tunnel under the existing road; wherein, 0.3Mpa≤F3≤0.5Mpa.

[0028] Optionally, in the above-mentioned construction method for vertically tunneling under existing pipelines, the step of using small guide pipes to provide advance support for the existing sewage pipe and the existing rainwater pipe, so as to form a support structure between the existing sewage pipe and the existing rainwater pipe and the arch of the tunnel, includes:

[0029] Using a water drill, holes are drilled circumferentially into the geological body to be excavated corresponding to the reinforced area on the arch of the tunnel, forming multiple installation positions;

[0030] Multiple small guide tubes are fabricated; wherein the number of small guide tubes is consistent with the number of mounting holes and is set in a one-to-one correspondence.

[0031] Each of the small guide tubes is inserted into the corresponding mounting hole;

[0032] The small conduits and the grid together form the support structure.

[0033] Optionally, in the above-mentioned method for constructing a tunnel vertically under an existing pipeline, the distance between two adjacent installation holes is 300mm, and each installation hole is distributed in a 140° curve in the geological body to be excavated corresponding to the reinforced area.

[0034] Optionally, in the above-mentioned construction method for vertically tunneling under existing pipelines using cut-and-cover tunnels, the step of fabricating multiple small guide pipes for steel pipes includes:

[0035] The front end of the steel pipe is cut into a pointed cone shape;

[0036] Multiple grout discharge holes are arranged in the middle of the steel pipe; wherein, the multiple grout discharge holes are distributed in a quincunx pattern, and the distance between two adjacent grout discharge holes is D, where 20cm≤D≤30cm;

[0037] The rear end of the steel pipe is used as the grout-stopping section;

[0038] Reinforcing steel hoops are welded to the tail end of each steel pipe to form the support structure together with the grid.

[0039] The above-described one or more technical solutions provided by this invention can have the following advantages or at least achieve the following technical effects:

[0040] This invention proposes a construction method for vertically tunneling existing pipelines through a cut-and-cover tunnel. The method stabilizes the strata by grouting the entire cross-section to prevent water seepage at the tunnel face or the collapse of the tunnel face due to loose fill at the arch, which could cause the pipeline to fall off. Furthermore, small pre-installed guide pipes are installed below the pipelines to support sewage and rainwater pipelines, preventing the pipelines from falling off and affecting the normal lives of residents, causing adverse social impacts, and thus preventing the loss of benefits. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the construction method for vertically excavating a tunnel to pass under an existing pipeline according to the present invention.

[0043] Figure 2 for Figure 1 A detailed flowchart preceding step S200;

[0044] Figure 3 for Figure 1Detailed flowchart of step S300;

[0045] Figure 4 for Figure 3 Detailed flowchart of step S320;

[0046] Figure 5 This is a schematic diagram of the structure of the excavation surface involved in the present invention;

[0047] Figure 6 This is a schematic diagram of the structure of the first guide hole involved in the present invention;

[0048] Figure 7 This is a schematic diagram of the structure of the second guide hole involved in the present invention;

[0049] Figure 8 This is a schematic diagram of the structure of the third guide tunnel involved in the present invention;

[0050] Figure 9 This is a schematic diagram of the structure of the fourth guide tunnel involved in the present invention;

[0051] Figure 10 This is a schematic diagram of the structure of the first temporary inverted arch, the second temporary inverted arch, the first intermediate partition wall, and the second intermediate partition wall involved in the present invention.

[0052] Explanation of icon numbers:

[0053]

[0054]

[0055] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0058] In this invention, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element. Furthermore, the meaning of "and / or" throughout the text includes three parallel options; for example, "A and / or B" includes option A, option B, or options where both A and B are satisfied.

[0059] In this invention, unless otherwise explicitly specified and limited, the terms "connection" and "fixed" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements.

[0060] In this invention, if there are descriptions involving "first," "second," etc., such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0061] In this invention, the use of suffixes such as "module," "component," "part," "unit," or "unit" to denote elements is solely for the purpose of illustrative purposes and has no specific meaning in itself. Therefore, "module," "part," or "unit" can be used interchangeably.

[0062] For those skilled in the art, the specific meanings of the above terms in this invention can be understood according to the specific circumstances. Furthermore, the technical solutions of the various embodiments can be combined with each other; however, this is based on the premise that those skilled in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0063] The inventive concept of the present invention will be further explained below with reference to some specific embodiments.

[0064] This invention proposes a construction method for vertically excavating tunnels to pass under existing pipelines.

[0065] Reference Figure 1 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 , Figure 1 This is a schematic diagram of the construction method for vertically excavating a tunnel to pass under an existing pipeline according to the present invention. Figure 5 This is a schematic diagram of the structure of the excavation surface involved in the present invention; Figure 6 This is a schematic diagram of the structure of the first guide hole involved in the present invention; Figure 7 This is a schematic diagram of the structure of the second guide hole involved in the present invention; Figure 8 This is a schematic diagram of the structure of the third guide tunnel involved in the present invention; Figure 9 This is a schematic diagram of the structure of the fourth guide tunnel involved in the present invention; Figure 10 This is a schematic diagram of the structure of the first temporary inverted arch, the second temporary inverted arch, the first intermediate partition wall, and the second intermediate partition wall involved in the present invention.

[0066] In one embodiment of the present invention, such as Figure 1 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 As shown, a construction method for excavating a tunnel vertically under an existing pipeline includes the following steps:

[0067] Step S100: Grouting is performed on the geological body to be excavated to reinforce it and form a reinforced zone;

[0068] Step S200: Corresponding to the reinforced area, vertically pass under the existing road in the vertical direction to form the exit section of the tunnel in the geological body to be excavated; wherein, an existing sewage pipe and an existing rainwater pipe are buried under the existing road, and the distance between the existing sewage pipe and the existing rainwater pipe and the arch of the tunnel in the vertical direction is 0.3m and 1m respectively, the diameter of the existing sewage pipe is greater than or equal to 600mm, and the diameter of the existing rainwater pipe is greater than or equal to 2000mm;

[0069] Step S300: Use small guide pipes 300 to provide advance support for the existing sewage pipes and the existing rainwater pipes, so as to form a support structure between the existing sewage pipes and the existing rainwater pipes and the arch of the tunnel.

[0070] Step S400: Continue excavating the geological body to be excavated along the exit section of the tunnel, forming the tunnel below the existing road.

[0071] In addition, if the grouting effect is poor, that is, if the strength of the grouting solidified body in the geological body 100 to be excavated does not meet the design requirements, and there is water leakage at the working face or collapse at the arch and working face, the geological body 100 to be excavated should be re-grouted at that location according to the grouting procedure, that is, grout should be added again to ensure that there is no water leakage or collapse at the working face.

[0072] For ease of understanding, a specific implementation method is shown below:

[0073] The construction methods for tunnels constructed by cutting and excavating include:

[0074] Step L100: Using the step method, excavate the geological body 100 to be excavated corresponding to the first guide face 210 at the first preset depth to form the first guide tunnel 110;

[0075] Step L200: Excavate the geological body 100 to be excavated corresponding to the second guide face 220 with a preset slope and a second preset depth, and construct the second guide tunnel 120.

[0076] Step L300: Using the step method, excavate the geological body 100 corresponding to the third guide face 230 at the third preset depth to form the third guide tunnel 130;

[0077] Step L400: Excavate the geological body 100 corresponding to the fourth guide face 240 with a preset slope and a fourth preset depth to form the fourth guide tunnel 140.

[0078] Step L500: The above steps are repeated, that is, steps S100 to S400 are repeated until the geological body 100 to be excavated is completely removed.

[0079] Step L600: Connect the first pilot tunnel 110, the second pilot tunnel 120, the third pilot tunnel 130 and the fourth pilot tunnel 140 to form a tunnel underpass.

[0080] The first preset depth is A, the second preset depth is B, the third preset depth is C, the fourth preset depth is D, B+P≤A, C+P≤B, D+P≤C, and P≥10m.

[0081] At the exit section of the tunnel, full-section grouting reinforcement is adopted, with each grouting cycle not exceeding 10m in length, and a 1-2m grout stop wall is left after each excavation. Before excavation, the soil is pre-reinforced with full-section grouting. During construction, the drilling depth, angle, and grouting pressure are controlled to ensure the grouting effect on the tunnel arch soil. Horizontal grouting is used to reinforce the top and sides of the tunnel within 1.5m, while vertical drilling grouting is used to reinforce the bottom 4.6m of the tunnel in the second guide tunnel 120 and the fourth guide tunnel 140. In fill and gravel strata, the grouting pressure is controlled at 0.5-1 MPa, and in other strata, the grouting pressure is controlled at 1-2 MPa. Based on the initially determined pressure, a grouting test is conducted in advance before formal grouting to determine reasonable grouting parameters to ensure construction safety.

[0082] It is understandable that during the cyclical execution of steps S100 to S400, since the first preset depth, the second preset depth, the third preset depth, and the fourth preset depth differ by at least 10m, after a certain period of time during the cyclical execution of steps S100 to S400, the geological body 100 to be excavated in the first guide tunnel 110 is completely removed, while the geological body 100 to be excavated still exists in the second guide tunnel 120, the third guide tunnel 130, and the fourth guide tunnel 140. In order to save construction time and improve construction efficiency, after the geological body 100 to be excavated in any of the first guide tunnel 110, the second guide tunnel 120, the third guide tunnel 130, and the fourth guide tunnel 140 is completely removed, the second tunnel construction can begin in any of the guide tunnels where the geological body 100 to be excavated has been completely removed.

[0083] Specifically, miscellaneous fill can be classified into the following types based on its material composition and the time of its filling:

[0084] (I) Classified by main material composition: 1. Plain fill: mainly composed of various soil particles, with a small amount of brick and tile fragments, slag, garbage and other debris. The organic matter content is generally less than 10%, and the soil color is still close to that of old soil. According to the type of soil, it can be further divided into: gravelly plain fill, sandy plain fill, and clayey plain fill.

[0085] 2. Construction waste soil: mainly composed of construction waste such as bricks and rubble mixed with soil.

[0086] 3. Industrial waste soil: mainly composed of slag, furnace slag, carbide slag and other industrial waste soil mixed with a small amount of soil.

[0087] 4. Household waste soil: mainly composed of household waste such as furnace ash, vegetable peels, and ceramic shards. This type of soil generally contains a high amount of organic matter and undecomposed humus.

[0088] (ii) According to the filling time: 1. Old fill: The main components are coarse particles and the filling time is more than 10 years; or the main components are fine particles and the filling time is more than 20 years.

[0089] 2. New fill: Fill that has been used for less than the period specified above is called new fill.

[0090] It is understandable that the properties and thickness of miscellaneous fill are uneven: due to the complex and different conditions of the accumulation of miscellaneous fill, the accumulation time, and especially the complexity and differences in the material source and composition, the properties of miscellaneous fill are very uneven, and the distribution range and thickness vary without regularity, with a great deal of human arbitrariness. Often, there are large variations within a very small area.

[0091] Miscellaneous fill exhibits significant deformation and collapsibility: In terms of its deformation characteristics, miscellaneous fill is often an under-compacted soil, generally possessing high compressibility. For some new miscellaneous fill, in addition to settlement under normal loads, there is also settlement under its own weight and collapsibility deformation; for domestic waste soil, there is also deformation caused by further decomposition of humus. In arid and semi-arid regions, dry or slightly moist miscellaneous fill often exhibits water immersion and collapsibility. Short accumulation time and loose structure are the main reasons for the water immersion and collapsibility and significant deformation of miscellaneous fill.

[0092] Miscellaneous fill soil has high compressibility and low strength: The material composition of miscellaneous fill soil is exceptionally complex, and different material components directly affect the engineering properties of the soil. When the composition of construction waste soil is mainly bricks, it is superior to soil mainly composed of tiles. Construction waste soil and industrial waste soil are generally superior to domestic waste soil. This is because domestic waste soil has a disordered material composition, containing a large amount of organic matter and undecomposed plant matter, resulting in high compressibility and very low strength. Even after a long period of accumulation, it remains relatively loose.

[0093] Understandably, the bench method refers to the construction method of excavating the upper section of the tunnel (upper bench) first, and then excavating the lower section (lower bench) after the upper bench has advanced a certain distance. The upper and lower benches are excavated simultaneously. According to the bench length, it can be divided into short bench, long bench, and ultra-short bench (micro bench) methods, etc.

[0094] For ease of understanding, a specific implementation method is shown below:

[0095] First, the first guide tunnel 110 is excavated on the first guide face 210. After the first guide tunnel 110 is excavated, the first initial support structure 112, the first middle partition wall 114, the first temporary invert arch 113 and the grid arch frame are erected and shotcreted.

[0096] The second guide tunnel 120 is formed by excavating the second guide face 220, and the excavation depth of the second guide tunnel 120, i.e. the second preset depth, is at least 10m different from the excavation depth of the first guide tunnel 110, i.e. the first preset depth. After the excavation of the second guide tunnel 120 is completed, the second initial support structure 121, the second middle partition wall 122, and the grid arch frame are erected and shotcreted.

[0097] The third guide tunnel 130 is formed by excavating the third guide face 230, and the excavation depth of the third guide tunnel 130, i.e. the third preset depth, and the excavation depth of the second guide tunnel 120, i.e. the second preset depth, are staggered by at least 10m. After the excavation of the third guide tunnel 130 is completed, the third initial support structure 132 and the second temporary invert arch 133 and the grid arch frame are erected and shotcreted.

[0098] The fourth guide tunnel 140 is formed by excavating the fourth guide face 240, and the excavation depth of the fourth guide tunnel 140, i.e. the fourth preset depth, is staggered from the excavation depth of the third guide tunnel 130, i.e. the third preset depth, by at least 10m. After the excavation of the third guide tunnel 130 is completed, the third initial support structure 132 and the grid arch frame are erected and shotcrete is applied.

[0099] Understandably, during excavation, full-section grouting reinforcement was strictly carried out according to the design drawings. The grouting cycle length for each reinforcement was no more than 10m, and the arc section was no more than 5m. The drilling depth, angle, and grouting pressure were carefully controlled to ensure the grouting effect on the soil in the arch of the tunnel. When the miscellaneous fill excavation of the first pilot tunnel 110 and the third pilot tunnel 130 was carried out using the step method, the step length was controlled between 2.5 and 3 meters, and the step height should match the joint position of the grating steel frame. The circumferential arch was excavated first, leaving the core soil. After the arch support structure was completed, the core soil was excavated. The excavation cycle advance of the upper and lower steps was 0.5m.

[0100] The second pilot tunnel 120 and the fourth pilot tunnel 140 were excavated using slope excavation. After the excavation of each pilot tunnel was completed, initial support work was carried out immediately to close the tunnel into a ring. During the excavation, the excavation should not exceed the cycle depth. The ground and tunnel were monitored daily to guide the construction with data and ensure construction safety.

[0101] In a preferred embodiment, the first preset depth is A, the second preset depth is B, the third preset depth is C, the fourth preset depth is D, B+P≤A, C+P≤B, D+P≤C, and P=10m.

[0102] By employing the bench excavation method and slope excavation, and sequentially constructing the first guide face 210, the second guide face 220, the third guide face 230, and the fourth guide face 240 of the excavation face 200, with excavation progresses differing by at least 10m, the first guide face 110, the second guide face 120, the third guide face 130, and the fourth guide face 140 are constructed. After the construction of the first guide face 110, the second guide face 120, the third guide face 130, and the fourth guide face 140 is completed, the first guide face 110 is demolished. The first temporary invert arch 113, the second temporary invert arch 133, the first intermediate partition wall 114, and the second intermediate partition wall 122 between the second pilot tunnel 120, the third pilot tunnel 130, and the fourth pilot tunnel 140 form a tunnel-to-underpass. This provides a safe and efficient construction method for tunnels located in miscellaneous fill layers, with excavation progresses at least 10 meters apart. Excavation of the 200-meter-long excavation face is carried out from top to bottom and from left to right, with a safety distance of at least 10 meters between excavation progresses for vertical or horizontal operations. This approach avoids simultaneous vertical and horizontal operations and allows for at least 3 days of construction time for the staggered construction steps. This period serves as the strength equalization time for the initial support structure, which includes a grid and shotcrete. The shotcrete reaches over 80% of its design strength in about 3 days, providing construction conditions for the next layer and ensuring the stability of the soil at all points of the 100-meter-long excavated geological body within the fill layer. Furthermore, during the excavation process, temporary support structures are installed in each pilot tunnel, dividing the tunnel into multiple independent working faces. Even if a collapse occurs in one pilot tunnel, timely remedial measures can be taken to prevent the entire tunnel from collapsing due to the collapse of a pilot tunnel, thus ensuring the construction safety of the tunnel within the fill layer.

[0103] It should be noted that the preset slope involved in this embodiment and other embodiments is 1:10.

[0104] Continue to refer to Figure 1 , Figure 5 and Figure 7 .

[0105] In one embodiment of the present invention, such as Figure 1 , Figure 5 and Figure 7 As shown, the steps for constructing the first guide tunnel 110 by excavating the geological body 100 corresponding to the first guide face 210 at a first preset depth using the step method include:

[0106] Step L110: Along the arch surface of the geological body 100 to be excavated, excavate the geological body 100 to be excavated corresponding to the first guide surface 210 in a circumferential manner to a first preset depth, forming a first reserved core soil 111; wherein, a first support space is formed between the top surface of the first reserved core soil 111 and the inner wall of the geological body 100 to be excavated.

[0107] Step L120: Support the arch of the geological body 100 to be excavated in the first space to be supported to form the first initial support structure 112.

[0108] Step L130: Excavate the first reserved core soil 111 and construct the first guide tunnel 110.

[0109] Specifically, after full-section grouting to reinforce the stratum, pre-grouting is performed to reinforce the stratum. The upper left first guide face 210 is excavated using the step method to form the first guide tunnel 110, and initial support is applied. Node plates are reserved on the initial support grid in the first guide tunnel 110 to facilitate subsequent steel frame connection, and corner anchors are used to reinforce the wall corners.

[0110] In one embodiment, the step of excavating the first reserved core soil 111 and constructing the first guide tunnel 110 includes:

[0111] Step L131: Excavate the first reserved core soil 111 to form the first temporary support area; wherein, the cross-section of the first temporary support area is L-shaped;

[0112] Step L132: Provide temporary support for the first area to be temporarily supported, forming the first temporary support structure;

[0113] Step L133: Connect the first temporary support structure and the first initial support structure 112 to form a first closed-loop structure, forming a first guide hole 110; wherein the cross-section of the first closed-loop structure coincides with the outer contour of the first guide surface 210.

[0114] In one embodiment, the step of temporarily supporting the first area to be temporarily supported to form a first temporary support structure includes:

[0115] Step L101: Construct the first temporary invert arch 113 on the bottom surface of the first temporary support area;

[0116] Step L102: Construct the sidewall of the first temporary support area to form a first diaphragm wall 114; wherein the first diaphragm wall 114 is located between the first guide surface 210 and the third guide surface 230;

[0117] Step L103: Connect the first temporary invert arch 113 and the first intermediate partition wall 114 to form the first temporary support structure.

[0118] Continue to refer to Figure 7 and Figure 8.

[0119] In one embodiment of the present invention, such as Figure 7 and Figure 8 As shown, the geological body 100 to be excavated corresponding to the second guide surface 220 includes the second reserved core soil 123;

[0120] The steps of excavating the geological body 100 corresponding to the second guide face 220 at a preset slope and a second preset depth to form the second guide tunnel 120 include:

[0121] Step L210: Excavate the second reserved core soil 123 below the first temporary invert arch 113 with a preset slope and a second preset depth;

[0122] Step L220: Excavate the miscellaneous fill layer below the second reserved core soil 123 at a preset slope and a second preset depth to form the second space to be supported;

[0123] Step L230: In the second space to be supported, a second initial support structure 121 is constructed; wherein, the top surface of the second initial support structure 121 is a first temporary invert arch 113.

[0124] Step L240: Construct a second temporary support structure in the second space to be supported;

[0125] Step L250: Connect the second temporary support structure and the second initial support structure 121 to form a second closed-loop structure, thereby forming a second guide hole 120; wherein the cross-section of the second closed-loop structure coincides with the outer contour of the second guide surface 220.

[0126] Specifically, the lower left second guide face 220 is excavated using the bench method to form the second guide tunnel 120, and initial support is applied. Node plates are pre-installed on the initial support grid in the second guide tunnel 120 to facilitate subsequent steel frame connection. Anchor bolts are used to reinforce the corners, and the distance between the first guide tunnel 110 and the second guide tunnel 120 along the excavation direction is at least 10m.

[0127] In one embodiment, the step of constructing a second temporary support structure in the second space to be supported includes:

[0128] Step L241: Construct a second partition wall 122 on the side wall of the second space to be supported to form a second temporary support structure; wherein, the second partition wall 122 is located between the second guide surface 220 and the fourth guide surface 240;

[0129] The steps of connecting the second temporary support structure and the second initial support structure 121 to form a second closed-loop structure to create the second guide tunnel 120 include:

[0130] Step L251: Connect the second intermediate partition wall 122 with the second initial support structure 121 to form a second closed loop structure, thereby forming the second guide tunnel 120.

[0131] Continue to refer to Figure 7 , Figure 8 and Figure 9 .

[0132] In one embodiment of the present invention, such as Figure 7 , Figure 8 and Figure 9 As shown, the steps for constructing the third guide tunnel 130 by excavating the geological body 100 corresponding to the third guide face 230 at a third preset depth using the step method include:

[0133] Step L310: Along the arch surface of the geological body 100 to be excavated, excavate the geological body 100 to be excavated corresponding to the third guide surface 230 in a circumferential manner to a third preset depth, forming a third reserved core soil 131; wherein, a third support space is formed between the top surface of the third reserved core soil 131 and the inner wall of the geological body 100 to be excavated.

[0134] Step L320: Support the arch of the geological body 100 to be excavated in the third space to be supported, forming the third initial support structure 132.

[0135] Step L330: Excavate the third reserved core soil 131 and construct the third guide tunnel 130.

[0136] Specifically, the upper right third guide face 230 is excavated using the bench method to form the third guide tunnel 130, and initial support is installed in the third guide tunnel 130. Node plates are reserved on the initial support grid in the third guide tunnel 130 to facilitate subsequent steel frame connection. Anchor bolts are used to reinforce the corners, and the distance between the third guide tunnel 130 and the second guide tunnel 120 along the excavation direction is at least 10m.

[0137] In one embodiment, the step of excavating the third reserved core soil 131 and constructing the third guide tunnel 130 includes:

[0138] Step L331: Excavate the third reserved core soil 131 to form the third temporary support zone; wherein, the cross-section of the third temporary support zone is L-shaped;

[0139] Step L332: Construct the second temporary invert arch 133 on the bottom surface of the third temporary support area;

[0140] Step L333: Connect the second temporary invert arch 133 and the first intermediate diaphragm wall 114 to form the third temporary support structure;

[0141] Step L334: Connect the third temporary support structure and the third initial support structure 132 to form a third closed loop structure, forming a third guide hole 130; wherein the cross-section of the third closed loop structure coincides with the outer contour of the first guide surface 210.

[0142] Continue to refer to Figures 5 to 10 .

[0143] In one embodiment of the present invention, such as Figures 5 to 10 As shown, the geological body 100 to be excavated corresponding to the fourth guide surface 240 includes the fourth reserved core soil 141;

[0144] The steps for excavating the geological body 100 corresponding to the fourth guide face 240 at a preset slope and a fourth preset depth, and constructing the fourth guide tunnel 140, include:

[0145] Step L410: Excavate the fourth reserved core soil 141 below the second temporary invert arch 133 with a preset slope and a fourth preset depth;

[0146] Step L420: Excavate the miscellaneous fill layer below the fourth reserved core soil 141 with a preset slope and a fourth preset depth to form the fourth space to be supported;

[0147] Step L430: In the fourth space to be supported, a fourth initial support structure 142 is constructed; wherein, the top surface of the fourth initial support structure 142 is a second temporary invert arch 133.

[0148] Step L440: Connect the fourth initial support structure 142 with the second intermediate partition wall 122 to form a fourth closed-loop structure, forming a fourth guide hole 140; wherein, the cross-section of the fourth closed-loop structure coincides with the outer contour of the fourth guide surface 240.

[0149] Specifically, the lower right fourth guide face 240 is excavated using the bench method to form the fourth guide tunnel 140, and initial support is installed in the fourth guide tunnel 140. Node plates are pre-installed on the initial support grid in the fourth guide tunnel 140 to facilitate subsequent steel frame connections. Anchor bolts are used to reinforce the corners, and the fourth guide tunnel 140 and the third guide tunnel 130 are separated by at least 10 meters along the excavation direction.

[0150] Continue to refer to Figure 10 .

[0151] In one embodiment, such as Figure 10 As shown, the steps for connecting the first pilot tunnel 110, the second pilot tunnel 120, the third pilot tunnel 130, and the fourth pilot tunnel 140 to form a tunnel underpass include:

[0152] Step L610: Remove the first temporary invert arch 113, the second temporary invert arch 133, the first intermediate partition wall 114 and the second intermediate partition wall 122 to connect the first pilot tunnel 110, the second pilot tunnel 120, the third pilot tunnel 130 and the fourth pilot tunnel 140 to form a tunnel underpass.

[0153] Specifically, the first intermediate partition wall 114 and the second intermediate partition wall 122 are dismantled in sections from bottom to top (section length ≤ 6m), a waterproof layer is applied, and the secondary lining is poured.

[0154] After the first temporary invert arch 113, the second temporary invert arch 133, the first intermediate partition wall 114, and the second intermediate partition wall 122 are completely demolished, a waterproof layer is applied to the inner walls of the first pilot tunnel 110, the second pilot tunnel 120, the third pilot tunnel 130, and the fourth pilot tunnel 140, and the remaining secondary lining is poured to form a tunnel under tunnel.

[0155] In a specific project, as one possible implementation method of this solution:

[0156] (I) Full-section grouting reinforcement: According to the design drawings, the A entrance / exit section will be reinforced with full-section grouting. The grouting cycle length for each reinforcement will not exceed 10m, and a 1-2m grout stop wall will be left after each excavation. Before excavation, the soil will be reinforced with full-section grouting. During construction, the drilling depth, angle, and grouting pressure will be controlled to ensure the grouting effect on the soil at the tunnel arch. Horizontal grouting will be used to reinforce the top and sides of the tunnel within a 1.5m range, while vertical drilling grouting will be used to reinforce the bottom 4.6m range of the tunnel in the second guide tunnel 120 and the fourth guide tunnel 140.

[0157] In fill and gravel strata, the grouting pressure should be controlled at 0.5–1 MPa, while in other strata, the grouting pressure should be controlled at 1–2 MPa. Based on the initially determined pressure, a grouting test should be conducted before formal grouting to determine reasonable grouting parameters to ensure construction safety.

[0158] (II) Earthwork excavation: 1. Excavation shall be carried out, and the distance between the excavation of each pilot tunnel shall not be less than 10m.

[0159] 2. When using the bench method for earthwork excavation, the bench length should be controlled between 2.5 and 3 meters, and the bench height should match the joint position of the grating steel frame. First, excavate the circumferential arch section, leaving core soil. After the arch support structure is completed, excavate the core soil, extending 5cm beyond the design dimensions at the edge. The edge excavation should be promptly trimmed to ensure a smooth excavation outline and a flat excavation surface. The excavation cycle for both upper and lower benches is 0.5 meters. After excavation, initial support work should be carried out immediately to close the ring. During excavation, exceeding the cycle advance is prohibited to ensure construction safety.

[0160] 3. During the excavation of the upper bench, a core soil layer is reserved. The core soil layer has a trapezoidal cross-section. For the first guide tunnel (110) and the third guide tunnel (130), the core soil layer is 1m high and 0.5m and 1.5m wide at the top and bottom, respectively. For the second guide tunnel (120) and the fourth guide tunnel (140), slope excavation is adopted. During the excavation of the upper bench, the arch is excavated first, followed by the arch waist. The grid frame is erected first at the arch waist, then at the arch. After the arch excavation is completed, a 4cm layer of initial shotcrete is applied to the excavation surface, and then the grid steel frame is erected. For the lower bench construction, the core soil is excavated first, followed by the partial excavation of the lower soil. The grid steel frame is erected, and the initial lining is constructed. Slope excavation should be carried out during the lower bench construction to ensure soil stability. It is ensured that during the excavation of each section, the area between the arch excavation surface and the core soil layer is limited to the grid area, minimizing the exposed area of ​​the working face. This allows for immediate handling should a collapse occur.

[0161] (III) Steel grating installation: After the earthwork excavation is completed, the steel grating should be installed immediately to ensure the stability of the working face.

[0162] 1. The base surface should be firm and clean, and pre-reinforcement should be carried out if necessary.

[0163] 2. The steel grating frame is erected after the initial spraying is 30mm thick (the initial spraying is carried out in sections prone to collapse, depending on the geological conditions) and the mesh is hung.

[0164] 3. To fully utilize the rigidity of the arch frame and optimize the stress state of both the arch frame and the surrounding rock, the arch frame should be installed tightly against the initial shotcrete. Each steel grating node and adjacent steel gratings must be securely connected longitudinally. During installation, concrete pads should be placed where there is a large gap between the steel frame and the initial shotcrete layer. The contact distance between the steel frame and the surrounding rock (or pads) should not exceed 50mm. To enhance the overall stability of the steel frame, it should be welded to the 300mm guide pipe.

[0165] 4. The spacing between the grid arches is 50cm, and they should be perpendicular to the centerline of the line. The allowable deviations are: lateral ±20mm, longitudinal ±30mm, elevation ±15mm, and verticality 5‰; the thickness of the steel frame protective layer is 30mm, with an allowable deviation of -5mm.

[0166] 5. The longitudinal connecting bars of the grating steel frame are φ22, single-sided welding is adopted, the lap length is ≥10d, the circumferential spacing is 1m, and the connecting bars are staggered inside and outside the main bars.

[0167] 6. When bolt connections at the grid joints are difficult and the connecting plates are not tightly fitted, four steel bars of the same diameter as the main reinforcement should be welded together to achieve equal strength connections. Single-sided welding should be used, and the lap length should be ≥10d.

[0168] 7. After the grid is erected, the loose soil at the base of the grid should be removed in time, and a 100mm thick shotcrete pad should be made or square timber should be used as the foundation for the base of the grid to ensure the stability of the grid base.

[0169] 8. According to the construction sequence, corner anchor pipes should be installed at each step, one pipe at each step, to prevent the grid from sinking. The corner anchor pipes are DN32 welded steel pipes with a length of 2.5m. Depending on the geological conditions, single-component cement grout should be used in the gravel layer, modified water glass should be used in the fine sand and fine medium sand layers, and cement-water glass double-component grout should be used in the other layers.

[0170] 9. After erecting the steel frame, carry out shotcrete work as soon as possible, and completely cover the steel frame so that the steel frame and shotcrete share the load. When shotcreting, spray from the arch foot or wall foot upwards to prevent the upper layer of shotcrete from being insufficiently compacted and causing insufficient strength and instability of the arch foot.

[0171] (IV) Reinforcing Mesh Processing and Installation: The reinforcing mesh is made of φ6 steel bars, processed into 2*0.7m (mesh size 150×150mm) meshes. The intersections of the reinforcing bars are spot-welded. During construction, the mesh is transported to the work surface for welding and installation. The outer reinforcing mesh is installed simultaneously with the steel frame after the initial shotcrete. Before installation, depending on the geological conditions, a 3cm thick layer of concrete is first shotcreted in sections prone to collapse. The reinforcing mesh is then laid on the concrete surface and welded to the steel frame or anchor pipes. The inner reinforcing mesh is installed after the grid steel frame is completed. The reinforcing meshes must be securely overlapped, with an overlap length of not less than 150mm, and tied to the steel frame or anchor bolts.

[0172] (V) Construction of anchor pipe for locking foot: The anchor pipe is made of DN32 (t=2.75mm) steel welded pipe with a length of 2.5m. One anchor pipe is installed for each guide hole. The anchor pipe is installed at the connection of the steel plate of the grid steel frame at both ends. The anchor pipe is installed at a downward angle of 30° and is firmly welded to the grid.

[0173] (vi) Shotcrete Construction Process: Shotcrete operation involves mixing dry mix material and an appropriate amount of water according to the design ratio, pressing it to the nozzle using a shotcrete machine, adding a quick-setting agent and some water to the nozzle, and then spraying it out. According to the design requirements, the shotcrete thickness of the initial support sidewall of the tunnel is 350mm, using C25 concrete.

[0174] (vii) Grouting behind the initial support: Grouting behind the initial support should be carried out in a timely manner during construction. After the initial support is closed, cement grout should be injected. The grouting pressure should be controlled at 0.3-0.5 MPa. Based on the results of ground deformation monitoring, multiple groutings should be carried out as necessary to control ground settlement.

[0175] Before shotcreting the initial support structure, grouting pipes are pre-embedded, and back grouting is carried out promptly after the initial support of the pilot tunnel is completed. The grouting pipes are DN32×2.75 welded steel pipes with a length of 0.5m. The length can be appropriately increased if there is over-excavation. The water-facing side of the grouting pipe should be in close contact with the soil, and the exposed length after shotcreting should be 100mm.

[0176] The grouting pipes are pre-embedded during the installation of the reinforcing grid, and the burial range is the tunnel arch and sidewalls. The circumferential spacing is 2m for the arch and 3m for the sidewalls; the longitudinal spacing is 3m, arranged in a quincunx pattern, and firmly welded to the grid.

[0177] The grouting material is cement grout, which is injected after the initial support structure is sealed into a ring.

[0178] Grouting is carried out in multiple stages: the first stage is low-pressure grouting, 3-5m from the excavation face, with the grouting pressure controlled to prevent grout from overflowing from the excavation face; the second stage is full-pressure grouting, 8-10m from the excavation face, with a grouting pressure of 0.5MPa.

[0179] During the construction of the tunnel, the above-mentioned construction plan was adopted, and the ground and the tunnel were monitored. If any warning was detected during the monitoring, measures such as adjusting the excavation step distance and grouting reinforcement were immediately taken to eliminate the warning, ensuring the safety of the tunnel construction. No safety accidents occurred, and the project benefits were improved.

[0180] It should be noted that, in this embodiment and other embodiments, since the strata of the geological body to be excavated are mainly filled soil layers, in order to control the diffusion radius, the grouting material is a cement-water glass two-component grout with a grout mix ratio of 1:1. The cement is P.O42.5 ordinary Portland cement; the modulus of the water glass is 2.2 to 2.8, and the mass ratio of cement to water is 1:1; the water glass content is 30 to 40 Be'.

[0181] This invention employs the CRD method for tunnel excavation, strictly adhering to the eighteen-character principle of "advanced pipe laying, rigorous grouting, short excavation, strong support, frequent measurement, and early closure" for tunnel construction. During excavation, full-section grouting reinforcement is strictly carried out according to the design drawings. Each grouting cycle length does not exceed 10m, and the arc segment does not exceed 5m. Drilling depth, angle, and grouting pressure are carefully controlled to ensure the grouting effect on the arch soil inside the tunnel. When using the step method for excavation of pilot tunnels No. 1 and No. 3, the step length is controlled between 2.5 and 3 meters, and the step height should match the joint position of the grating steel frame. The circumferential arch is excavated first, leaving the core soil. After the arch support structure is completed, the core soil is excavated. The excavation cycle for the upper and lower steps is 0.5m. The second and fourth pilot tunnels were excavated using a slope-cutting method. After each pilot tunnel was excavated, initial support work was immediately carried out to close it into a ring. During excavation, the excavation process was not allowed to exceed the allowed cycle depth. When passing under DN600 sewage pipelines and DN2000 rainwater pipelines, pre-installed small guide pipes were installed. Daily monitoring of the pipelines and tunnels was conducted to guide construction with data and ensure construction safety. The strata were stabilized by full-section grouting to prevent water seepage at the tunnel face or the collapse of the tunnel face due to loose fill at the arch, which could cause pipeline detachment. Pre-installed small guide pipes were also installed under the pipelines to support the sewage and rainwater pipelines, preventing pipeline detachment and disruption to residents' normal lives, thus preventing adverse social impacts and loss of benefits.

[0182] In one embodiment, the step of grouting and reinforcing the geological body to be excavated to form a reinforced zone includes:

[0183] Step S110: Based on the preset drilling depth, preset drilling angle and preset grouting pressure, the geological body to be excavated is reinforced by cyclic grouting using a full-section grouting method to form the reinforced zone;

[0184] The reinforced area is located on the arch of the tunnel.

[0185] In one embodiment, the preset drilling depth is 10m, the preset drilling angle is α, 0°≤α≤45°, and the preset grouting pressure is P, 0.3Mpa≤P≤0.5Mpa.

[0186] Continue to refer to Figure 1 and refer to Figure 2 , Figure 2 for Figure 1 A detailed flowchart of the process before step S200.

[0187] In one embodiment, such as Figure 1 and Figure 2As shown, prior to the step of vertically tunneling under the existing road in the vertical direction to form the exit section of the tunnel in the geological body to be excavated, the construction method of the tunnel vertically tunneling under the existing pipeline further includes the following steps:

[0188] Step A100: Obtain the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone;

[0189] Step A200: Determine whether the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone meets the preset conditions;

[0190] Step A300: If not, perform secondary grouting reinforcement on the geological body to be excavated corresponding to the reinforcement zone until the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone meets the preset conditions.

[0191] In one embodiment, the step of performing secondary grouting reinforcement on the geological body to be excavated corresponding to the reinforcement zone until the reinforcement strength of the geological body to be excavated corresponding to the reinforcement zone meets the preset condition includes the following steps:

[0192] Step A310: Set the grouting pressure to F1, and use the grouting pressure of F1 to perform secondary grouting reinforcement on the geological body to be excavated corresponding to the reinforcement zone;

[0193] Step A320: During the secondary grouting reinforcement of the geological body to be excavated corresponding to the reinforcement zone, the value of the grouting pressure F1 is gradually changed to F2; wherein, 0 MPa ≤ F1 < 0.5 MPa, F1 < F2 ≤ 0.5 MPa.

[0194] In one embodiment, prior to the step of using small conduits 300 to provide advance support for the existing sewage pipe and the existing rainwater pipe to form a support structure between the existing sewage pipe and the existing rainwater pipe and the arch of the tunnel, the construction method for the tunnel to vertically pass under the existing pipelines further includes the following steps:

[0195] Step B100: Install advance small guide pipes between the existing sewage pipe and the existing rainwater pipe and the arch of the underground tunnel using welded steel pipes.

[0196] In one embodiment, the step of continuing to excavate the geological body to be excavated along the exit section of the tunnel to form the tunnel beneath the existing road includes:

[0197] Step S410: Continue excavating the geological body to be excavated along the exit section of the tunnel to form a tunnel to be supported;

[0198] Step S420: Initial support is provided for the passage to be supported to form an initial support structure; wherein the initial support structure is housed in the passage to be supported, and one side of the initial support structure is against the geological body to be excavated in the passage to be supported.

[0199] Step S430: Set the grouting pressure to F3, and use the grouting pressure of F3 to backfill the geological body to be excavated covered by the initial support structure to form the tunnel under the existing road; wherein, 0.3Mpa≤F3≤0.5Mpa.

[0200] In one specific embodiment, a φ600 sewage pipeline and a φ2000 rainwater pipeline are passed under the tunnel. The entire cross-section is reinforced with deep hole grouting. The reinforcement range is 1.5-5.4m outside the initial support, and the grouting pressure is controlled at 0.3Mpa-0.5MPa.

[0201] 2. Before each cycle of deep hole grouting, a grout-stopping wall with a thickness of 300mm is set on the face of the working face outside the core soil of the upper bench (2.0m inward from the inner outline of the excavation). The wall is made of C20 shotcrete and has a double layer of φ6@150×150 steel mesh.

[0202] 3. Pipeline data shall be provided by the surveying unit. Before construction, the elevation of the pipelines shall be measured to clarify their relationship with the structure. The pipe diameter, material, interface location, burial depth, leakage situation, property owner, and current usage status shall be investigated. Monitoring and measurement of the pipelines shall be strengthened to ensure pipeline safety. At the same time, hazardous gas detection shall be carried out to ensure personal safety.

[0203] 4. During construction, close attention should be paid to changes in the soil, measurements should be strengthened, measurement information should be fed back in a timely manner, and support parameters should be adjusted in a timely manner according to the measurement results to ensure the quality of the project.

[0204] 5. After grouting is completed, the grouting effect must be tested, using the in-situ testing method specified in the "Code for Geotechnical Engineering Investigation". Any weak areas should be re-grouted.

[0205] 6. Since the φ600 sewage pipe is 0.3m away from the arch crown and the φ2000 rainwater pipe is 1m away from the arch crown, while the deep hole grouting reinforcement is carried out, a φ32×2.75mm steel welded pipe is installed at the arch crown to carry out secondary grouting reinforcement of the arch.

[0206] 7. If a small-scale local collapse occurs during the excavation process, excavation should be stopped immediately and the excavation face should be sealed. Construction can only continue after reliable measures to prevent further collapse have been developed, based on the geological conditions, the scope and location of the collapse.

[0207] 8. Pipeline protection measures should be agreed upon with the pipeline owner. The reinforcement measures for sewage pipelines are reinforced spiral wound pipes using an anti-seepage process, and the reinforcement measures for rainwater pipelines are 5mm thick ultraviolet-cured anti-seepage technology. The underground excavation at the inlet / outlet will pass under a 2000mm rainwater pipeline (D=2000mm) for 28.5m and a 60.0m sewage pipeline (D=600mm); the underground excavation at inlet / outlet D will pass under a 2000mm rainwater pipeline (D=2000mm) for 29.5m and a 70.0m sewage pipeline (D=600mm). The total length of the rainwater pipeline is 58m, and the total length of the sewage pipeline is 130m.

[0208] 9. After the initial support construction is completed, backfilling and grouting should be carried out multiple times behind it in a timely manner to reduce ground settlement. The grouting pressure should be controlled at 0.3-0.5 MPa, and excessive pressure should be strictly prevented from causing ground heave.

[0209] 10. During construction, close attention should be paid to changes in the soil, and measurement information should be reported in a timely manner. If the settlement is too large, measures such as directional grouting should be taken to ensure construction safety.

[0210] 11. Construction monitoring and measurement should be carried out throughout the entire construction process, and inspection work should be strengthened during the construction process.

[0211] 12. When the pipeline deformation is too large, the following measures should be taken proactively to ensure pipeline safety.

[0212] 1) Grouting should be carried out in areas of excessive pipeline deformation. At the same time, pipeline monitoring should be strengthened, and the grouting pressure, materials, locations and grouting volume should be adjusted according to the monitoring results in order to actively control pipeline settlement and bulging.

[0213] 2) Contact the pipeline owner in a timely manner to carry out emergency repairs on the parts that are excessively deformed or damaged.

[0214] Continue to refer to Figure 1 and refer to Figure 3 , Figure 3 for Figure 1 A detailed flowchart of step S300.

[0215] In one embodiment, such as Figure 1 and Figure 3 As shown, the step of using small guide pipes 300 to provide advance support for the existing sewage pipes and existing rainwater pipes to form a support structure between the existing sewage pipes and existing rainwater pipes and the arch of the tunnel includes:

[0216] Step S310: Using a water drill, drill holes along the circumferential direction in the arch of the tunnel to the geological body to be excavated corresponding to the reinforced area, forming multiple installation holes;

[0217] Step S320: Fabricate multiple small guide tubes 300; wherein the number of small guide tubes 300 is consistent with the number of mounting holes and is set in a one-to-one correspondence;

[0218] Step S330: Insert each of the small guide tubes 300 into the corresponding mounting holes;

[0219] The small conduits 300 and the grid together form the support structure.

[0220] In one embodiment, the spacing between two adjacent mounting holes in the plurality of mounting holes is 300 mm, and each mounting hole is distributed in a 140° curve in the geological body to be excavated corresponding to the reinforcement area.

[0221] Specifically, the small conduit 300 is installed after the grid is installed when the pipeline is laid down, with a circumferential spacing of 300mm, a longitudinal spacing of 1m, and an arch of 140°. The small conduit 300 is installed at an elevation angle of 10° to 20°.

[0222] Continue to refer to Figure 1 and Figure 3 and refer to Figure 4 , Figure 4 for Figure 3 A detailed flowchart of step S320.

[0223] In one embodiment, such as Figure 1 , Figure 3 and Figure 4 As shown, the construction method for vertically tunneling under existing pipelines using steel pipes includes the following steps for fabricating multiple small guide pipes 300:

[0224] Step S321: Cut the front end of the steel pipe into a pointed cone shape;

[0225] Step S322: Arrange multiple grout discharge holes in the middle of the steel pipe; wherein the multiple grout discharge holes are distributed in a quincunx pattern, and the distance between two adjacent grout discharge holes is D, 20cm≤D≤30cm;

[0226] Step S323: Use the rear end of the steel pipe as the grout-stopping section;

[0227] Step S324: Weld reinforcing steel hoops to the tail of each steel pipe to form the support structure together with the grid.

[0228] Specifically, to improve the grouting effect of the geological body 100 to be excavated, and to make the driving process of the small guide pipe 300 easier to control and improve the construction accuracy of the geological body 100 to be excavated, the small guide pipe 300 is made of DN32 (t=2.75mm) steel pipe processed on site. The front end of the pipe is cut into a pointed cone shape. In the middle of the guide pipe, 1-1.5m range, gushing grout drain holes are arranged. The diameter of the drain holes is 6-8mm and the spacing between the holes is 20-30cm. The tail 50cm range is left undrilled as a grout stop section. Reinforcing steel hoops are welded to the tail of the guide pipe. The small guide pipe 300 is 2.5m long, with a circumferential spacing of 300mm and a longitudinal spacing of 1m. It is driven within a 140° arch range, and the driving angle of the small guide pipe 300 is 10°-20°.

[0229] Understandably, to improve the installation accuracy of the small guide pipe 300 and facilitate its insertion into the geological body 100 to be excavated, the installation of the small guide pipe 300 involves drilling a hole at the location of the small guide pipe 300 using a water drill before the grid is installed and the shotcrete is applied. The small guide pipe 300 is then driven into the hole formed by the water drill, i.e., the installation position. Considering the geological characteristics of the underground excavation section, in the miscellaneous fill strata, a water drill is used to drill the hole before driving the small guide pipe 300 in; for the silty sand strata, a blow-hole is used. In the silty sand layer, the small guide pipe 300 is connected to an air compressor, and the silty sand in front of the small guide pipe 300 is blown out by the air pressure, thus sending the small guide pipe 300 to the design depth.

[0230] It should be noted that the sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. The above embodiments are only optional embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made under the inventive concept of the present invention using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are all included within the patent protection scope of the present invention.

Claims

1. A construction method for a tunneling channel vertically underpassing an existing pipeline, characterized in that, The method comprises: Grouting reinforcement is performed on the to-be-excavated geological body to form a reinforced area; this step comprises performing cyclic grouting reinforcement on the to-be-excavated geological body in a full-face grouting manner according to a preset drilling depth, a preset drilling angle and a preset grouting pressure, so as to form the reinforced area; wherein the reinforced area is arranged at the vault of the underground excavation passage; Corresponding to the reinforced area, the to-be-excavated geological body is vertically excavated along the vertical direction to form an outlet section of the underground excavation passage; wherein the existing road is buried below the existing sewage pipe and the existing rainwater pipe, and the spacing between the existing sewage pipe and the existing rainwater pipe and the vault of the underground excavation passage in the vertical direction is 0.3 m and 1 m, the diameter of the existing sewage pipe is greater than or equal to 600 mm, and the diameter of the existing rainwater pipe is greater than or equal to 2000 mm; Small pipes are used to perform advanced support on the existing sewage pipe and the existing rainwater pipe to form a support structure between the existing sewage pipe and the existing rainwater pipe and the vault of the underground excavation passage; this step comprises drilling a plurality of installation holes in the to-be-excavated geological body corresponding to the reinforced area along the circumferential direction at the vault of the underground excavation passage; a plurality of small pipes are manufactured; wherein the number of small pipes is consistent with and one-to-one corresponds to the number of installation holes; each small pipe is driven into the corresponding installation hole; wherein each small pipe and the grid jointly form the support structure; The to-be-excavated geological body is continuously excavated along the outlet section of the underground excavation passage to form the underground excavation passage below the existing road; this step comprises continuously excavating the to-be-excavated geological body along the outlet section of the underground excavation passage to form a to-be-supported passage; the to-be-supported passage is initially supported to form an initial support structure; wherein the initial support structure is accommodated in the to-be-supported passage, and one side of the initial support structure is arranged on the to-be-excavated geological body in the to-be-supported passage; the grouting pressure is set to F3, and the to-be-excavated geological body covered by the initial support structure is backfilled and grouted using the grouting pressure with a value of F3 to form the underground excavation passage below the existing road; wherein 0.3 Mpa≤F3≤0.5 Mpa; Before the step of using small pipes to perform advanced support on the existing sewage pipe and the existing rainwater pipe to form a support structure between the existing sewage pipe and the existing rainwater pipe and the vault of the underground excavation passage, the method further comprises: A steel welded pipe is used to drive an advanced small pipe between the existing sewage pipe and the existing rainwater pipe and the vault of the underground excavation passage.

2. The construction method of the tunneling channel vertically underpassing existing pipelines according to claim 1, characterized in that, The preset drilling depth is 10 m, the preset drilling angle is α, 0°≤α≤45°, and the preset grouting pressure is P, 0.3 Mpa≤P≤0.5 Mpa.

3. The construction method of the tunneling channel vertically underpassing existing pipelines according to claim 2, characterized in that, Before the step of corresponding to the reinforced area, vertically excavating the to-be-excavated geological body along the vertical direction to form an outlet section of the underground excavation passage, the method further comprises: The reinforcement strength of the to-be-excavated geological body corresponding to the reinforced area is obtained; determining whether the reinforcement strength of the to-be-excavated geological body corresponding to the reinforcement area meets a preset condition; if not, performing secondary grouting reinforcement on the to-be-excavated geological body corresponding to the reinforcement area until the reinforcement strength of the to-be-excavated geological body corresponding to the reinforcement area meets the preset condition.

4. The construction method of a tunneling channel vertically underpassing existing pipelines according to claim 3, characterized in that, The step of if not, performing secondary grouting reinforcement on the to-be-excavated geological body corresponding to the reinforcement area until the reinforcement strength of the to-be-excavated geological body corresponding to the reinforcement area meets the preset condition includes: setting the grouting pressure to F1, and using the grouting pressure with the numerical value of F1 to perform secondary grouting reinforcement on the to-be-excavated geological body corresponding to the reinforcement area; during the secondary grouting reinforcement on the to-be-excavated geological body corresponding to the reinforcement area, adjusting the numerical value F1 of the grouting pressure to gradually change to F2; wherein 0Mpa≤F1<0.5Mpa, F1<F2≤0.5Mpa.

5. The construction method of a tunneling channel vertically underpassing existing pipelines according to claim 1, characterized in that, The spacing between two adjacent installation hole positions in the plurality of installation hole positions is 300mm, and each installation hole position is distributed in a curve of 140° on the to-be-excavated geological body corresponding to the reinforcement area.

6. The construction method of a tunneling channel vertically underpassing existing pipelines according to claim 5, characterized in that, For steel pipes, the step of manufacturing a plurality of small conduits includes: cutting the front end of the pipe body of the steel pipe into a sharp cone shape; arranging a plurality of grout leakage holes in the middle part of the pipe body of the steel pipe; wherein a plurality of grout leakage holes are distributed in a quincunx shape, and the spacing between two adjacent grout leakage holes in the plurality of grout leakage holes is D, 20cm≤D≤30cm; using the rear end of the pipe body of the steel pipe as a grout stop section; welding a steel reinforcement hoop at the tail of each pipe body of the steel pipe to form the support structure together with the grid.

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