There are a variety of problems encountered in tunnel construction lining trolley. When we encounter problems and then solve them, it will be more troublesome. Therefore, we have sorted out some common problems and solutions of tunnel construction lining trolley. You can learn in advance. Now, if we really encounter these problems during operation, it will be much easier for us to solve them.

 

1. What preparations need to be done before the trolley is installed

When the trolley arrives at the construction site, the following installation work must be prepared:

1. Installation site: depending on the size of the trolley, a stacking and installation site should be set aside, generally 20m x 20m;
2. Sleepers and rails: sleepers are generally 15mm x 15mm x 800mm, and rails are 43kg heavy rails;
3. Lifting equipment: When installing the mast on most trolleys, the existing excavators or loaders on the site can be used for direct installation, but when installing the upper platform and template, a crane of 16 tons or more must be used for installation;
4. There are 6-8 installation assistants, usually by the manufacturer’s after-sales service personnel to install the trolley;
5. Welding machine, gas cutting equipment, handle the connecting parts of the reinforcement parts during the transportation of the trolley;
6. Wooden boards are generally required to be more than 5cm thick and are used for erecting and installing operating platforms.

2. How to determine the center line of the trolley

When positioning the trolley, the center line of the trolley must be determined first. The method to determine the center line is very simple. There is a positioning cross line at the top center position, and the intersection point is the center line point of the trolley that the manufacturer has set before making the trolley. The center line of the trolley can be found by passing this point and drawing the gravity vertical line.

 

3. How to measure the section size of the trolley

When the jacking cylinder is designed below, because the cylinders on both sides prevent the measuring tool from directly measuring, it is not easy to measure the dimensions of the widest point of the trolley. A horizontal line can be drawn on the trolley template, and the height of the two sides can be consistent with tools such as level gauges, and a rod (such as fine rebar, etc.) can be welded, and then the rod can be drawn out through measurement to obtain its cross-sectional width.

 

4. how to locate the trolley

Before the lining work of the trolley, the trolley must be positioned so that the contour section size of the trolley is consistent with the required size. After the trolley travels to the section to be lining, it is positioned through the following actions:

1. Adjust the center line of the trolley by operating the translation cylinder of the hydraulic system to align with the center line of the tunnel;
2. Operate the hydraulic system to lift the cylinder to raise the trolley to the standard lining height, then tighten the foundation jack, and then review the height dimension;
3. Operate the hydraulic system to extend the piston rod of the lateral cylinder and reach the standard lining section, and then manually pull the lateral support screw jack to reach the support position of the lateral cylinder and tighten it;
4. After completing the above actions, the cross-sectional dimensions should be reviewed to prevent errors.

 

5. How to demould the trolley

After a set of trolley lining is completed, it takes 8-24 hours to demold. The demolding action is opposite to the positioning action:

1. Remove the stopper template;
2. Remove the side mold lateral support screw jack (usually remove the jack pin at the end of the template), and retract the lateral cylinder to a certain demolding distance;
3. Shrink the jacking cylinder to lower the trolley to a certain position, and the demoulding is completed.

 

    6.what kind of release agent is used for general trolleys

In order to make the lining of the trolley better demould, and to make the lining concrete surface smooth and smooth, generally need to use a release agent, the choice of the release agent may vary according to the specific situation of the user, generally there are The following methods are as follows: professional mold release agent, machine oil, vegetable oil, template paint, and the template paint can be brushed once after lining three to five molds.

 

7. How to solve the problem that the curvature does not match locally when the front and rear molds of the trolley are overlapped

The trolley template will have local small welding deformation and plastic deformation during welding, transportation, etc. The after-sales service personnel will make appropriate adjustments according to the needs during installation, so that the contour error of the installed trolley is controlled within 3mm , The staggered platform and staggered stitching between templates are controlled within 1mm. When lining the first two groups, due to the hole position error between the front and the last template, to a certain extent, it will cause the template to produce a small linear error locally, causing the phenomenon of local arc mismatch when the front and rear templates are overlapped. This phenomenon is normal and does not affect the normal use of the trolley. When the second mold is positioned after the first set of lining is completed, the manufacturer’s on-site after-sales service personnel will take appropriate treatments for the local arcs that do not match (strong support and Cooperate with the thermal calibration in place), make it fit the first mold radian, and reach the acceptance standard of the lining. After lining the three sets, this problem no longer exists. Under normal circumstances, when the trolley is positioned, it can be fitted into place by itself only by relying on the support rod system of the trolley itself, and the manufacturing and deformation errors are quite small.

 

8. How to overlap the starting point of the trolley lining with the low side wall

How the trolley overlaps the low side wall is related to the specific construction technology of the construction unit. Generally speaking, the user needs to pour the low side wall first. The specific construction process will be clarified when the trolley technology is disclosed. Therefore, the corresponding mark will be marked on the trolley assembly drawing. When pouring the low side wall, the user can refer to the trolley The final assembly drawing shall be constructed in place according to the size and position shown in the figure. When lining, the trolley travels to the lining position and is positioned. The starting point of the side mold of the trolley will be in close contact with the pre-designed overlap line (surface). In order to prevent changes in the small-scale construction process, the trolley is generally designed with a 5cm overlap for adjustment. In some engineering constructions, the low side wall is poured together with the trolley for lining, and the lap positioning is similar.

 

    9.why sometimes there will be mold running and misalignment in the process of trolley lining

In the process of pouring the lining of the trolley, sometimes the phenomenon of running mold and dislocation occurs, mainly in the following aspects:

1. The pouring speed is too fast, or the concrete drop on both sides of the trolley is too large, which will cause a certain impact on the trolley itself;
2. When the trolley is positioned, part of the screw jacks are not fully supported in place and tightened, and they are recovered when they are squeezed by external force, resulting in a die gap and a misalignment;
3. The door frame structure design of the trolley is defective, and the force transmitted by the side mold to the door frame column is too large, which causes the door frame column to retract, and even obvious deformation in severe cases;
4. The existing local arc mismatch has not been dealt with properly, and the normal installation and after-sales service treatment is lacking.

 

10. What are the reasons for the uneven surface of the lining concrete?

There are two main reasons for the uneven surface of the lining concrete, such as rough and uneven surface, pores, and poor gloss. One is that the air bubbles generated near the formwork during the lining process are not completely discharged, and some are attached to the concrete surface of the formwork. The concrete causes pores; the second is that the concrete is too dry, and it is not evenly smashed in place when shaken, causing defects. In order to solve this problem, consider using thinner concrete when lining the bottom side wall, and use vibrators, vibrating rods and other tools for proper and necessary vibrating. If using a vibrator, try to control the vibrating time within 8 seconds to prevent damage to the trolley.

 

11. Why does the gap between the templates and the amount of misalignment become larger

In the existing design, the connection between the templates is connected by bolts, and there is a 1mm gap between the hole diameter and the bolt diameter. When the trolley is used for a period of time, due to the use of vibrators, vibrating rods, etc., the gap will be shifted, and then a certain template gap and misalignment will be generated. Therefore, it is recommended that after every 5 molds of the trolley, the connecting bolts between the molds should be re-fastened manually, and the local problems that have appeared gaps or misalignments should be dealt with. If it is a long tunnel, consider welding the joints between the formwork after the trolley is installed and debugged, which can also effectively prevent the occurrence of gaps and misalignments between the formwork.

 

12. How to control the relative displacement between the trolley mast and the formwork when the construction is steep

In the construction of highway engineering tunnels and hydraulic engineering tunnels, there are usually certain horizontal and vertical slopes, especially the longitudinal slope has a greater impact on the trolley. Due to the large gradient height difference between front and rear, and the momentary impact force when the trolley starts, there is a tendency of relative movement between the two major components of the trolley mast and the template, and it will tilt in severe cases. In order to prevent this phenomenon, two sets of anti-deflection devices or “eight” weights should be added between the door frame and the template (including the upper frame) to restrict each other, reduce mismovement to a certain extent, and protect the use of the trolley. Security.

 

13. How to maintain and maintain the trolley

1.Replace the hydraulic oil after the trolley works for 15 working days.

2.Grease the screw jacks in each working cycle to remove the concrete on the surface of the portal frame, jacks and formwork.

3.Mold release agent must be applied to the template during each working cycle.

4.When pouring concrete, the piston rod of each cylinder must be covered to prevent the concrete from falling on the surface of the piston rod.

5.After each demolding, check whether the connecting bolts are loose. If they are loose, they must be tightened. The connecting bolts of the five molds must be fully tightened to prevent gaps and misalignments between the trolley templates.

 

 

14. How to deal with if there is no pressure in the hydraulic system of the trolley

When the full hydraulic lining trolley is installed, debugged or used, if the hydraulic system feels no pressure, it may be caused by the following reasons in general:

1. Reversal of the hydraulic motor: it can be solved after the two wires of the external power supply are swapped;
2. Valve group failure: The most likely cause is that the valve core is blocked. The valve group can be disassembled and cleaned carefully;
3. Quality problems or power failures of hydraulic motors can be solved by replacing parts.
4. If the hydraulic oil and pipeline are contaminated, the pipeline should be cleaned and the hydraulic oil should be replaced.

 

15. What is the problem with the abnormal situation of the hydraulic cylinder?

Because the trolley is used in a relatively harsh working environment (especially when a large amount of concrete or dust is left on the rods), and the hydraulic cylinders are frequently operated, the cylinder body and rods are under great pressure, causing some hydraulic cylinders to appear Abnormal conditions such as no pressure, oil leakage, slow expansion, etc., have greatly affected the operation progress of the second lining construction of the project. The occurrence of this phenomenon generally means that the seal of the hydraulic oil cylinder has been damaged, causing the oil cylinder to leak in or out of the pipeline during operation, which reduces the work efficiency or even fails to work normally. For this reason, it is recommended to disassemble the oil cylinder and replace the good seal.

 

The above is a detailed explanation of the common problems and solutions of the tunnel construction lining trolley. I hope to help everyone. Gaofei Machinery is a company that integrates the research and development, production, sales, installation and maintenance of bridges, tunnels and mechanical equipment.

In recent years, lining trolleys have been used more and more widely in the construction of railways and highways. The relevant Ministry of Construction has also paid more and more attention to the quality of tunnel lining, and required the design, production and use of lining trolleys. Also getting higher and higher. However, due to the relatively weak ability of some construction workers to deal with the related performance and common problems of the trolley, the quality of the lining failed to achieve the expected effect. We now summarize some common problems and treatment methods about lining trolleys as follows, hoping to give you some reference.

Common problems of lining trolley

1. What are the preparations for the installation of the lining trolley?
The tunnel lining trolley must be prepared for the following installation work when it arrives at the construction site: installation site, sleepers and rails, lifting equipment, 6-8 installation assistants, welding machines, gas cutting equipment, wood planks, generally requiring a thickness of more than 5cm.
2. How to determine the center line of the trolley
When positioning the trolley, you must first determine the center line of the trolley. The method to determine the center line is very simple. There is a positioning cross line at the top center position. The intersection is the center line point of the trolley that the manufacturer has set before making the trolley. And draw the gravity vertical line, you can find the center line of the trolley.
3. How to locate
Before the tunnel lining trolley performs lining work, the tunnel lining trolley must be positioned so that the profile section size of the tunnel lining trolley is consistent with the required size.
4, the overall deformation of the platform
After the lining trolley is impacted, it has different degrees of deformation, which is invisible to the naked eye. It will affect the forming effect after the infusion is stressed. This small degree of deformation will gradually increase the degree of deformation after multiple infusion operations. It will seriously affect the overall deformation of the platform, so the trolley mast must be hung with obvious slow-moving and no-go signs.
5. The sinking problem of rail sleepers
The sleepers must have steel plate support pads, and the sleepers used on the rails must not have rotten sleepers, especially under the wheel sets.
6. Which release agent is used for the lining trolley?
In order to make the tunnel lining trolley better demould and make the concrete surface smooth and smooth, it is generally necessary to use a release agent. The choice of the release agent depends on the specific situation of the user. Generally, there are the following types Method: professional mold release agent, machine oil, vegetable oil, template paint, the template paint can be brushed once after three to five molds.
7. How to measure the section size of the lining trolley
When the jacking cylinder is designed below, because the cylinders on both sides hinder the direct measurement of the measuring tool, it is not easy to measure the wide point and other dimensions of the tunnel lining trolley. A horizontal line can be drawn on the template of the tunnel lining trolley, and the height of both sides can be the same through tools such as a level, and a rod (such as fine rebar, etc.) can be welded, and then the rod can be drawn out by measuring to obtain its cross-sectional width size.
The above is the analysis of the common problems of the lining trolley. As long as you carefully observe and compare the analysis, find the reasons, continue to summarize, strengthen the training of construction personnel, fix the first-line construction personnel, strictly operate the rules, strengthen the concrete construction process and other aspects to take effective improvements. The measures can completely make the lining quality meet the standard requirements and reach a satisfactory level.

Broadly speaking, the artificial support structure can be collectively referred to as lining, which can be divided into primary support and secondary support (secondary lining). Tunnel lining materials should first have sufficient strength, durability, impermeability, corrosion resistance and frost resistance. In addition, from an economic point of view, it should also meet the requirements of obtaining local materials, reducing the cost, convenient construction and easy mechanized construction.

Concrete

Advantages: Good integrity, can be poured on site, can also be prefabricated in the processing field, and can be mechanized construction. Additives can be added to the cement to improve the performance of the concrete.

Disadvantages: Can not bear the load immediately after pouring, it needs to be kept in good health, and the mold can be demolished after reaching the predetermined strength, and it takes up more templates and arches. Ordinary concrete has poor corrosion resistance.

Stone concrete

(1) For railway tunnels, in order to save cement, schist concrete is allowed to be used for the lining of side walls in good rock sections (the content of schist should not exceed 20% of the total volume). In addition, when there is over-excavation at a site other than 1m above the arch line, the over-excavated part can also be backfilled with rubble concrete.

(2) The selected stone should be hard, its strength grade should not be lower than MU40, and the stone with cracks and easy to weather should not be used to ensure the quality.

(3) The lining of highway tunnels is generally not used, and rubble concrete can be used for the inverted or over-excavated part. The dosage of rubble shall not exceed 30% of the total volume.

RC

It is mainly used in open excavation sections such as tunnel doors and open tunnel linings, or when the tunnel passes through seismic areas, biased pressure, through fault fracture zones or silt, quicksand and other bad geological sections.

Precast stone and concrete blocks

Advantages: it can obtain materials on site, reduce the cost, ensure the thickness of the lining and bear the load earlier, save cement and formwork, and have better durability and corrosion resistance.

Disadvantages: poor integrity, many joints are prone to water leakage, poor waterproof performance, construction is mainly manual operation, difficult to mechanize construction, labor and time, slow construction progress, and high masonry technical requirements. Retaining walls of cave doors, retaining walls, and curbs of exposed lines can still be used. The strength grade of block stones should not be lower than MU60, and the strength grade of blocks should not be lower than MU20. Stones with cracks and easy weathering should not be used.

Shotcrete

Shotcrete is made by spraying concrete dry mix, accelerator and water onto the clean rock surface at high speed with concrete sprayer.

It has high compactness and can quickly close the fissures of surrounding rock. It is closely attached to the rock surface and has high early strength. It can quickly seal the rock surface and support it. In addition, fiber materials can be added to the shotcrete to improve its performance. It is an ideal lining material.

In ordinary railway tunnels, shotcrete can be used as the middle inner lining, but its strength grade is not lower than C20, the cement grade used is not lower than 32.5, and ordinary Portland cement is preferred. The fine aggregate is made of hard and durable medium sand or coarse sand, the fineness modulus should be greater than 15, and the moisture content of the sand should be controlled within 5%-7%; the coarse aggregate should be made of hard and durable pebbles or gravel, and the particle size should not be larger than 15mm.

Anchor rod and steel frame

Anchor rod is a rod-shaped member inserted into the surrounding rock mass to reinforce the surrounding rock. It can be divided into mechanical anchors, bonded anchors and prestressed anchors. The diameter of the anchor rod should be 20～32mm, the material of the rod should be HRB335, HRB400 steel; the material of the backing plate should be HPB235 steel. The strength of various cement mortars used for bolts should not be lower than M20. The reinforcement mesh material can be HPB235 steel with a diameter of 6-12mm.

The steel frame is a section steel support or grid steel support placed in the primary support or secondary lining in order to strengthen the support rigidity.

The steel frame used for the initial support should be made of H-shaped, I-shaped, U-shaped steel, or steel pipe or rail.

Fabricated materials

In shield construction, fabricated materials are often used as lining materials, such as large prefabricated blocks of reinforced concrete and cast iron prefabricated blocks with reinforced ribs.

In the construction of shed-type open caves (referred to as shed-holes), prefabricated slabs or beams can be used to assemble plate-type sheds or beam-type sheds.

When using the new Austrian method of construction, in order to waterproof, anti-falling and beautiful requirements, you can also add an off-wall structure. Commonly used materials are corrugated steel arched large assembly preforms, and sometimes glass fiber reinforced plastic can be used instead of steel.

Various decoration materials can be pasted on the inner surface of the lining in order to improve the lighting, waterproof, ventilation, aesthetics, sight induction or reduce noise in the cave.

Tunnel construction is a difficult point in road and bridge construction. It has a complicated construction process and is different from other projects. It has the characteristics of concealment. If the survey and design estimates are insufficient or some precautions are not done during the construction, the safety of the tunnel may be affected and the project cannot be carried out normally. Therefore, when carrying out tunnel construction, it is necessary to understand the key points of the construction, strictly control the quality of each key point, strengthen management, and ensure safety.

Jet machine

1. The spraying equipment should have good sealing performance, and the conveying material should be continuous and uniform to meet the requirements of spraying operations.

2. Determine the reasonable water-binder ratio, water consumption, cementing material consumption and sand rate to ensure workability and early strength.

3. Sequential spraying from bottom to top in segments, the length of the segment is not more than 6m; the thickness of the arch should not exceed 6cm at a time, and the side wall should not exceed 10 cm. When spraying in layers, the next layer should be sprayed on the previous layer. The concrete should be set after the final setting. If spraying is carried out after 1h of final setting, the surface of the spray layer should be cleaned with high-pressure air and water first. The nozzle should be perpendicular to the rock surface and the distance from the sprayed surface should be 0.8~1.2m.

4. The spray pressure should be controlled at 0.15~0.2Mpa, and the concrete should be wet cured after spraying for 2h after final setting, and the curing time should not be less than 14d.

5. The spraying workers should wear protective equipment such as dust masks, protective caps, protective glasses, dust masks, etc. The workers should avoid direct contact with alkaline liquid quick-setting agents. After accidental contact, they should immediately rinse with water and spray concrete. After completion, the equipment should be cleaned in time.

6. The surface of the shotcrete should be flat, without hollows, cracks, or looseness. The base surface should be leveled with shotcrete. The flatness should be checked with a 2 m ruler. The allowable deviation of the surface flatness is 5 cm for side walls and 7 cm for arches.

Common problems on site

1. There are cavities and not dense behind the vault and side walls of the tunnel.

2. The thickness of the sprayed concrete is insufficient, uneven, and the steel frame is not completely covered.

3. Use dry spray. All tunnels that do not use wet spraying are required to stop construction.

4. The spraying distance is too far, and the sprayed surface is above 1.2 meters, which cannot guarantee the compactness of the concrete.

5. The spraying sequence is wrong, not bottom-up, but rather random.

6. The thickness of one shot is too thick, causing the concrete to hollow, not compact and collapse.

Anchor rod

Anchor rod is a rod body made of solid or hollow steel in the rock mass in order to avoid the loose collapse of the rock mass during the excavation of the surrounding rock, which plays the role of reinforcing the soil and connecting it into a whole. The rock space is consolidated with mortar or other materials and fixed with steel pads.

Construction points

1. The anchor rod construction should be carried out after the initial spraying of concrete. The anchor rod shall be drilled in by special machinery. When using a general pneumatic rock drill, a special impactor shall be equipped. The main structural plane is vertical.

2. Arrange the position according to the design requirements, the allowable deviation of the hole position is not more than 10cm, and the insertion length of the rod shall not be shorter than 95% of the design length.

3. When the rod body is inserted into the anchor rod hole, the position should be kept centered and the insertion depth should meet the design requirements.

4. The mortar pouring into the mortar bolt hole should be full and dense, and an appropriate amount of micro-expansion agent and accelerator can be added into the mortar or cement slurry.

5. After the anchor rod is installed and the filled mortar is finally set, the supporting plate should be installed immediately and the nut should be tightened.

Common problems on site

1. The number and length of bolts are lower than the design value, and the distance between bolts is large. The lock foot anchor rod and the steel frame are not U-shaped welding. The on-site inspection should separate the leading small pipe, leading anchor rod, hollow anchor rod, and locking foot anchor tube (rod) in detail.

2. The raw material of the anchor rod is not up to the standard, and the wall thickness of the anchor rod and weighing inspection shall be checked on site.

3. The hollow bolt designed for grouting is not grouted or replaced by mortar bolts.

4. The penetration angle of the anchor rod does not meet the design requirements.

Steel frame

The steel frame is a support skeleton structure made of steel gratings, section steel, steel rails, etc., which are laid out according to the tunnel excavation contour line in order to keep the surrounding rock stable during the initial support period of the tunnel excavation in the tunnel escape pipeline project. After installation, it can achieve the purpose of supporting the stability of the surrounding rock and limiting the deformation of the surrounding rock. It is usually combined with steel mesh and shotcrete to bear the force.

Construction points

1. The steel frame shall be erected in time after the initial spraying of concrete.

2. The steel frame should not be sectioned on the vault with greater force and other places with greater force. The diameter of the main reinforcement of the grid steel frame should not be less than 18mm, and the welding between the steel bars should be firm.

3. Each section of the steel frame should be connected by bolts, and the connecting plates should be closely attached, and the gap should not exceed 2mm.

4. The outer edge of the steel frame should be tightly wedged with steel wedges or precast concrete blocks. The steel frame should be covered by sprayed concrete. The thickness of the protective layer should not be less than 40mm. The gap between the steel frame and the surrounding rock must be filled with sprayed concrete.

5. After the steel frame is processed, a trial assembly check must be carried out. The allowable error of the peripheral assembly is plus or minus 3 cm, and the plane warpage should be less than 2 cm; the erection position is accurate, and the deviation of the steel frame spacing, lateral position and elevation from the design position does not exceed Plus or minus 5 cm, the verticality error is plus or minus 2°; in the case of the partial excavation method, the steel arch frame is positioned by locking foot anchor pipes (rods) after installation, and the number is two. After the lower half of the excavation, the steel frame should be extended in time to form a closed loop; the two rows of steel frames shall be firmly connected longitudinally with a 22-diameter steel rod with a circumferential spacing of 1m to form an overall stressed structure.

6. When the steel frame is installed, the inner contour size should be strictly controlled, and the amount of settlement and deformation should be reserved to prevent intrusion into the lining clearance.

The rescue process of tunnel collapse is very complicated, and the rescue time is relatively long. The rescue situation usually takes 3 to 6 days. Therefore, it is very necessary to quickly open the “life channel” to transport air and food to the trapped persons, and to carry out information transmission and psychological intervention. ; The tunnel escape pipeline can reconfirm the length of the collapsed body and guide the construction of the escape channel.

In recent years, due to the acceleration of the internationalization process, the transportation industry has developed rapidly. Road construction is not only related to people’s livelihood, but also an important pillar to promote national economic growth. In order to promote regional economic development, many regions have overcome geographical restrictions to build highways, and tunnel engineering is an important construction link. Tunnel projects are often located in areas with very complex geographic environments, including geological conditions and topography, etc., which require tunnel engineering construction technology. As a large-scale project, tunnel engineering not only has many and complex construction techniques, but also has high requirements for professional technology. In particular, there are many influencing factors in the tunnel engineering environment, which will inevitably cause various quality problems in tunnel construction. In order to ensure the construction quality, it is very necessary to formulate supervision measures according to the actual needs of the tunnel project.

Features of tunnel construction

Concealment

Tunnel engineering is a concealed project, and the construction of tunnel engineering must also have the characteristics of concealment. During construction, there is often only one visible side, and other constructions are concealed, which will inevitably have many unforeseen conditions. Even if there are hidden dangers left during construction, it is difficult to find out in time and make judgments.

Dynamic

The environment where the tunnel project is located is often complex and changeable. During the construction, this change will inevitably produce various accidental factors, which will cause the construction design to be inconsistent with the construction site. This means that to design a tunnel project, it is necessary not only to conduct site surveys, but also to fully understand the local surrounding rock conditions, so that the tunnel lining trolley is dynamic, so that the initial design is convenient when the construction site conditions change. to modify.

Risk

The area where tunnel construction is located is often in harsh environmental conditions, and most of the construction is carried out in caves or underground. Even if the operation is carried out in the same environmental space, the technical requirements of each operation link will be different, including tunnel lining technology, support technology and ventilation technology, etc., which must be selected according to the actual needs of the construction to ensure that each construction The links are closely connected, which will inevitably make the construction environment cramped, and different construction technologies will interfere with each other, which will inevitably have risk factors. In particular, the geological conditions of the tunnel construction area are changeable, and the lack of stability will inevitably have risks, making the tunnel construction dangerous accidents at any time.

Influencing factors existing in tunnel construction

Human Factors

In tunnel construction, people are the most active factor and also the factor lacking stability. To effectively control the tunnel construction, it is necessary to analyze in detail the potential safety hazards in each link of the construction, and formulate targeted control measures to play a management role in the construction. The staff involved in the construction activities should control the basic work in the construction, and analyze various intervention forms based on this. As the constructors in the construction proceed from their personal interests and ignore the responsibilities they should perform in the work, there will be problems in the adjustment of construction management procedures, which will inevitably affect the quality of tunnel construction.

Hard factor

The rigid factors that affect tunnel construction include material factors and equipment factors throughout the entire tunnel construction process. An important measure of the quality of tunnel construction is the material. To ensure that construction materials comply with relevant regulations, it is necessary to consider various factors that affect material quality. These factors are often important influencing factors leading to material problems, as well as basic factors affecting the quality of tunnel engineering. In tunnel construction, construction equipment is indispensable and the main object of construction safety management. To control and manage construction equipment, it is necessary for construction personnel to pay attention to equipment inspection. However, because the construction personnel neglect the daily maintenance of the equipment, it will inevitably have a negative impact on the construction of the tunnel project.

Technical control measures

During tunnel construction, scientific and reasonable technical control measures are the key to ensuring construction quality. However, when entering specific operations, it will be affected by a variety of factors, making it difficult for technical control measures to function. This is usually reflected in changes in construction procedures or adjustments to construction procedures, which will inevitably cause adverse effects on subsequent construction . To do a good job of technical control in tunnel construction, it is necessary to analyze various influencing factors and propose scientific and effective intervention measures to make technical control time-effective.

Key points of supervision and control of tunnel construction

Supervision and control of excavation site

Tunnel construction will have problems with over-excavation and under-excavation at the excavation site. Supervisors should conduct excavation quality inspections in accordance with the content specified in the relevant technical specifications. For under-excavation, if the rock formation is complete, the strength and structure of the lining will not be disturbed. When the compressive strength of the rock exceeds 30 MPa, the under-excavation amplitude in individual places should be defined within 0.1 square meters, and the uplift should not exceed 5 meters. . Including the position of the vault of the tunnel less than 1 meter and the corners of the walls must not be under-excavated to avoid dangerous accidents. The over-excavation phenomenon has been clearly stipulated in the tunnel engineering construction technical specifications. Due to the different geological rings of the surrounding rock, there will be different requirements for over-excavation.

Supervision and Control of Anchor Shotcrete Support

In tunnel construction, the bolting and shotcrete support cannot be ignored. In the process of acceptance of the tunnel project, the supervisor shall formulate the acceptance method according to the actual situation of the tunnel construction and notify the construction party in advance. Acceptance is required for every construction link in tunnel construction, and follow-up work can only be carried out after the acceptance is qualified. In the acceptance of the construction quality of anchor rods, attention should be paid to checking the angled anchor rods. In the acceptance of grouting construction, the supervisor must attach great importance to this process, because this process is not only technically difficult, but also has strict requirements on the grouting procedure.

Supervision and control of shotcrete

If there are omissions in the process of spraying concrete during tunnel construction, not only cracks will occur, but even water seepage will occur, which will cause adverse effects on the construction. The supervisor shall strictly control the sprayed concrete construction and require the construction personnel to adopt advanced technical measures to ensure the quality of the tunnel project.

Supervision and control of invert

In tunnel construction, the invert is an important construction part, which is related to the stability of the entire tunnel. If there are quality problems in the invert construction, it will affect the stability of the superstructure, especially the junction between the wall corner and the invert. It needs to be cleaned up before entering the construction process to avoid impurity in this part. The arch is not strong and produces uneven settlement.

In summary, there are high requirements for construction technology in tunnel construction, mainly because tunnel construction is a hidden project, and it is difficult to find hidden quality problems. This requires the analysis of the possible influencing factors in the tunnel construction, the exploration of technical methods, and the adoption of supervision and control measures that conform to the actual construction to avoid quality problems during the construction and ensure the smooth construction of the tunnel construction.