LU502525B1 - A Method for Centralizing TBM Segments - Google Patents

Abstract

The invention belongs to the technical field of tunneling, and in particular relates to a method for centralizing TBM segments. The 3-6 ring segments are provided with a ring of hoses, and each ring of hoses is formed by splicing several small hoses which adapt to the arc length of segments together; Install the small hose on the segment from the bottom arch, and the I-beam is arranged in the small hose at the bottom; With the assembly of segments, fill the hose into the gap between the excavated section and segments; When the standard block segments on both sides are assembled, inject high-strength quick-setting cement slurry into the small hose at the bottom arch, At the same time, grout is poured into the small hoses on both sides, and after the hoses are completely spliced along with the segment assembly, grout is injected into the small hoses at the adjacent block and the capping block. According to the invention, the installation of the TBM segments has the function of keeping the alignment and straightening, and the pouring amount of each unit can be quantitatively calculated through the separation of the hose consolidation bodies, so that the process of bleeding and grouting the inflatable grout stop pipe is reduced.

Description

DESCRIPTION

A Method for Centralizing TBM Segments LU502525

FIELD OF THE INVENTION

The invention belongs to the technical field of tunneling, and particularly relates to a method for centralizing TBM segments.

BACKGROUND OF THE RELATED ART

TBM has been widely used in tunnel construction because of its advantages of high tunneling speed and high safety performance. To ensure the construction quality and safety,

TBM has many important construction processes. Among them, the backfill and grouting of pisolite is an important link in TBM construction.

A large number of engineering practices have proved that there are many problems in the backfill and grouting technology of pisolite, and the most prominent one is the abnormal grouting amount of cement slurry behind the pipe. In construction technology, because the diameter of cutter head excavation is larger than the diameter of segment, when the cutter head exerts a reaction force on segment, segment will produce a swinging effect in the cave wall, resulting in an extremely exhausted area between segment and excavation section. Due to the swinging of the tube, it is difficult to pour the pea stone and form a cavity. The grouting amount of cement slurry in the cavity increases, and the over-grouting amount is much larger than the design, which affects the subsequent grouting effect and greatly reduces the support quality.

Such as Liu Liping. Construction method of full-face roadheader [P]. Shanxi:

CN1166852C, 2004-09-15. The technical solutions include: Technology of cutting rock and lining segments, in which: It also includes the technology of segment water stopping, backfilling bean stone and pouring cement slurry; The segment water-stopping process consists of the following steps: butt-joint precast reinforced concrete segments according to the design requirements; Placing the filling strip on the butt joint at the bottom of the filling groove formed between the segments, Embedding plastic water-stop material into the filling tank until it is filled; Wedge an iron wedge from the top of the filling tank to compress the plastic water-stop material; Backfilling the butt joint gap of the segment surface with high- strength cement mortar, and configuring several lead wires; When the pea stone is backfilled and cement slurry is poured between the surrounding rock and the segments, part of the cement slurry is injected into the butt joint between the two segments; The process of 1 backfilling beanstalk and pouring cement slurry consists of the following steps: Segmenting LU502525 the periphery of the installed segment by 12-20m, and circumferentially arranging rubber hoses at the periphery of the segmented segment; Fill the rubber hose with gas with a pressure of 0.2MPa, so that the rubber hose expands and presses on the rock wall and the segment;

Backfilling the periphery of the segmented segments with pea stones; Grouting; After the cement slurry is solidified, finally deflate the rubber hose and pour the cement slurry, thereby achieving the purposes of segment water stopping and bean stone backfilling in sections.

In this technology, the inflatable slurry-stopping pipe is used to segment the periphery of the segment. It can be found that the whole formed by the inflatable ring and the segment cannot balance the axial thrust generated during TBM cutting to a certain extent because of the low air pressure intensity in the inflatable pipe, and can't achieve the functions of fixing the segment and keeping it upright. At the same time, it is precisely because of the insufficient air pressure strength of the inflatable grout stop pipe that the gravity of the segment itself is large, and all the gravity of the segment itself will be transferred to the inflatable grout stop pipe at the bottom. Although the inflatable grout stop pipe can meet certain requirements in compressive strength and ensure the tightness, it is bound to be compressed, and the center of the segment is not concentric with the center of the cross section. In the section with large axial thrust, it is likely to form an extremely close area, resulting in a decrease in the backfill amount of pea gravel and an increase in the grouting amount. In addition, where the TBM trajectory design needs to turn, a component of the axial thrust of TBM will squeeze the inflatable slurry-stopping pipe on the side wall of the turn, causing the inflatable slurry- stopping pipe to compress, As the inflatable grout-stopping pipe is inflated and sealed after being placed, the inflatable pipe on one side of the side wall is compressed and the segment is displaced to a certain extent, and the inflatable pipe on the other side wall changes from the state of being close to the rock wall to a certain gap with the rock wall, which leads to grout leakage during grouting in this interval and increases the grouting amount of cement slurry. In addition, the installation spacing of the inflatable slurry stop pipe is too large, so it can't meet the requirement of resisting axial thrust. Therefore, the disadvantages of this technology are: (1) The strength of air pressure can't meet the requirement of straightening, and it can still form the extreme zone in the construction process, resulting in the increase of grouting quantity. (2) After backfilling the beanstalk, it is necessary to deflate the inflatable slurry- stopping pipe, and then backfill to increase the construction steps.

Shi Xuantao, Lin Gang, Zhang Jianxiang, etc. An inverted arch support assembly suitable for shield TBM tunnel precast segment lining structure [P]. Sichuan: CN108005680A, 2

2018-05-08. The technical solution includes: On the premise of not weakening the structural LY502525 performance of segments, it can effectively solve the problem of natural subsidence of lining segments when they come off the shield tail, greatly improve the ring quality of segments, and at the same time facilitate the installation of segments and ensure the waterproof performance of the structure. The thread sleeve is arrange in that outer structure of the prefabricate segment according to the envelope of the assembling point; The inverted arch support member is symmetrically arranged at the outer side of the lower part of the inverted arch, and is provided with inverted arch support legs and support screws, and the support screws are detachably connected with the threaded sleeves. In the process of implementation, four rows of eight threaded sleeves are set for the precast segments of the bottom arch and two inverted arches according to the envelope of the assembling points of these segments, so that the installed two rows of four inverted arch support members are symmetrically arranged along the vertical centerline of the segments. Among them, the threaded sleeve should be embedded in the production process of precast lining segments, and the port of the threaded sleeve should be temporarily blocked to prevent the segments from being blocked by cement mortar during the casting process. After the precast segments are completed, the blocking will be chiseled out.

In the process of segment installation, this technology prevents the segment from sinking naturally through the support of threaded sleeve and inverted arch support members. However, it can be found that the installed members can't form a multi-section closed space, which can't realize the segmented backfilling of pea stones. In addition, because the strength of this group of components is limited, it is necessary to install this component in each ring segment to bear the segment's self-weight. At the same time, due to the different splicing forms of segments, this group of components has two forms in structural design, which increases the construction difficulty.

SUMMARY OF THE INVENTION

The invention provides a method for centralizing TBM segments . The core of centralizing segments is to limit the vertical displacement of segments and ensure that the center of segments is concentric with the center of excavation section.

The specific technical scheme is as follows:

The TBM segments segment centralizing method comprises the following steps:

A. Segment the interval for installing segments reasonably, and 3-6 segments can be installed with a ring of hoses, each ring of hoses is composed of several segments of small hoses suitable for segment arc length. 3

B. On the segment that needs to be installed with hoses, install small hoses on the LUS02525 segment from the bottom arch, and I-beam is arranged in the small hose at the bottom, and the

I-beam in the small hose at the bottom fills the gap between the excavation section and the segment, and plays a role in supporting the upper segment at the same time;

C. According to the installation sequence of segments, continue to install small hoses on segments, and with the assembly of segments, fill the hoses into the gap between the excavated section and segments;

D. When the standard segments on both sides are assembled, inject high-strength quick- setting cement slurry into the small hose at the bottom arch, and block the grouting hole after the injection; At the same time, grout is poured into the small hoses on both sides to ensure symmetry as much as possible.

E. Continue to assemble the segments and hoses. After the hoses are completely spliced with the segments, grout into the small hoses at the adjacent block and the capping block.

After the grouting is completed, the grouting holes need to be blocked.

The method for centralizing the TBM segments provided by the invention has the function of maintaining the alignment and straightening for the installation of TBM segments, and avoids the formation of an extremely close area between the segments and the excavation section, thus reducing the backfill amount of pea gravel and increasing the grouting amount.

In addition, the segment interval is artificially divided into several independent intervals by the partition of the hose consolidation body, which ensures the segmented backfilling of the pea stone, and then the grouting quantity of each unit can be quantitatively calculated. If the grouting quantity is far greater than the design value, the abnormal grouting quantity caused by other factors can be considered and analyzed. At the same time, because the distance between hoses is not long, if the abnormal grouting quantity is found in this interval, it is also convenient to analyze the specific problems in a certain position or a small section, which leads to the abnormal grouting quantity, so as to solve the problems conveniently and pertinently. In addition, since the installed hose has high strength after being injected with cement slurry, it does not need to be taken out, which reduces the process of deflation and grouting of the inflatable grout stop pipe, and saves the time cost to a certain extent.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of vertical displacement of segments;

Fig. 2 is a schematic diagram of bending displacement of the beam; 4

Fig. 3 is a schematic diagram of statically indeterminate structure; LU502525

Fig. 4 is a cross-sectional view of the x-direction projection of a section of this embodiment after the centralizing measures are taken;

Fig. 5 is a schematic cross-sectional structure diagram of the small hose of this embodiment;

Fig. 6a is a schematic diagram of the centering of segment A;

Fig. 6b is a cross-sectional view of the small hose with the A segment centered,

Fig. 7a is a schematic structural diagram of a tube piece rotating at a certain angle;

Fig. 7b is a cross-sectional view of the small hose in the state that the segment rotates at a certain angle;

Fig. 8 is the splicing diagram of segments;

Fig. 9 shows the details of the central area of the grouting hole;

Fig. 10 is a structural schematic diagram of pipe embedded parts and hose connectors in this embodiment;

Fig. 11 is a projection view of this embodiment after the hose is installed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The specific technical scheme of the invention will be explained with embodiments.

In the process of TBM tunneling, there is a gap between the segment and the excavated section. Due to the vertical force such as the segment's self-weight, the segment is vertically displaced, resulting in the segment being not concentric with the excavated section, as shown in Figure 1. Under the action of the axial thrust generated by TBM, the radial displacement of the segment is caused by the eccentric relationship between the position of the axial thrust and the center of the cross section, resulting in the extremely close area. Therefore, the core of centralizing the segment is to limit the vertical displacement of the segment and ensure that the center of the segment is concentric with the center of the excavation section.

The vertical displacement of segments is limited by installing hoses on the periphery of segments, grouting them, and using the consolidation strength in the hoses to resist vertical forces such as segment self-weight, so as to ensure that the center of segments is concentric with the center of excavation section. Under the action of axial thrust, the extremely close area can be prevented. At the same time, it also ensures the sealing property of the segmented interval, so as to realize the segmented backfilling of the pea stone and ensure the pouring amount of cement slurry.

Without considering the effect of soil or surrounding rock around segments on segments LUS02525 and the effect of connecting bolts between segments, the stress of a segment can be simplified as the stress of a beam. Aiming at the requirements of this problem, the bending stiffness of the beam is mainly analyzed.

In the segment interval between filled and unfilled pisolite, the segment in this interval can be regarded as a cantilever beam model, in which the self-weight and other vertical forces of the segment can be converted into distributed forces acting on the cantilever beam, so as to discuss the bending displacement of the beam, as shown in Figure 2.

According to the calculation formula of the rotation angle (0) and the maximum deflection ( max) of the uniformly distributed load on the cantilever beam:

Among them: q- uniformly distributed load; I- beam length; e- elastic modulus; i- moment of inertia; ei- bending stiffness

Through the above formula, it can be found that the rotation angle of the beam is proportional to the cubic power of the beam length, and the deflection of the beam is proportional to the fourth power of the beam length. Therefore, with the continuous splicing of segments, that is, the continuous increase of cantilever beam length, the angle and maximum deflection of cantilever beam will also increase at this time, resulting in large displacement. This is the reason why the segment sinks when the centralizing method is not taken.

Therefore, in order to reduce the angle and maximum deflection of the beam, the length of the beam can be reduced, the moment of inertia can be increased or the stiffness of the beam can be increased when the external uniform load is certain. It can be found that when segments are spliced, the bending stiffness of segments is constant, while the cross-sectional shape of segments is constant, that is, the moment of inertia is constant. With the assembly of segments, the length of segments keeps increasing. Therefore, when the stiffness and moment of inertia are constant, and the length of the beam cannot be reduced, the method of adding intermediate supports is considered to increase the bending stiffness of the beam, that is, the statically indeterminate structure is adopted. As shown in Figure 3, the cantilever beam with statically determinate structure is changed into a statically indeterminate beam with redundant constraints, which can greatly reduce the maximum bending moment of the beam and significantly improve the bending deformation of the beam under external load.

Therefore, the core of the centralizing principle of the invention is to change the statically determinate structure of the segment into a statically indeterminate structure by 6 installing intermediate constraints, so as to improve the bending rigidity of the segment and LY902525 achieve the purpose of limiting the vertical displacement of the segment.

The specific technical scheme includes the following steps:

A. Segment the interval for installing segments reasonably, and 3-6 segments can be installed with a ring of hoses, each ring of hoses is composed of several segments of small hoses suitable for segment arc length.

B. On the segment that needs to be installed with hoses, install small hoses on the segment from the bottom arch, and I-beam is arranged in the small hose at the bottom, and the

I-beam in the small hose at the bottom fills the gap between the excavation section and the segment, and plays a role in supporting the upper segment at the same time;

C. According to the installation sequence of segments, continue to install small hoses on segments, and with the assembly of segments, fill the hoses into the gap between the excavated section and segments;

D. When the standard segments on both sides are assembled, inject high-strength quick- setting cement slurry into the small hose at the bottom arch, and block the grouting hole after the injection; At the same time, grout is poured into the small hoses on both sides to ensure symmetry as much as possible.

After the slurry in the hose reaches the predetermined strength, the annular consolidated body can be called the centralizing ring. Figure 4 is a cross-sectional view of x-direction projection after the centralizing measures are taken in a certain section.

The centralizing method adopts a hose with a certain diameter and high strength (meeting the design strength requirement). In order to make the hose reach the designed strength in a short time, it is considered to embed and weld metal strips with a certain diameter in the hose, and the metal strips form a certain included angle on the inner wall of the hose; The metal strips can be steel bars or other alloy strips, and grouting can be carried out after the hose is installed to meet the use requirements.

The metal strip installed in the hose is small in diameter or width, and short in length.

Because its material itself has hardness and strength, its inclination angle should not be too large when it is welded to the hose. The metal strips are not connected with each other, and there is a channel for slurry circulation, which can adapt to the change of the gap between the segment and the surrounding rock, as shown in Figure 5. In addition, the middle of the small hose is provided with a hose connector, which will be introduced later.

In addition, in the hose at the bottom of the whole segment, on the basic hose structure,

I-beam structure needs to be added in the hose. The I-beam equipped with the bottom arch 7 hose can support the whole segment when the injected cement slurry has no strength. In LU902525 addition, before the segments are assembled, the height difference between the left and right of the previous segment should be measured by the surveyors. If the measured left side is high, then the bottom falling block of the next ring will rotate to the right side correspondingly during assembly, and finally the bottom falling block will be centered and almost the same height at both ends. Therefore, the position of I-beam in the hose at the bottom should have two forms to adapt to the change of the relative position of segments.

As shown in fig. 6a, when segment A is centered, as shown in fig. 6b, two I-beams are arranged in the hose under segment A, and their placement positions are set longitudinally along the excavation direction; As shown in Figure 7a, when segment A needs to rotate to the right (or left) for installation, there is only one I-beam in the hose under segment A, and as shown in Figure 7b, the hose under segment B2 (or B1) will also be installed with one I-beam, and the I-beam is longitudinally arranged along the excavation direction.

In most cases, it is impossible for the bottom block to be completely centered, so it is often the case to rotate left or right for installation. However, no matter whether the bottom block is centered or not, after the standard blocks B1 and B2 are installed, due to the segmented sealing of the hoses behind the segments, it is considered that grouting should not be carried out after the segments are completely installed. The bottom block and the standard block can be grouted first, so that the bottom has strength as soon as possible, and the self- weight of the upper segments can be shared. The purpose is to reduce the I-beam's self-weight pressure on the segment alone, reduce the difficulty of material selection and structural design of I-beam in the later period, and the most important thing is to lower the manufacturing cost of I-beam. It should be noted that the height of I-beam is fixed because of its invariable structure. When designing, the difference between TBM excavation section and segment outer diameter should be considered to design the height of I-beam. Before installation, the rock wall should also be cleaned, which is conducive to the fixation of I-beams. In addition, if the commonly used I-beam model is selected according to the height of I-beam, it may not meet the engineering requirements. According to the compression condition of I-beam, the waist thickness, leg width and other parameters should be set reasonably.

As for the connection between the hose and the segment, since the segments are spliced from bottom to top in turn, as shown in Figure 8, it is not a whole hose that is connected at the periphery of the segment, but a ring is connected by segments.

Step 1: assemble the bottom block; Step 2: assemble the standard block; Step 3: assemble adjacent blocks; Step 4: Assemble the back cover block; 8

Each section of hose is installed on the segment in advance, and the segment is LU502525 assembled into a ring. In order to realize the assembly of hoses into rings along with the installation of segments, the available structure of segments can be considered first.

Figure 9 shows the details of the central area of the grouting hole. According to the structure of the segment itself, it is considered to set a hose connector at the center of each segment of hose to connect with the grouting hole in the center of the segment. The function of this device is positioning, and the other is that it is the channel for grouting into the hose after installation. When the pipe is installed, a pipe embedded part is usually installed at the position of the grouting hole to realize post-grouting of the pipe. Therefore, it is considered to adjust the partial structure of the general grouting hole pipe embedded parts to realize the connection between the segment and the hose. In the structural adjustment, it is considered that the smooth end of the embedded part of the general grouting hole pipe should be processed with a certain size of external thread, and then connected with the internal thread of the hose connector to realize the connection and fixation of the grouting channel, as shown in

Figure 10.

The length of the processed pipe embedded parts is shorter than that of the common ones, so as to adapt to the connection between the hose connector and the pipe embedded parts by entering the grouting hole, and to ensure that the hose and the segment can fit together after connection.

In addition, because the hose itself has a certain gravity, if the hose is fixed only by the connecting device in the central position, it will sink under the action of the hose's own gravity during the installation process, and the joint between the hose and the segment cannot be realized. Therefore, it is considered to apply super glue to the part where the hose is in contact with the segment and fix the hose on the segment.

After the hose is installed along with the splicing of segments, inject high-strength quick- setting cement slurry meeting the design requirements into the hose through the grouting hole.

The cement slurry and steel bar or other hard alloy in the pipe form a consolidated body, which should meet the strength requirement of resisting axial thrust, and the strength of the consolidated body should not be less than the strength condition of the consolidated body formed by pisolite and cement slurry.

According to the actual needs, a centering ring can be installed in 3-6 rings. Fig. 11 is a projection view after the hose is installed along the heading direction. 9

Claims (5)

1. A method for centralizing TBM segments is characterized by comprising the LU502525 following steps: (1) Segment the segment installation interval reasonably, 3-6 ring segments are provided with a ring hose, and each ring hose is formed by splicing several small hoses which adapt to segment arc length; (2) On the segment to be installed with hose, install the small hose on the segment from the bottom arch, and the I-beam is arranged in the small hose at the bottom; (3) According to the installation sequence of segments, continue to install small hoses on segments, and with the assembly of segments, fill the hoses into the gap between the excavated section and segments; (4) When the standard segments on both sides are assembled, inject high-strength quick- setting cement slurry into the small hose at the bottom arch, and block the grouting hole after the injection; At the same time, grout is poured into the small hoses on both sides to ensure symmetry as much as possible; (5) Continue to assemble the segments and hoses. After the hoses are completely spliced with the segments, grout into the small hoses at the adjacent block and the capping block. After the grouting is completed, the grouting holes need to be blocked.

2. The method for centralizing the TBM segments according to claim 1 is characterized in that the I-beam in the small hose is longitudinally arranged along the excavation direction.

3. The method for centralizing TBM segments according to claim 1 is characterized in that metal strips are uniformly embedded and welded in the hose, and the metal strips form a certain included angle on the inner wall of the hose.

4. The method for centralizing TBM segments according to claim 1 is characterized in that the middle position of each small hose is provided with a hose connector, and the hose connector is communicated with the grouting hole in the center of the segment.

5. The method for centralizing the TBM segments according to claim 1 is characterized in that the grouting hole in the center of the segment is provided with a pipe embedded part, and the pipe embedded part is connected with the hose connector through threads.