A method for parallel expansion of multiple tunnel sections using existing tunnels to accelerate construction

Abstract

The present invention discloses a method for parallel expansion of multiple sections of a tunnel by utilizing an existing tunnel to accelerate construction. The method utilizes the existing tunnel as a pilot tunnel for advance construction and divides the tunnel expansion construction section into a parallel working section of the existing tunnel and a circulating working section of the expanded tunnel. The parallel working section of the existing tunnel performs lateral refined geological prediction of the surrounding rock of the tunnel, advance drainage, advance grouting reinforcement, and drilling of blastholes on the side of the tunnel expansion according to a segmented parallel construction process; the circulating working section of the expanded tunnel performs lateral micro-difference blasting excavation of the surrounding rock, slag loading and transportation, mechanized demolition of the existing tunnel structure, and installation of the support structure of the expanded tunnel according to a segmented flow construction process; the relatively time-consuming surrounding rock geological prediction, surrounding rock reinforcement, and blasthole drilling construction are completed in advance in the parallel working section of the existing tunnel, thereby cleverly reducing the number of circulating construction processes in the circulating working section of the expanded tunnel, significantly improving the tunnel construction safety, and greatly improving the tunnel expansion construction speed. The method is suitable for the renovation and expansion construction of various types of tunnels.

Description

Technical Field

[0001] The invention relates to a method for parallel expansion of multiple sections of a tunnel by utilizing an existing tunnel to accelerate construction, and belongs to the technical field of tunnel construction. Background Art

[0002] The capacity of some early-constructed highways is severely insufficient. To meet the growing demand for transportation, the construction of new highways or the expansion and reconstruction of existing highways are effective solutions. Highway expansion and reconstruction can effectively improve the capacity and performance of existing lines and has gradually become a widely recognized solution for expanding the highway network. Due to the influence of existing line structures, highway expansion and reconstruction construction is often more complex than new highway construction, and the related construction is more challenging, requiring the high attention of engineering and technical personnel. As an important part of highway expansion and reconstruction construction, tunnel expansion construction involves the demolition of existing lining structures, surrounding rock excavation, and structural reconstruction, which causes significant disturbance and damage to the surrounding rock around the tunnel. If improperly handled during construction, it is very likely to cause large-scale tunnel collapse accidents.

[0003] At the same time, to quickly restore road traffic capacity, renovation and expansion projects typically impose extremely strict construction deadlines. This leads to a series of challenges for tunnel expansion, including tight deadlines, high construction risks, and complex procedures. The difficulty far exceeds that of conventional new tunnel construction. Currently, research on tunnel expansion construction is relatively limited and remains in the early stages of practical exploration. Considering the relevant construction conditions for tunnel expansion, it is of great practical significance to develop a method for parallel expansion of multiple sections of a tunnel that utilizes existing tunnels to accelerate construction. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for parallel expansion of multiple sections of a tunnel by utilizing existing tunnels to accelerate construction, which can overcome the shortcomings of the existing technology.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for parallel expansion of multiple sections of a tunnel by utilizing existing tunnels to accelerate construction comprises the following steps:

[0007] s1. Using the existing tunnel as a pilot tunnel for preliminary construction, the tunnel expansion construction area is divided into multiple construction sections, and within each construction section, a parallel working section for the existing tunnel and a circular working section for the expansion tunnel are divided;

[0008] s2. Carry out auxiliary construction work and preliminary preparation work before tunnel expansion in the parallel working area of ​​the existing tunnel;

[0009] s3. Carry out expansion construction simultaneously within the expansion tunnel's circular working area, including: excavation of surrounding rock for the upper and middle steps of the expansion tunnel, demolition of the existing tunnel superstructure, and construction of the initial support structure for the upper and middle steps of the expansion tunnel;

[0010] s4. In the middle section of the expanded tunnel's circular working area, the existing structure of the lower step of the expanded tunnel will be demolished and surrounding rock excavation will be carried out, and the initial support structure of the lower part of the expanded tunnel will be constructed;

[0011] s5. Construction of the expanded tunnel invert, invert backfill, secondary lining and other structures shall be carried out in the rear section of the expanded tunnel circulation working area.

[0012] The aforementioned method for parallel expansion of multiple tunnel sections uses a segmented parallel construction process to conduct lateral geological forecasting, advanced surrounding rock treatment, and blasthole drilling construction in the front, middle, and rear sections of the existing tunnel's parallel working sections; and a segmented flow construction process to conduct surrounding rock excavation, slag loading and transportation, mechanized demolition of the existing tunnel structure, and construction of the expansion tunnel's support structure in the expanded tunnel's circulating working section.

[0013] In the aforementioned method for parallel expansion of multiple sections of a tunnel, in step s1, multiple construction sections are set up according to the layout of existing vehicle and pedestrian cross passages in the tunnel, and include regular construction sections and intermittent construction sections; multiple construction sections can be organized for construction in parallel.

[0014] The aforementioned method for parallel expansion of multiple sections of tunnels only arranges one conventional construction section for short tunnels without pedestrian cross passages; for medium tunnels with pedestrian cross passages, a conventional construction section is arranged at the tunnel entrance and exit ends; for long or extra-long tunnels with pedestrian cross passages and emergency parking lanes, in addition to a conventional construction section at the tunnel entrance and exit ends, intermittent construction sections can be added based on the pedestrian cross passages and emergency parking lanes, and the number of intermittent construction sections matches the number of emergency parking lanes.

[0015] In the aforementioned multi-section parallel tunnel expansion method, in step s2, the tunnel excavation construction direction is used as the forward direction, the existing tunnel parallel working section is arranged in front of the expansion tunnel circular working section, and the existing tunnel parallel working section is divided into three working sections: front, middle, and rear. The work division is as follows:

[0016] (1) Conduct multi-section transverse detailed geological prediction of the tunnel surrounding rock in the front section of the parallel working section of the existing tunnel;

[0017] (2) Based on the geological prediction and exploration results, advance treatment of the surrounding rock is carried out in the middle section of the parallel working section of the existing tunnel, including lateral drainage and consolidation of the surrounding rock and grouting and reinforcement of the surrounding rock shell;

[0018] (3) Based on the geological prediction and detection results, the blasting parameters related to the horizontal micro-difference blasting are designed, and then the drilling construction of the relevant blastholes is carried out in the rear section of the parallel working section of the existing tunnel.

[0019] The aforementioned method for parallel expansion of multiple tunnel sections specifically includes:

[0020] 1) Based on the results of short-distance geological exploration at multiple longitudinal sections of the tunnel, a relatively accurate geological exploration model of the surrounding rock mass around the tunnel is formed;

[0021] 2) When geological detection indicates that the surrounding rock is rich in water, drainage holes can be constructed in the middle section of the parallel working section of the existing tunnel, from the interior of the existing tunnel to the deep surrounding rock to drain the groundwater in advance, thereby improving the construction environment in the tunnel excavation section. At the same time, grouting holes can be drilled in the middle section of the parallel working section of the existing tunnel, from the interior of the existing tunnel to the deep surrounding rock, to grout and reinforce the surrounding rock outside the outline of the expansion tunnel, thus forming a reliable surrounding rock grouting reinforcement shell outside the excavation outline of the expansion tunnel before the surrounding rock excavation begins.

[0022] 3) In the rear section of the parallel working area of ​​the existing tunnel, drilling construction of relevant blastholes is carried out into the surrounding rock of the expanded excavation side in a dense longitudinal arrangement.

[0023] The aforementioned method for parallel expansion of multiple tunnel sections specifically includes:

[0024] 1) The horizontal short-distance geological prediction detection range is 10 to 15 meters outside the existing tunnel outline;

[0025] 2) By using grouting pipes of different lengths and setting grouting stops of different lengths at the ends of the grouting pipes, a radial skipping grouting effect is achieved, whereby only the surrounding rock outside the outline of the expanded tunnel is reinforced by grouting without grouting within the expanded tunnel.

[0026] 3) If blastholes are drilled in advance, casing can be inserted into the blastholes to prevent them from collapsing due to the vibration of tunnel blasting. In addition, if the horizontal drainage holes and grouting holes drilled in the early stage are in the right position, they can be used directly as blastholes to reduce the workload of blasthole construction.

[0027] In the aforementioned multi-section parallel tunnel expansion method, in step s3, the tunnel excavation construction direction is used as the forward direction, and the expanded tunnel circular working section is divided into three working sections: front, middle, and back. The front section of the expanded tunnel circular working section is further subdivided into the existing tunnel side circular working section and the tunnel excavation side circular working section. The work division is as follows:

[0028] (1) Using an alternating construction method, the upper and middle steps of the tunnel expansion side circulation working area are sequentially carried out with explosive blasting, slag loading and transportation, and initial support construction;

[0029] (2) Carry out mechanized dismantling of the tunnel support structure away from the excavation side and initial support construction in the circulation working section on the existing tunnel side, and connect the initial support on the excavation side and the side away from the excavation side together;

[0030] (3) Carry out mechanized demolition of the tunnel support structure close to the expansion side in the circulation working section on the existing tunnel side.

[0031] The aforementioned method for parallel expansion of multiple tunnel sections specifically includes:

[0032] 1) First, blasting construction is carried out on the upper steps of the circular working area on the tunnel expansion side. After the slag is loaded and transported, the initial support of the relevant sections is carried out in a timely manner. Then, blasting excavation, slag loading and transportation, and initial support construction are carried out on the middle steps of the circular working area on the tunnel expansion side.

[0033] Loading the gun: charging the middle and rear sections of the blasthole, and filling the front section with gun mud to seal the blasthole;

[0034] The detonation sequence is set to micro-difference detonation: first detonate the upper blastholes of the first ring, then successively detonate the middle and lower blastholes of the first ring; after the first ring is blasted, detonate the next ring of blastholes in succession according to the above rules; the number of blastholes to be detonated at one time should be determined according to the surrounding rock conditions; if the surrounding rock is relatively stable, one or two more rings can be blasted, but a maximum of three rings of blastholes can be blasted at one time to ensure sufficient free surface for each blast; at the same time, the energy of lateral blasting is mainly released in the direction with free surface, which can throw the surrounding rock backward along the tunnel expansion direction;

[0035] 2) The existing tunnel lining structure away from the excavation side is removed in sections, and then the tunnel excavation section is trimmed. The initial support structure away from the excavation side is constructed in a timely manner, and the I-beams of the initial support away from the excavation side are bolted to the I-beams of the initial support on the excavation side;

[0036] 3) The mechanized demolition of the existing tunnel support structure close to the expansion side is carried out by adopting the longitudinal segmented and step-by-step demolition method.

[0037] In the aforementioned multi-section parallel tunnel expansion method, the specific steps for constructing the upper and middle steps of the circular working section on the tunnel expansion side include:

[0038] 1) The tunnel section is divided into longitudinal sections according to the designed blasting parameters, and then the corresponding blastholes are charged sequentially in the circular working area on the side of the existing tunnel;

[0039] 2) Conduct lateral micro-difference blasting, construction ventilation, and blind blast inspections sequentially. The construction ventilation adopts an exhaust ventilation mode, with ventilation ducts located within 20 meters behind the circulation work area on the tunnel expansion side. Dust generated during construction is directly extracted out of the tunnel through the ducts.

[0040] 3) Temporary mechanized support reinforcement of the existing lining structure in the existing tunnel side circulation working section to prevent the existing tunnel lining structure from becoming unstable and collapsing after being disturbed by blasting construction;

[0041] 4) Loading and transporting slag in the circular working area on the tunnel expansion side;

[0042] 5) Carry out initial support construction on the tunnel excavation side in the circular working area on the tunnel excavation side, and ensure that the end of the initial support arch on the excavation side is firmly connected to the existing tunnel structure.

[0043] Compared with the prior art, the present invention discloses a method for parallel expansion of multiple sections of a tunnel using an existing tunnel to accelerate construction. The method uses the existing tunnel as a pilot tunnel for advance construction and divides the tunnel expansion construction section into a parallel working section of the existing tunnel and a circular working section of the expanded tunnel. The parallel working section of the existing tunnel is responsible for completing the horizontal refined geological prediction of the surrounding rock around the tunnel, advance drainage, advance grouting reinforcement, and drilling construction of blastholes on the side of the tunnel expansion by arranging relevant construction equipment and work trolleys in the longitudinal direction of the existing tunnel; the circular working section of the expanded tunnel performs the construction of horizontal micro-difference blasting excavation of the surrounding rock, slag loading and transportation, mechanized demolition of the existing tunnel structure, and installation of the support structure of the expanded tunnel according to the segmented flow construction process; the relatively time-consuming surrounding rock geological prediction, surrounding rock reinforcement and blasthole drilling construction are completed in advance in the parallel working section of the existing tunnel, which cleverly reduces the number of circular construction processes in the circular working section of the expanded tunnel, significantly improving the tunnel construction safety while greatly improving the tunnel expansion construction speed, and is suitable for the renovation and expansion construction of various types of tunnels.

[0044] The beneficial effects of the present invention are:

[0045] (1) The present invention conducts multi-section short-distance lateral geological surveys in the front section of the parallel working section of the existing tunnel, and then forms a geological survey model of the surrounding rock of the tunnel based on the survey results. Compared with conventional long-distance longitudinal geological predictions, the short-distance lateral geological survey results are more accurate and have a wider detection range outside the tunnel outline, which can provide reliable geological survey data for tunnel excavation construction;

[0046] (2) The present invention can drain groundwater in advance by constructing drainage holes from the inside of the existing tunnel to the deep surrounding rock in the middle section of the parallel working section of the existing tunnel. Compared with the conventional longitudinal advance drainage holes, the transverse drainage holes have a better drainage effect on groundwater, can better achieve the drainage and consolidation effect of the surrounding rock, and effectively improve the construction environment of the tunnel excavation section. In addition, the transverse drainage holes can serve as geological drilling holes to further verify the surrounding rock conditions around the tunnel.

[0047] (3) The present invention forms a reliable surrounding rock grouting reinforcement shell around the expansion tunnel by using a skip grouting process in the middle section of the parallel working section of the existing tunnel. Since the grouting process is carried out in advance, the grouting slurry has sufficient solidification time. Its grouting reinforcement effect on the surrounding rock is far superior to tunnel advance support grouting reinforcement and system anchor reinforcement, and can replace conventional advance support and system anchor. The elimination of advance support and system anchor construction can further reduce the cyclic work intensity in the subsequent cyclic working section of the expansion tunnel, which is beneficial to speeding up the construction speed.

[0048] (4) The present invention constructs closely spaced transverse blastholes from the existing tunnel side to the tunnel expansion side in the rear section of the parallel working section of the existing tunnel and reduces the charge of each hole, and then adopts a transverse micro-difference blasting method to carry out small-charge controlled blasting excavation of the surrounding rock on the expansion side. Compared with conventional longitudinal drilling and blasting construction, the blasting energy of the transverse blastholes is mainly released along the tunnel axis to the excavation free surface. On the one hand, it can significantly improve the excavation efficiency of the surrounding rock blasting construction and greatly reduce the use of explosives. On the other hand, it can effectively reduce the disturbance and damage to the surrounding rock around the tunnel and the existing tunnel support structure. In addition, the phenomenon that the surrounding rock is thrown to the rear of the tunnel expansion direction as the blasting power increases during the blasting process is also conducive to the subsequent loading and transportation of tunnel slag;

[0049] (5) The present invention makes full use of the existing tunnel's longitudinal unobstructed construction conditions, divides the tunnel expansion construction into the existing tunnel parallel working section and the expansion tunnel circular working section, and then uses the existing tunnel parallel working section located in the front to complete the three relatively time-consuming auxiliary construction processes of geological prediction, surrounding rock advance treatment and blasthole drilling construction in advance, thereby greatly reducing the work intensity of the expansion tunnel circular working section. Compared with the conventional tunnel expansion and reconstruction construction method, it changes the logical relationship of some necessary processes from flow operation to parallel operation by adding parallel working sections, thereby effectively reducing the time required for the construction cycle in the tunnel, and achieving the effect of greatly improving the tunnel construction speed;

[0050] (6) The present invention divides the tunnel expansion section construction into five steps: excavation and support of the upper step of the surrounding rock on the expansion side, excavation and support of the middle step of the surrounding rock on the expansion side, mechanical replacement of the tunnel support structure away from the expansion side, mechanized dismantling of the tunnel support structure close to the expansion side, and excavation of the lower step of the tunnel and construction of the support structure. During the construction process, the existing tunnel structure is fully utilized as a temporary support structure during the construction process. The safety of the tunnel construction process is guaranteed by the principle of partial expansion. The whole set of construction process design is scientific and reasonable, highly operational, and has high promotion and application value.

[0051] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0053] Figure 1 The figure is a flow chart of the expansion method according to the present invention.

[0054] Figure 2 Schematic diagram of the construction working surface layout for parallel operation of related construction processes in the expansion tunnel.

[0055] Figure 3 This is the layout diagram of the short tunnel construction section (taking the exit as an example).

[0056] Figure 4 This is the layout of the middle tunnel construction section (with pedestrian tunnel).

[0057] Figure 5 This is the layout diagram of adjacent intermittent construction sections of long and extra-long tunnels (with vehicle and pedestrian tunnels).

[0058] Figure 6 Schematic diagram of the rock skipping grouting reinforcement outside the contour line of the expanded tunnel.

[0059] Figure 7 Schematic diagram of step charging blasting construction for expanding the working face.

[0060] Figure 8 Schematic diagram of the initial support construction for the steps on the excavation working surface.

[0061] Figure 9 Schematic diagram of charging and blasting construction for the middle step of the excavation working face.

[0062] Figure 10 Schematic diagram of the initial support construction for the middle step of the excavation working face.

[0063] Figure 11 Schematic diagram of the dismantling of the existing tunnel support structure away from the expansion side.

[0064] Figure 12 Schematic diagram of the initial support construction of the expanded tunnel away from the excavation side.

[0065] Figure 13 Schematic diagram of the mechanized demolition of the existing tunnel structure near the expansion side.

[0066] Figure 14 Schematic diagram of the lower excavation of the tunnel expansion and the construction of the initial support for the invert arch.

[0067] Figure 15 Schematic diagram of tunnel expansion, invert arch backfilling and secondary lining construction. DETAILED DESCRIPTION

[0068] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments are only for illustrating the present invention, and are not intended to limit the scope of protection of the present invention.

[0069] like Figures 1-15 As shown,

[0070] A method for parallel expansion of multiple sections of a tunnel by utilizing existing tunnels to accelerate construction comprises the following steps:

[0071] s1. Using the existing tunnel as a pilot tunnel for preliminary construction, the tunnel expansion construction area is divided into multiple construction sections, and within each construction section, a parallel working section for the existing tunnel and a circular working section for the expansion tunnel are divided;

[0072] s2. Carry out auxiliary construction work and preliminary preparation work before tunnel expansion in the parallel working area of ​​the existing tunnel;

[0073] s3. Carry out expansion construction simultaneously within the expansion tunnel's circular working area, including: excavation of surrounding rock for the upper and middle steps of the expansion tunnel, demolition of the existing tunnel superstructure, and construction of the initial support structure for the upper and middle steps of the expansion tunnel;

[0074] s4. In the middle section of the expanded tunnel's circular working area, the existing structure of the lower step of the expanded tunnel will be demolished and surrounding rock excavation will be carried out, and the initial support structure of the lower part of the expanded tunnel will be constructed;

[0075] s5. Construction of the expanded tunnel invert, invert backfill, secondary lining and other structures shall be carried out in the rear section of the expanded tunnel circulation working area.

[0076] Specifically, a segmented parallel construction process will be used in the front, middle, and rear sections of the existing tunnel's parallel working area for lateral geological prediction, advanced surrounding rock treatment, and blasthole drilling. In the expanded tunnel's circular working area, a segmented flow-through construction process will be used for surrounding rock excavation, slag loading and transportation, mechanized demolition of the existing tunnel structure, and construction of the expanded tunnel's support structure. Excavation slag and construction materials will be transported through the expanded tunnel to the tunnel's excavation-side circular working area. If a face collapse or support structure collapse occurs in the relevant working area during construction, construction personnel in the existing tunnel's parallel working area and the existing tunnel's side circular working area will evacuate forward in the direction of the expansion, while those in the tunnel's side circular working area will evacuate rearward in the direction of the expansion.

[0077] In step s1, multiple construction sections are set up based on the existing cross-walks for vehicles and pedestrians in the tunnel, including regular construction sections and intermittent construction sections. Construction can be organized in parallel for multiple construction sections. Specifically, for short tunnels without cross-walks for vehicles and pedestrians, only one regular construction section is set up; for medium tunnels with cross-walks for pedestrians, one regular construction section is set up at each of the tunnel's entrance and exit ends; for long or extra-long tunnels with cross-walks for vehicles and emergency lanes, in addition to one regular construction section at each of the tunnel's entrance and exit ends, intermittent construction sections can be added based on the cross-walks and emergency lanes. The number of intermittent construction sections matches the number of emergency lanes.

[0078] The intermittent construction section uses the two ends of the emergency parking strip as the excavation working surface, and the tunnel slag and engineering materials are transported to the tunnel excavation side circulation working section through the vehicle cross passage. If the relevant working surface suffers from the face collapse or the supporting structure collapse accident during the construction process, the construction personnel in the existing tunnel parallel working section and the existing tunnel side circulation working section will evacuate to another tunnel through the pedestrian cross passage in the front direction of the excavation, while the construction personnel in the tunnel excavation side circulation working section will evacuate to another tunnel through the vehicle cross passage in the rear direction of the excavation; the construction organization of the intermittent construction section should be determined in combination with the vehicle traffic conditions of the other tunnel, and the centralized transportation of tunnel slag and engineering materials should be carried out as much as possible during the time period with less traffic volume.

[0079] In step s2, with the tunnel expansion construction direction as the forward direction, the existing tunnel parallel working section is arranged in front of the expanded tunnel circular working section, and the existing tunnel parallel working section is divided into three working sections: front, middle, and rear. The work division is as follows;

[0080] (1) Conduct multi-section transverse detailed geological prediction of the tunnel surrounding rock in the front section of the parallel working section of the existing tunnel;

[0081] (2) Based on the geological prediction and exploration results, advance treatment of the surrounding rock is carried out in the middle section of the parallel working section of the existing tunnel, including lateral drainage and consolidation of the surrounding rock and grouting and reinforcement of the surrounding rock shell;

[0082] (3) Based on the geological prediction and detection results, the blasting parameters related to the horizontal micro-difference blasting are designed, and then the drilling construction of the relevant blastholes is carried out in the rear section of the parallel working section of the existing tunnel.

[0083] The specific construction details are as follows:

[0084] 1) Conducting detailed lateral geological prediction of the tunnel surrounding rock in the front section of the parallel working section of the existing tunnel;

[0085] The said horizontal refined geological prediction refers to the horizontal refined prediction of multiple longitudinal sections of the surrounding rock around the tunnel. The said prediction work can use the trolley described in "A Tunnel Lining Maintenance Trolley and Lining Defect Repair Method" (CN114046156A). The lifting platform overhead crane equipped with the above trolley is equipped with a geological radar or other surrounding rock detection equipment to perform short-range precise detection of the surrounding rock around the tunnel. Through the short-range geological detection results with equal spacing in multiple cross sections, a relatively accurate geological detection model of the surrounding rock around the tunnel can be formed.

[0086] The detection range is 10 to 15 meters outside the tunnel contour line. Preferably, the upper limit value is taken for the detection distance on the excavation side, and the lower limit value is taken for the detection distance away from the excavation side.

[0087] Compared to conventional long-distance longitudinal geological surveys, short-distance horizontal geological surveys provide a wider coverage of the surrounding rock mass of the tunnel contour and higher accuracy. This provides reliable surrounding rock information for tunnel construction and effectively prevents tunnel construction accidents caused by sudden geological changes. Furthermore, if questions about the surrounding rock mass remain after surveying, radial geological drilling can be conducted from the side of the existing tunnel toward the surrounding rock mass for further investigation.

[0088] 2) Based on the geological prediction and detection results of the tunnel surrounding rock, advanced surrounding rock treatment construction such as transverse drainage consolidation and radial jump grouting is carried out in the middle section of the parallel working area of ​​the existing tunnel;

[0089] Since the geological prediction and detection work is far ahead of the circulating working section on the tunnel expansion side, when water-rich surrounding rock is detected, drainage holes can be constructed in the middle section of the parallel working section of the existing tunnel from the inside of the existing tunnel to the deep surrounding rock to drain the groundwater in advance, so as to improve the construction environment of the subsequent excavation face; at the same time, grouting holes are drilled in the middle section of the parallel working section of the existing tunnel from the inside of the existing tunnel to the deep surrounding rock, and radial jump grouting is carried out on the surrounding rock outside the contour line of the expanded tunnel.

[0090] Radial skip grouting refers to grouting reinforcement of the surrounding rock outside the expanded tunnel without grouting the surrounding rock within the expanded tunnel. This method forms a reliable surrounding rock grouting reinforcement shell outside the excavation contour before tunnel excavation. Because this grouting construction significantly precedes tunnel excavation, the grouting slurry has sufficient time to set, and skip grouting provides a reliable slurry sealing section. Therefore, this grouting effect is excellent, and the surrounding rock reinforcement effect is far superior to tunnel advance support reinforcement and system anchor reinforcement, and can replace conventional advance support and system anchor construction. Eliminating advance support and system anchor construction can further reduce the construction steps within the expanded tunnel's cyclic working area, speeding up the construction cycle and contributing to a faster construction speed.

[0091] Radial jumping grouting construction can use conventional grouting technology: by driving grouting pipes of different lengths into the surrounding rock and setting grouting stop sections of different lengths at the end of the grouting pipes, the radial jumping grouting effect can be achieved.

[0092] 3) Based on the known surrounding rock conditions of the tunnel expansion side, blasting parameters for horizontal micro-difference blasting are designed, and then relevant blastholes are drilled in the rear section of the parallel working section of the existing tunnel;

[0093] Since the blasthole is drilled in advance, a casing can be inserted into the blasthole to prevent it from collapsing due to the vibration of tunnel blasting;

[0094] If the positions of the horizontal drainage holes and grouting holes drilled in the early stage are suitable, they can be used directly as blast holes to reduce the workload of blast hole construction; if the positions are not suitable, they can be used as shock-absorbing holes for blasting construction.

[0095] The blasting parameters related to transverse micro-difference blasting are designed as follows: the blastholes are arranged in a plum blossom shape with equal spacing in the circumferential and longitudinal directions. The specific spacing is determined according to the surrounding rock conditions on site. Since the blasthole drilling process has no effect on the construction of the circulating working area on the tunnel expansion side, the blasthole spacing can be increased and the amount of explosives per hole can be reduced.

[0096] In step s3, with the tunnel excavation construction direction as the forward direction, the expanded tunnel circulation work section is divided into three working sections: front, middle, and back. The front section of the expanded tunnel circulation work section is further subdivided into the existing tunnel side circulation work section and the tunnel excavation side circulation work section. The work division is as follows:

[0097] (1) Using an alternating construction method, the upper and middle steps of the tunnel expansion side circulation working area are sequentially carried out with explosive blasting, slag loading and transportation, and initial support construction;

[0098] (2) Carry out mechanized dismantling of the tunnel support structure away from the expansion side in the existing tunnel side circulation working section;

[0099] (3) Carry out initial support construction away from the excavation side in the existing tunnel side circulation working section, and connect the initial support on the excavation side and the side away from the excavation side together;

[0100] (4) Carry out mechanized demolition of the tunnel support structure close to the expansion side in the circulation work section on the existing tunnel side.

[0101] The specific construction details are as follows:

[0102] 1) The tunnel section is divided into longitudinal sections according to the designed blasting parameters. The blasting section adjacent to the tunnel expansion side circular working section in the existing tunnel side circular working section is divided into upper and middle steps for blasthole charging;

[0103] Blasthole charging and blasting construction: Charge is only charged in the middle and rear sections of the blasthole, and the front section is filled with blasthole mud to seal the blasthole. This charging design can reduce the disturbance and damage caused by blasting construction to the existing tunnel structure; the detonation sequence is set to micro-difference detonation, first detonating the upper blastholes of the first ring, and then successively detonating the middle and lower blastholes of the first ring; after the first ring is blasted, the next ring of blastholes is detonated successively according to the above rules; the number of blastholes to be detonated at a time should be determined according to the surrounding rock conditions. If the surrounding rock is relatively stable, one or two more rings can be blasted, but a maximum of three rings of blastholes can be blasted at a time to ensure sufficient open surface for each blast. At the same time, the energy of the lateral blasting is mainly released to the rear of the open surface, throwing the surrounding rock to the rear along the direction of tunnel expansion, which is conducive to the subsequent loading and transportation of tunnel slag.

[0104] 2) After evacuating the construction personnel and equipment near the area to be blasted, carry out horizontal micro-difference blasting, construction ventilation, blind blast inspection and other related work in sequence on the upper and middle steps;

[0105] First, blasting construction is carried out on the upper steps of the circular working section on the tunnel excavation side. After the tunnel slag is loaded, initial support construction is carried out on the newly excavated surrounding rock surface on the upper steps of the circular working section on the tunnel excavation side. The upper end of the initial support for the newly excavated surrounding rock surface should be tightly connected to the existing tunnel lining structure through shotcrete, and the upper end of the initial support should be grouting connected to the arch surrounding rock through grouting pipes. By supporting the initial support on the existing tunnel support structure, it can effectively prevent adverse deformation of the initial support under the pressure of the surrounding surrounding rock after construction. Subsequently, similar to the construction steps for the upper steps, blasting construction and initial support construction are carried out on the middle steps of the circular working section on the tunnel excavation side.

[0106] Construction ventilation: exhaust ventilation should be adopted, and the ventilation pipe should be arranged within 20 meters behind the circulation working area on the tunnel expansion side, so that the dust generated during the construction process can be directly extracted out of the tunnel through the air duct.

[0107] Since the parallel working section of the existing tunnel in front and the side circulation working section of the existing tunnel and the side circulation working section of the tunnel expansion are offset by a large distance in the longitudinal direction of the tunnel, the mutual interference between the construction processes is very small. Therefore, except for the tunnel charging, detonation and construction ventilation processes, the relevant construction in the parallel working section of the existing tunnel can be carried out continuously and uninterruptedly.

[0108] Excavation slag transportation: Excavation slag from regular construction sections is loaded onto trucks by excavators and transported to the rear in the direction of excavation expansion. Excavation slag from intermittent construction sections is loaded onto trucks by excavators, then driven through the crosswalk to another tunnel by dump trucks for transportation outside the tunnel. When transporting construction materials or slag through the crosswalk, traffic within the tunnel must be controlled to ensure driving safety.

[0109] 3) Carry out temporary mechanical support reinforcement work on the existing tunnel support structure in the existing tunnel side circulation working area;

[0110] Temporary mechanical support and reinforcement of existing tunnel lining structures: Due to the disturbance caused by blasting construction, the existing tunnel lining structure in the existing tunnel side circulation working section may have local cracks. Relevant mechanical equipment should be used for temporary support and reinforcement to prevent the existing tunnel lining structure from becoming unstable and collapsing. The relevant mechanical equipment can use the trolley described in "A Tunnel Lining Maintenance Trolley and Lining Defect Repair Method" (CN114046156A), and the folding arc steel support mechanism and the retractable arc maintenance support mechanism equipped on the trolley can be used to provide temporary mechanical support for the existing tunnel lining structure.

[0111] 4) Carry out mechanized dismantling of the tunnel support structure in the existing tunnel side circulation working section close to the expansion side;

[0112] Mechanized demolition of the existing tunnel support structure away from the expansion side: the trolley described in "A Tunnel Lining Inspection Trolley and Lining Defect Repair Method" (CN114046156A) can be used. The grinding wheel cutter is mounted on the lifting platform overhead crane equipped with the above trolley to remove the existing tunnel lining structure away from the expansion side in blocks. Since a reliable surrounding rock grouting reinforcement shell has been formed on the outside of the expanded tunnel, the external surrounding rock can remain stable after the demolition of the existing tunnel structure. After the demolition is completed, the tunnel excavation section is trimmed, and the initial support away from the expansion side is constructed in a timely manner. The I-beams of the initial support away from the expansion side are connected one by one with the I-beams of the initial support on the expansion side, and the joints are connected with bolts.

[0113] 5) Mechanized demolition of the tunnel support structure near the excavation side: The trolley described in "A Tunnel Lining Inspection Trolley and Lining Defect Repair Method" (CN114046156A) can continue to be used, and the grinding wheel cutter can be installed on the lifting platform crane (703) equipped with the above trolley to cut the tunnel support structure near the excavation side in blocks. When demolishing the tunnel support structure near the excavation side, the displacement monitoring of the initial support structure of the expansion tunnel should be strengthened, and the demolition should be carried out in longitudinal sections and sections at a time to ensure the stability of the initial support structure of the expansion tunnel. The continuous demolition section of the tunnel support structure near the excavation side should not be too long. After demolition, the construction of subsequent processes should be organized as soon as possible, and the secondary lining should be constructed in a timely manner.

[0114] In steps 4 and 5, existing construction techniques are used to demolish the existing structure and excavate the surrounding rock below the expansion tunnel, followed by the construction of the initial support structure below the expansion tunnel.

[0115] The construction of the expanded tunnel invert, invert backfill, secondary lining and other structures was carried out, thus completing the construction of a section of the expanded tunnel.

[0116] The above description is only a preferred embodiment of the present invention and does not constitute any form of confidentiality restriction on the present invention. Any simple modification, equivalent change and modification of the above embodiment that does not deviate from the content of the technical solution of the present invention and is 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 method for parallel expansion of multiple sections of a tunnel by accelerating construction using an existing tunnel, characterized in that: The following steps are involved: s1. Using the existing tunnel as a pilot tunnel for preliminary construction, the tunnel expansion construction area is divided into multiple construction sections, and within each construction section, a parallel working section for the existing tunnel and a circular working section for the expansion tunnel are divided; s2. Carry out auxiliary construction work and preliminary preparation work before tunnel expansion in the parallel working area of ​​the existing tunnel; s3. Carry out expansion construction simultaneously within the expansion tunnel's circular working area, including: excavation of surrounding rock for the upper and middle steps of the expansion tunnel, demolition of the existing tunnel superstructure, and construction of the initial support structure for the upper and middle steps of the expansion tunnel; s4. In the middle section of the expanded tunnel's circular working area, the existing structure of the lower step of the expanded tunnel will be demolished and surrounding rock excavation will be carried out, and the initial support structure of the lower part of the expanded tunnel will be constructed; s5. Construction of the expanded tunnel invert, invert backfill, secondary lining and other structures in the rear section of the expanded tunnel circulation working area; In step s2, with the tunnel expansion construction direction as the forward direction, the existing tunnel parallel working section is arranged in front of the expanded tunnel circular working section, and the existing tunnel parallel working section is divided into three working sections: front, middle, and rear. The work division is as follows; (1) Conduct multi-section transverse detailed geological prediction of the tunnel surrounding rock in the front section of the parallel working section of the existing tunnel; (2) Based on the geological prediction and exploration results, advance treatment of the surrounding rock is carried out in the middle section of the parallel working section of the existing tunnel, including lateral drainage and consolidation of the surrounding rock and grouting and reinforcement of the surrounding rock shell; (3) Based on the geological prediction and exploration results, the blasting parameters related to horizontal micro-difference blasting are designed, and then closely spaced horizontal blastholes are constructed from the side of the existing tunnel to the side of the tunnel expansion in the rear section of the parallel working section of the existing tunnel; In step s3, with the tunnel excavation construction direction as the forward direction, the expanded tunnel circulation work section is divided into three working sections: front, middle, and back. The front section of the expanded tunnel circulation work section is further subdivided into the existing tunnel side circulation work section and the tunnel excavation side circulation work section. The work division is as follows: (1) Using an alternating construction method, the upper and middle steps of the tunnel expansion side circulation working area are sequentially carried out with explosive blasting, slag loading and transportation, and initial support construction; (2) Carry out mechanized dismantling of the tunnel support structure away from the excavation side and initial support construction in the circulation working section on the existing tunnel side, and connect the initial support on the excavation side and the side away from the excavation side together; (3) Carry out mechanized demolition of the tunnel support structure close to the expansion side in the circulation working section on the existing tunnel side.

2. The method for parallel expansion of multiple sections of a tunnel using an existing tunnel for accelerated construction according to claim 1, characterized in that: In the front, middle and rear sections of the parallel working area of ​​the existing tunnel, the horizontal detailed geological forecast, advanced treatment of surrounding rock and blasthole drilling construction are carried out according to the segmented parallel construction process; in the circulating working area of ​​the expanded tunnel, the surrounding rock excavation, slag loading and transportation, mechanized demolition of the existing tunnel structure and construction of the expanded tunnel support structure are carried out according to the segmented flow construction process.

3. The method for parallel expansion of multiple sections of a tunnel using an existing tunnel for accelerated construction according to claim 2, characterized in that: In step s1, the construction sections are set up in plurality according to the layout of existing vehicle and pedestrian cross passages in the tunnel, and include regular construction sections and intermittent construction sections; construction is organized in parallel in the plurality of construction sections.

4. The method for parallel expansion of multiple sections of a tunnel using an existing tunnel for accelerated construction according to claim 3, characterized in that: For short tunnels without pedestrian cross passages, only one conventional construction section is arranged; for medium tunnels with pedestrian cross passages, one conventional construction section is arranged at the tunnel entrance and exit ends; for long or extra-long tunnels with pedestrian cross passages and emergency parking lanes, in addition to one conventional construction section at the tunnel entrance and exit ends, intermittent construction sections are added based on the pedestrian cross passages and emergency parking lanes, and the number of intermittent construction sections matches the number of emergency parking lanes.

5. The method for parallel expansion of multiple sections of a tunnel by accelerating construction using an existing tunnel according to claim 1, characterized in that: Specifically include: 1) Based on the results of short-distance geological exploration at multiple longitudinal sections of the tunnel, a relatively accurate geological exploration model of the surrounding rock mass around the tunnel is formed; 2) When geological detection indicates that the surrounding rock is rich in water, drainage holes are constructed in the middle section of the parallel working section of the existing tunnel from the interior of the existing tunnel to the deep surrounding rock to drain the groundwater in advance, thereby improving the construction environment in the tunnel excavation section. At the same time, grouting holes are drilled in the middle section of the parallel working section of the existing tunnel from the interior of the existing tunnel to the deep surrounding rock to grout the surrounding rock outside the outline of the expansion tunnel. This will form a reliable surrounding rock grouting reinforcement shell outside the excavation outline of the expansion tunnel before the surrounding rock excavation begins. 3) In the rear section of the parallel working area of ​​the existing tunnel, drilling construction of relevant blastholes is carried out into the surrounding rock of the expanded excavation side in a dense longitudinal arrangement.

6. The method for parallel expansion of multiple sections of a tunnel by accelerating construction using an existing tunnel according to claim 5, characterized in that: Specifically include: 1) The horizontal refined geological prediction detection range is 10 to 15 meters outside the existing tunnel outline; 2) By using grouting pipes of different lengths and setting grouting stops of different lengths at the ends of the grouting pipes, a radial skipping grouting effect is achieved, whereby only the surrounding rock outside the outline of the expanded tunnel is reinforced by grouting without grouting within the expanded tunnel. 3) Drill blastholes in advance and insert casings into them to prevent them from collapsing due to the vibration of tunnel blasting. If the horizontal drainage holes and grouting holes drilled in the early stage are in the right positions, they can be used directly as blastholes to reduce the workload of blasthole construction.

7. The method for parallel expansion of multiple sections of a tunnel by accelerating construction using an existing tunnel according to claim 1, characterized in that: Specifically include: 1) First, blasting construction is carried out on the upper steps of the circular working area on the tunnel expansion side. After the slag is loaded and transported, the initial support of the relevant sections is carried out in a timely manner. Then, blasting excavation, slag loading and transportation, and initial support construction are carried out on the middle steps of the circular working area on the tunnel expansion side. Loading the gun: charging the middle and rear sections of the blasthole, and filling the front section with gun mud to seal the blasthole; The detonation sequence is set to micro-difference detonation: first detonate the upper blastholes of the first ring, then successively detonate the middle and lower blastholes of the first ring; after the first ring is blasted, detonate the next ring of blastholes in the same order; the number of blastholes to be detonated at one time should be determined according to the surrounding rock conditions; if the surrounding rock is relatively stable, one or two more rings should be blasted, but a maximum of three rings of blastholes can be blasted at one time to ensure that there is sufficient open space for each blast; at the same time, the energy of the lateral blasting is mainly released in the direction with open space, throwing the surrounding rock backward along the tunnel expansion direction; 2) The existing tunnel lining structure away from the excavation side is removed in sections, and then the tunnel excavation section is trimmed. The initial support structure away from the excavation side is constructed in a timely manner, and the I-beams of the initial support away from the excavation side are bolted to the I-beams of the initial support on the excavation side; 3) The mechanized demolition of the existing tunnel support structure close to the expansion side is carried out by adopting the longitudinal segmented and step-by-step demolition method.

8. The method for parallel expansion of multiple sections of a tunnel by accelerating construction using an existing tunnel according to claim 7, characterized in that: The specific steps for constructing the upper and middle steps in the circular working area on the tunnel expansion side include: 1) The tunnel section is divided into longitudinal sections according to the designed blasting parameters, and then the corresponding blastholes are charged sequentially in the circular working area on the side of the existing tunnel; 2) Conduct lateral micro-difference blasting, construction ventilation, and blind blast inspections sequentially. The construction ventilation adopts an exhaust ventilation mode, with ventilation ducts located within 20 meters behind the circulation work area on the tunnel expansion side. Dust generated during construction is directly extracted out of the tunnel through the ducts. 3) Temporary mechanized support reinforcement of the existing lining structure in the existing tunnel side circulation working section to prevent the existing tunnel lining structure from becoming unstable and collapsing after being disturbed by blasting construction; 4) Loading and transporting slag in the circular working area on the tunnel expansion side; 5) Carry out initial support construction on the tunnel excavation side in the circular working area on the tunnel excavation side, and ensure that the end of the initial support arch on the excavation side is firmly connected to the existing tunnel structure.

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