The characteristics of modern tunnel construction and development are closely related to scientific and technological progress, social and economic development and sustainable development concepts:

a. The progress of human science and technology, especially the rapid development of computer technology and information technology, enables the force of the tunnel excavation process to be accurately controlled through numerical simulation and monitoring and measurement information feedback, and realizes the “dynamic design and construction”;

b. The mechanical equipment for tunneling is constantly improved and intelligent, which can protect the integrity of the surrounding rock and the safety of the construction process to the maximum extent;

c. The concepts of energy saving, emission reduction, ecological protection and sustainable development are gaining more and more popularity;

d. The people-oriented construction concept is continuously deepened.

According to the above concept, combined with the characteristics of modern tunnel construction and operation, it can be summarized into the following aspects:

1) The tunnel is repaired longer

With the improvement of road grade standards and the continuous improvement of tunnel design theory and construction technology, the construction length of highway tunnels has grown from 2 ~ 3km in the 19th century to tens of kilometers now. In the 20th century, the Guanyue tunnel in Japan was 11.06km long, the Mont Blanc tunnel in Italy was 11.6km, the Orland tunnel in Norway was 24.5km, and the Xinguanjiao tunnel in China was 32.6 in this century. km, the new Gotthard tunnel in Switzerland is 57.0km long. In addition, Qinling Zhongnanshan Tunnel, the longest road tunnel in China with a total length of 18.02km, has been constructed. The successful construction of these long highway tunnels, in addition to the increased requirements of highway grade standards, new construction techniques, modern ventilation monitoring technology, and many successful experiences play a decisive role.

2) More and more curved tunnels

Driven by the new tunnel design theory and construction technology, especially after summarizing the practical experience of highway tunnel operation and management, the route selection of modern kilometers of tunnels has completely broken the previous rules of straightness and no bending. Curved tunnels are gradually increasing. It is more common in foreign countries. For example, the Balassky double-track tunnel in Austria has designed a curved tunnel with a length of 1.2km in combination with the terrain and environmental conditions. The main reasons for the increasing number of curved tunnels are:

a. Avoid bad geological areas and improve the safety of the tunnel structure;

b. Limit the driving speed to fully ensure driving safety;

c. It can effectively control the glare caused by accelerating out of the hole, which is very helpful to avoid traffic accidents.

3) The tunnel span is getting bigger and bigger

From the perspective of geotechnical mechanics, the span of the tunnel is an important indicator that can be used to measure the stability of the tunnel project and the difficulty of construction. Generally speaking, the larger the span, the more unfavorable the stability of the surrounding rock of the cave. In addition, the larger the span, the greater the impact of adverse geological conditions (such as faults, etc.), which will cause difficulties in tunnel construction. Therefore, the construction and operation of large-span tunnel underground engineering marks the new progress and maturity of investigation, design and construction technology.

4) Longitudinal ventilation is dominant

In the 20th century, most of the nearly 400 highway tunnels with a length of more than 3km built abroad were fully horizontal or semi-horizontal ventilation, represented by Switzerland, Austria and Italy.

In recent years, with the practice of longitudinal ventilation in long highway tunnels, the ventilation methods of highway tunnels are basically divided into two groups: horizontal ventilation or semi-horizontal ventilation represented by Europe and vertical represented by Asia and Japan Type ventilation. With the increase of vehicle emission limit standards, the factors that control the ventilation volume of highway tunnels have gradually transitioned from CO to smoke concentration, and the double-hole scheme has gradually replaced the single-hole scheme. Therefore, segmented vertical ventilation has become dominant. Japan believes that the sectioned longitudinal ventilation method with electrostatic precipitator can be adapted to any traffic and highway tunnel of any length. European countries have also gradually changed their traditional ideas. In many newly built or extended double-track long road tunnels, the horizontal ventilation method in the past has been used to replace the horizontal ventilation method in the past. Several long and large highway tunnels constructed in China basically adopt longitudinal ventilation or section longitudinal ventilation.

5) Double holes replace single holes

Single-hole two-way traffic cannot fully utilize vehicle traffic wind, and requires increased installed capacity of ventilation equipment, especially the accident rate of single-hole two-way traffic is much higher than that of double-hole one-way traffic. Cave two-way traffic tunnel. According to incomplete statistics, foreign countries are changing more than 100 single-hole two-way traffic tunnels built in the early days into double-hole one-way traffic tunnels, which is very helpful for reducing the difficulty of ventilation, saving energy, and reducing traffic accidents.

In addition, the double-hole traffic can greatly increase the traffic volume and meet the requirements of disaster prevention, disaster relief and combat readiness. The Balaski tunnel and the Tauern tunnel in Austria are typical examples.

The highway tunnels constructed in China are all double-hole one-way traffic tunnels. However, the secondary roads and the road tunnels below the second level are basically single-hole two-way traffic tunnels. With the increase of traffic volume, the single-hole two-way traffic tunnels of some secondary highways have gradually changed to double-hole one-way traffic tunnels.

6) Diverse tunnel functions

The main function of highway tunnels is for car traffic, that is, traffic function. However, the long road tunnels built by humans, especially the extra-long road tunnels, the tunnels that are difficult to construct and the high-cost tunnels, will arouse the people’s attention and curiosity. Therefore, tourism has become a long road tunnel Another obvious feature, prominent examples are the English Channel Tunnel, Tokyo Bay Tunnel, Hong Kong Bay Tunnel and Shanghai Yanan East Road Tunnel.

7) Underground interchange is becoming a reality

At present, the domestic underground engineering construction is developing rapidly, but its function is partial, and the city should take the road of deep stratum, multi-function and three-dimensional development in the future to truly achieve the sustainable development of the city. In this regard, some cities in Europe and the United States have come to the forefront. Underground expressways have been built in Boston, USA and Tokyo, Japan. Highway interchange interchanges have large spans, complex structures, and difficulty in close-up construction. The operation techniques such as ventilation and disaster prevention are more difficult, which poses challenges to tunnel design theory and construction techniques. At present, China’s highway interchange is also starting. For example, the first large-scale underground underground interchange in China-Xiamen Wanshishan Underground Interchange Tunnel is an underground interchange structure that has both plane bifurcations and upper and lower intersections, and its structural characteristics are manifested. It is the largest span structure section width 25.8m; the double arch section is asymmetrical structure, and the small clear interval section contains 1.42 m rock.

In summary, the tunnel project has become an important part of national construction and people ’s life and production. It is a manifestation of space expansion and resource intensiveness. It is also a collection of geology, geotechnical, structural, computational mechanics, machinery, electromechanical, information control and disasters. Comprehensive technology of prevention and emergency response in multiple disciplines and fields. Although tunnel construction and technology in China have achieved great achievements in recent years, there are still many problems that need to be further studied and resolved. Due to the irreversible and difficult-to-change characteristics of the tunnel, it is difficult to change once it is completed. Therefore, the planning, design, and construction of tunnel construction must be scientific, rational, and high-quality.

The working conditions of the tunnel lining trolley are severe and the load is heavy. The experiment proves that the life of the parts of the walking system is the shortest compared with other parts of the lining trolley. Therefore, the walking system must be used and maintained correctly to improve its traffic performance, reduce the power loss of the moving parts, and extend the service life of the machine parts.

Use correctly

(1) When driving, you should operate correctly in accordance with the driving rules and methods to avoid severe vibration and violent impact.

(2) When driving on soft and gravel ground, avoid making sharp turns at large angles, otherwise, it will cause damage to moving parts.

(3) During training, avoid the lining trolley turning frequently in one direction, so as to avoid the pitch difference between the tracks on both sides (when turning, the wear of high-speed tracks is greater than that of low-speed tracks).

(4) According to the terrain and soil quality of the lining trolley, adjust the tightness of the crawlers reasonably to improve the driving performance of the lining trolley.

Walking system maintenance work content

1. Cleaning, inspection and lubrication

(1) Preparation before leaving the vehicle Each time before leaving the vehicle, a visual inspection of the components in the action section is required. The labyrinth oil retaining device of the side wheel allows a small amount of oil leakage.

(2) First-level maintenance removes dirt from all parts. The lining trolley shall check the following items every time after leaving the vehicle, and eliminate it in time when there is a fault.

A. Use visual inspection to check the tightening of the fastening bolts of each part of the action part where visible.

B. Check the tightness of the track (check every 300 ~ 400km).

C. Check the installation of the fixed card board of the pull arm of the friction damper, and replace it if it is lost.

D. Check whether the axle cover of each wheel and the rewinding oil cover leak or overheat during intermittent driving, and prevent loosening and damage of the bearing in time.

E. When the lining trolley travels to 400km in total, the fasteners of all components should be generally tightened once.

F. Regularly inspect the track shoes and wearing parts, and replace them as appropriate.

(3) The second-level maintenance is carried out after driving for 1400 ~ 1600km. In addition to the first-level maintenance, the following contents need to be completed:

A. Check the rubber tires of the load wheels and induction wheels.

B. If oil leakage is found on the wheels of the load-bearing wheel, the induction wheel and the side wheel, the grease of No. 2 lining trolley should be added. The load wheel and the induction wheel should be added to the upper bolt hole until the lubricating oil flows out; the supporting wheel should be added until the oil mark of the self-tightening oil seal of the supporting wheel facing the car body appears.

C. Check the tightening of the nuts of the induction wheel and the load wheel, and the tightening of the bolts of the balance elbow and friction damper.

D. Tighten the fixing screw of the driving wheel.

(4) The third-level maintenance is carried out after driving for 2800 ~ 3200km. Its purpose is to check the technical status of the lining trolley and make full preparations for continued use. In addition to completing the first and second level maintenance, the following content should be added:

A. Visual inspection of load wheels, side wheels, induction wheels and track adjusters, rubber tires, wheel discs, and wrap-around oil retaining rings. If you want to remove the wheel hub of the load-bearing wheel and replace defective parts, you should remove the old grease and clean all parts with diesel. The bearing should be coated with grease during assembly. After the assembly of the load-bearing wheel is completed, open the two bolts coated with red magnetic paint on the end surface of the shaft cover to fill the oil.

B. Check whether the wear amount of the driving ring gear meets the replacement condition.

C. Replenish the balance elbow shaft with grease. Fill 100 to 200g of grease in the oil injection hole at the lower part of the balance elbow bracket (use oil with the load wheel). Add grease to the load wheel, the induction wheel and the side wheel.

D. Check all parts of the crawler for damage, and replace them if they meet the replacement conditions.

2. Inspection and adjustment of crawler tightness

(1) Checking the degree of tightness of the crawlers The inspection and adjustment of the degree of tightness of the crawlers should be carried out on a relatively flat ground. The methods are as follows:

A. Put the track measuring line on the track ribs of the second and third side rollers, pass the line through the track shoe gap, and hang a heavy object.

B. Use a steel ruler to measure the distance from the measuring line to the track ribs (that is, the middle piece between the second and third side rollers). The maximum value of this distance is the overhang of the track. The amount of drape should generally be in the range of 20 ~ 25mm.

(2) Adjustment of track tightness In order to reduce the power loss when the track is rolling, to prevent the track shoe from jumping or climbing on the driving gear teeth, and to prevent the track from falling off during the driving of the vehicle, the track must be adjusted to an appropriate degree of tightness.

When adjusting the track, make sure that the two tracks have the same tightness. The general drape is 20-25mm, but it should be slightly tighter when driving in mountainous or pebble ground to reduce the rolling resistance of the load wheel; in mud, sand and snow, it should be slightly looser to increase the adhesion.

A. Adjustment of track tensioning mechanism.

a. Raise and fix the front fender, and clean the mud at and around the four sides of the worm tail and the six sides of the screw tail.

b. Loosen the screw: Use the special socket wrench and pry bar in the tool to turn the hexagonal head of the screw counterclockwise or clockwise for 1 ~ 1.5 turns to disengage the worm.

c. Adjustment: put the double head of the socket wrench on the tail of the screw and the worm, so that the worm and the screw rotate together. When the pointer on the cheek of the crank is adjusted within 180 ° under the gap of the sleeve, clockwise Turn the socket wrench to induce the wheel to move forward, thereby tightening the track; press the counterclockwise direction to loosen the track. When the cheek of the crank arm is above the gap of the bushing, clockwise rotation will loosen the track; counterclockwise rotation will tighten the track. This position is generally not used.

d. Lock the worm: After the crawler is adjusted, the worm should be locked to prevent it from loosening. The locking is divided into upper locking and lower locking. If the crank arm is facing upward (the pointer on the cheek is above the gap of the bushing), the upper locking is used, and at this time, tighten the screw counterclockwise. If the crank arm is facing down (the pointer on the cheek is below the gap of the sleeve), the lower locking is used. At this time, tighten the screw clockwise, and the locking torque of the screw is 800 ~ 1000N • m.

e. Check the tightness of the track again. After passing the inspection, drive the car forward for a distance of not less than half the length of the car body, and recheck the tightness of the track. If it does not meet the requirements, it should continue to be adjusted to the specified range.

B. Adjust by replacing or reducing track shoes.

When the track adjuster is adjusted to the limit position and the track cannot be tensioned, one track shoe should be removed from each track and then adjusted to the standard tightness.

When the lining trolley deviates due to different lengths of the left and right tracks, part of the track shoes in the two tracks can be interchanged to ensure that the two have the same length.

For the removed or exchanged track shoes, the inclined section between the driving wheel and the sixth load-bearing wheel should be selected. When removing, the upper supporting track must be tightened to loosen the track under the driving wheel. Before tightening the upper support track, a spare track shoe should be placed under any load wheel (except the sixth load wheel) to prevent the lining trolley from sliding.

Before the tunnel lining trolley starts lining construction, the tunnel lining trolley must be positioned so that the section size of the tunnel lining trolley is consistent with the required size, and the following common problems should be noted during the construction process.

1. What preparations should 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. The sleeper is 15mm x 15mm x 800mm, and the steel rail is 43kg heavy rail;

(3) Lifting equipment. Most of the trolleys can be directly installed by using the existing excavator or loader on the construction site, but when installing the upper platform and formwork, they must be installed with a crane of 16 tons or more;

(4) 6-8 auxiliary installation personnel, usually the after-sales personnel of the manufacturer carry out the trolley installation;

(6) Wooden boards, generally required to be more than 125px thick, are used for erecting and installing operation platforms.

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 of determining the center line is very simple. There is a positioning cross at the center of the top, and its intersection point is the center line point of the trolley that the manufacturer has already made when making the trolley. .

3. How to measure the cross-sectional dimensions of the trolley when the jacking cylinder is designed below?

When the jacking cylinder is designed below, the cylinders on both sides hinder the direct measurement of the measuring tool, so it is not easy to measure the width of the trolley and other dimensions. The horizontal line can be drawn on the trolley template, and the position of both sides can be made high by tools such as a spirit level, and the rods (such as thin screw steel, etc.) can be welded, and then the rods can be drawn to measure the width of the cross section.

4. How to position the trolley?

Before the lining work of the trolley, the trolley must be positioned so that the outline size of the trolley is the same as the required size. After the trolley walks to the lining section, it will be positioned by the following actions:

(1) Adjust the trolley centerline by operating the translation cylinder of the hydraulic system to align it with the tunnel centerline;

(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 check the height dimension;

(3) Operate the hydraulic system to extend the piston rod of the lateral cylinder to reach the standard lining section, and then manually pull the lateral support screw to make it reach the lateral cylinder support position and tighten;

(4) After completing the above actions, the cross-sectional size should be reviewed to prevent errors.

5. How to demold the trolley?

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

(1) Remove the block template;

(2) Remove the lateral support screw jack of the side mold (generally it is enough to remove the jack pin at the end of the template), and retract the lateral oil cylinder to a fixed stripping distance;

(3) After shrinking the jacking cylinder to lower the trolley to a fixed position, demolding is completed.

6. What kind of release agent does the general trolley use?

In order to make the demoulding of the trolley after lining better, and make the surface of the lined concrete smooth and smooth, generally need to use a mold release agent, the choice of mold release agent can vary according to the specific situation of the user, generally The following methods: industrial mold release agent, engine oil, vegetable oil, template paint, which can be painted after lining three to five molds.

7. How to solve the situation that the arc does not match when the front and rear molds of the trolley are overlapped?

The trolley template will undergo local small welding deformation and plastic deformation during welding, transportation, etc. 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 , Staggering and staggering between templates are controlled within 1mm. In the first two groups of lining, due to the hole position error between the front and rear formwork, to a certain extent, it will cause a small linear error locally in the formwork, resulting in the phenomenon that the local curvature does not match when the front and rear formwork overlap.

This phenomenon is normal and does not affect the normal use of the trolley. When the two dies are positioned after the lining is completed, the on-site after-sales service personnel of the manufacturer will properly handle the areas where the local arc does not match (strong support and thermal calibration in place) ) To make it fit with the radian of the mold to meet the lining acceptance standard. After lining the three groups, this problem no longer exists. Under normal circumstances, when positioning the trolley, it can be fitted into place by itself only by the support bar system of the trolley itself, and the manufacturing and deformation errors are quite small.

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

How the trolley overlaps the low side wall is related to the specific construction process of the construction unit. Generally speaking, users need to pour low side walls first, the specific construction process will be cleared when the trolley technology is handed over, so the corresponding marks will be made on the general assembly drawing of the trolley. When pouring the low side walls, users can refer to the trolley Assembly drawing, according to the size and location of the construction in place.

When lining, the trolley walks to the lining position and positions it. The starting point of the side mold of the trolley will be in close contact with the pre-designed lap line (surface). In order to prevent small-scale construction process changes, a 125px overlap is designed like a trolley for adjustment. During the construction of some projects, the low side walls are lined with the trolleys, and the overlap and positioning are similar.

9. Why does the die running and staggering sometimes occur in the process of trolley lining?

In the process of pouring the lining of the trolley, sometimes the phenomenon of running mold and staggering 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 fixed impact on the trolley itself;

(2) When the trolley is positioned, some of the screw jacks are not fully supported and screwed in place. When they are squeezed by external force, they are recovered, and there are gaps in the die running, which leads to a wrong platform;

(3) The structure design of the gantry of the trolley is defective, and the force transmitted by the side mold to the gantry column is too large, which causes the gantry column to retract and even deforms significantly in severe cases;

(4) Failure to deal with the existing partial radian inconsistency and lack of normal installation and after-sales service.

10. What is the reason why the concrete surface lining is not smooth? How to improve?

The lining concrete has surface roughness, pores, and poor gloss. The main reasons are two points. The air bubbles generated near the formwork during the lining process are not exhausted, and some of them adhere to the surface concrete , Causing stomata;

The second is that the concrete is too dry, and no ramming was evenly in place during the ramming, causing defects. In order to solve this problem, it may be considered to use thin-point concrete when lining the bottom side wall, and cooperate with tools such as vibrators and vibrators to perform appropriate and necessary vibrating. If a vibrator is used, the vibrating time should be controlled within 8 seconds to prevent damage to the trolley.

11. After the lining period of the trolley, why do the gaps between the templates and the amount of staggering become larger?

In the existing design, the connection between the formwork is connected by bolts, and there is a gap of 1mm between the hole diameter and the bolt diameter. When the trolley is used for a period of time, due to the use of the vibrator, vibrator, etc., the gap will be shifted, and then the fixed template gap and the wrong platform will be generated.

Therefore, I suggest that after every 5 molds are used in the trolley, manual arrangements should be made to re-tighten the connecting bolts between the formwork, and to deal with the local problems where gaps or staggers have occurred. If it is a long tunnel, you can consider welding the joints between the templates after the trolley is installed and debugged. It can also prevent the gaps between the templates and the occurrence of misalignment.

12. How to control the relative displacement between the trolley gantry and formwork when constructing large slopes?

When constructing highway engineering tunnels and hydraulic engineering tunnels, there are usually fixed cross slopes and longitudinal slopes, especially the longitudinal slope has a greater impact on the trolley. Due to the large gradient difference between the front and back, and the momentary impact force when the trolley starts, there is a tendency for relative movement between the two major components of the trolley gantry and formwork, and it will tilt when serious. In order to prevent this phenomenon, two sets of anti-deviation devices or “eight” jacks need to be added between the gantry and the template (including the upper gantry) to restrict each other, reduce the misalignment to a certain extent, and protect the use of the trolley Ann.

13. When pouring the top concrete, can it be poured through only a grouting port?

There are usually three grouting ports on the top of the trolley for easy selection and use. Under normal circumstances, use three grouting ports as much as possible to reduce the pumping pressure on the top of the trolley. However, due to the trouble of changing pipes, generally only one of the grouting ports is used, for which I disagree with this construction method. Considering the uneven construction experience of the second lining construction team, I suggest to use at least two of the grouting ports, and change the grouting ports from low to high order for grouting until they are full. If encounter reinforced concrete section, try to use three grouting ports for operation.

14. Why does the top formwork collapse or deform when the trolley is capped?

In the process of using some trolleys, especially when pouring to the top, sometimes the top template will be deformed or even collapsed. This is mainly due to the lack of experience of the second lining personnel and insufficient observation. When the concrete is poured to the top for capping, due to the high delivery pressure of the delivery pump, if the concrete is blocked due to solidification, or the reinforcement mesh is too dense, or the pouring space is filled, if no careful observation and timely stop pumping concrete, then The pressure transmitted to the formwork reaches several hundred tons or even thousands of tons per square meter, which greatly exceeds the rigidity strength that the conventional design lining trolley can withstand. At this time, it will easily cause the deformation of the top template of the trolley to collapse.

Therefore, I suggest that during the second lining operation, if it has been poured onto the top of the trolley, someone must be assigned to observe whether the trolley is full (it can be changed through the observation window and the filling pressure of the delivery pump, etc.) in order to stop in time Pump excess concrete.

15. How should the trolley be maintained and maintained?

(1) After 15 working cycles of the trolley, replace the hydraulic oil.

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

(3) The mold release agent must be applied to the template every 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 demoulding, check whether the connecting bolts are loose, and if they are loose, they must be tightened. The five-mold whisker surface tightens the connecting bolts to prevent gaps and missteps between the trolley templates.

16. What are the commonly used hydraulic oil and gear oil?

Hydraulic oil: MHM68 anti-wear hydraulic oil.

Reducer oil: hyperbolic gear oil.

Grease: ordinary butter (calcium-based grease).

17. How does the hydraulic system of the trolley seem to have no pressure?

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

(1) The hydraulic motor reverses. It can be solved by swapping the two wires of the external power supply;

(2) The valve block is faulty. It is most likely that the valve core is blocked, and the valve block can be removed and carefully cleaned to solve it;

(3) The quality problem of the hydraulic motor or the power is not matched, which can be solved by replacing the accessories;

(4) The hydraulic oil and pipeline are contaminated. The pipeline should be cleaned and replaced.

18. After a period of use of the trolley, there is an abnormal situation in the hydraulic cylinder. What is the problem?

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 work frequently, the cylinder body and rods are under great pressure, causing some hydraulic cylinders Abnormal conditions such as no pressure, oil leakage, and slow expansion and contraction greatly affected the progress of the second lining construction of the project.

The appearance of this phenomenon generally indicates that the seal of the hydraulic oil cylinder has been damaged, causing the operation rate of the oil cylinder to leak or leak out due to the internal leakage or external leakage of the oil cylinder during operation, and even unable to work normally. For this reason, it is recommended to disassemble the oil cylinder and replace the good seals.

The design of the tunnel should be based on the overall situation, comprehensively considering the requirements of the overall function of the highway, land resources, ecological environment, and sustainable development, to fully ensure that the main structure of the tunnel (slope body, gate, lining, pavement, etc.) is stable and reliable, avoiding diseases during operation happened.

In the design, people-oriented transportation service objectives should be implemented, the design principle of safety first should be adhered to, and the design concept of full life cycle cost should be established.

The overall design of highway tunnels should meet the requirements of transportation planning, environmental protection and natural landscape, and meet the service functions of highway transportation. The design speed of the tunnel, building limits, clearance section, etc. are determined by the road grade and technical standards of the road section where the tunnel is located.

Tunnel design should comprehensively consider the human environment, terrain, landform, geological and geological hazards, hydrology, meteorology, earthquake, traffic volume and its composition, operation and construction conditions in the area, and carry out technical, economic and environmental protection comparison of multiple schemes.

The choice of tunnel location should be based on the survey of topography, geomorphology, geology, meteorology, social humanities and environment, and comprehensively compare the direction, horizontal and vertical alignment of the axis scheme, and the location of the opening.

The horizontal and vertical lines inside and outside the tunnel should be coordinated to meet the safety and comfort requirements of driving.

The tunnel should be based on the geological conditions, surrounding environment, etc., to determine the cross-sectional setting form and the construction method suitable for the stratum characteristics and environmental requirements.

Tunnels are an important part of highway engineering, and tunnel design should run through the entire process of highway construction.

Tunnel-related facilities such as ventilation and disaster prevention shall be designed in accordance with the design capacity of the tunnel. However, when the design traffic volume of the tunnel is less than half of its design capacity, the design traffic control design of the tunnel can be adopted to save investment.

The design of the tunnel should be based on the structure type, construction method, use conditions and load characteristics, adopt the design concept and method suitable for its characteristics, and combine on-site monitoring and measurement to achieve information design and dynamic design.

The design of the tunnel should implement the relevant national technical and economic policies, and actively promote new technologies, new materials, new equipment, and new processes; measures should be put forward in the design to ensure the safety of construction workers and prevent production safety accidents.

Tunnel lining construction is a key construction content of tunnel engineering, which is related to construction quality and construction safety. So what are the common causes of common problems in tunnel lining construction? What control measures can ensure the quality of tunnel lining construction? The following is an analysis of the main points of tunnel lining construction in tunnel engineering, so that you can easily avoid common problems in tunnel lining construction.

Quality issues and phenomena

1.There are holes behind the lining;

2.The lining is obviously wrong, the slurry is leaking, the quicksand is serious, and the appearance quality is poor;

3.The thickness of the lining does not meet the design requirements;

4. Leakage of lining;

5.Cracking of lining concrete;

6.The appearance quality of the cable trench is poor;

7. Drainage ditch is not smooth.

Cause analysis of cavities behind the lining

1.The construction of backfilling was not carried out according to the specifications;

2. When the lining is filled with concrete, the arch is not full, and the vibration is not enough;

3. Pumping concrete is hollow at the far end of the conveying pipe due to pressure loss, slope and other reasons;

4. The looseness control of the waterproof board is not in place.

The prevention of cavities behind the lining

1. The excavation surface of the tunnel is inevitably uneven. For pits caused by over-excavation in a small area, the backfill of lining concrete is generally used during construction. Pay attention to the fact that the waterproof board should be closely attached to the rock surface, and the tightness is suitable; Deep subsidence pits should be backfilled smoothly before the second lining construction;

2. General lining formwork trolleys have one reserved pumping hole before and after the top of the arch. If the formwork trolley is longer, additional reserved holes can be added in the middle to prevent the pouring concrete from being in place when the longitudinal slope of the tunnel is large. Backfill grouting after construction;

3. The new lining formwork trolley is equipped with an attached vibrator on the side wall and arch waist. At the same time, two plug-in vibrators are provided on each side of the trolley during concrete pouring. Layer vibration, these can effectively solve the vibration problem.

Analysis of the cause of poor apparent lining quality

1. The rigidity of the lining trolley is insufficient, and the formwork is not properly repaired;

2. The lining concrete is not easy to work with, and the bleeding is serious;

3.No symmetrical pouring on both sides;

4. The pouring speed is too fast, the trolley floats up;

5. The template is too oiled, and fish scale clouds are formed after the mold is removed;

6. The partial template is not cleaned up, and the phenomenon of “skinning” and falling off is formed after the mold is removed.

Preventive measures for poor lining apparent quality

1. The lining trolleys are processed by regular manufacturers, and they have been checked for strength and stiffness before processing. Check the check data when purchasing;

2. If the lining formwork trolley overlaps less than 0.5m during lining construction, generally no misplacement will occur. Therefore, it is necessary to plan the mileage of the trolley in place before lining construction to avoid long overlaps. At the same time, surveyors should have certain construction experience, the lining center line and elevation should be well controlled, and the distance between the two sides of the formwork trolley should be properly controlled to prevent excessive and small influences from affecting the next set of trolleys in place;

3. The lining concrete is constructed strictly according to the designed mix ratio. Pumping concrete and workability requirements should be considered when designing the mix ratio. At the same time, the formwork trolley should be coated with a mold release agent. It is best to use a special mold release agent for uniform application. Moderate dosage can improve the quality of lining surface;

4. When placing the lining, it should be layered symmetrically on both sides, and the self-fall height of the concrete should be controlled within 2m to prevent segregation;

5. If there is some concrete on the formwork trolley, remove it before the next pouring, and then apply mold release agent, otherwise it will affect the surface finish of the next group of linings;

6. Due to problems such as the pressure of the cast-in-place concrete at the foot of the side wall will rise, and the end pressure will move longitudinally, the template-bed trolley is strengthened firmly before the lining construction. The lead screw is reinforced again to prevent the trolley from being displaced due to the loosened part of the lead screw.

Cause analysis of insufficient lining thickness

1. The contractor’s quality awareness is not strict, and the process monitoring is not in place;

2. Or the reserved settlement is insufficient;

3. The undercut site is not treated.

Measures to ensure lining thickness

1. The thickness of the lining should be ensured, and the initial support section should be inspected before the lining construction.

2. For some tunnels with large settlements, it is necessary to pay attention to the settlement observations. If the designed settlements do not meet the requirements, the reserve can be appropriately enlarged according to the actual situation, but it cannot be too large to prevent artificial overdigging. Waste lining hoe.

Cause analysis of lining leakage

1. Cracking of the lining;

2.Insufficient waterproofing, drainage and diversion facilities;

3. There are quality defects in the treatment of circumferential construction joints and deformation joints, and the installation of water stop strips and water stop zones is not standardized;

4. The waterproof board is damaged, perforated, and the weld is not tight

5. The lining is not compacted and there are holes or honeycombs;

6.The waterproof material is unqualified;

7. Insufficient number of drain holes or inaccessible drainage.

Prevention measures for lining seepage

The lining seepage is generally caused by the inadequate drainage and drainage construction and the lining itself is not dense. To strengthen the on-site management to ensure that the drainage and drainage measures are in place and the lining concrete is compacted, the following aspects should be done:

1. The blind pipe is installed in place. Before construction of the waterproof board, it is necessary to ensure that the blind pipe is installed according to the design requirements. The local section has a large amount of water to increase the number of blind pipes. The blind pipe and the vertical drainage pipe are well connected to ensure the drainage effect.

2. Waterproof board construction is the key link of lining waterproofing. At present, there are many types of waterproof boards on the market, and the waterproof boards must be qualified. The waterproof board connection is best to be welded. During the construction process, a quality supervisor will inspect the site and find the problem in time. deal with. Strengthen inspections on some uneven areas to prevent leakage; for reinforced concrete linings to prevent damage to the waterproofing board during the construction of the steel bar, if there is any damage, notify the waterproofing board builder to repair it; if the waterproofing board is installed, it must be close to the rock surface. , Moderate tightness to prevent tearing of the waterproof board due to pressure during pouring;

3. Treatment of construction joints and settlement joints: General construction joints and settlement joints are designed with pre-buried and buried buried waterstops or waterstops, and some have back-attached waterstops. The waterproof board can be fixed with a baffle board. When the middle-buried water-proof strip is used for construction, a small-sized cao (half the thickness of the water-stop) must be reserved in the middle of the lining end. In, fixed firmly. The construction of the middle buried waterstop requires the layered construction of the headboard, which is divided into two layers from the position of the waterstop to ensure that the waterstop is reserved and cannot be destroyed. This seriously affects the construction of the headboard, so it is often not in place. Strengthen the management on site to ensure the construction of the middle buried waterstop;

4. The horizontal drainage pipe shall be reserved according to the design, and a three-way connection shall be used to ensure that the drainage can smoothly flow into the ditch; the vertical drainage pipe is generally a perforated corrugated pipe, which is wrapped with geotextile to prevent the sediment from entering and affecting the drainage effect;

5. The lining concrete can not be stopped for a long time during the pouring process, so the site materials and generators must be fully prepared to prevent stoppages because the concrete poured twice is prone to gaps, causing the lining to leak; the only solution is to punch and grout. Water, but the holes should be shallow to prevent damage to the waterproof board;

6. The lining concrete must have a waterproof effect. Generally, it is designed as a waterproof concrete. When cooperating with the design, it must be considered from multiple aspects. It must ensure the workability and water resistance.

7. Control the self-falling height of the concrete when pouring the lining concrete, ensure the layered pouring, the layer vibration is in place, the formwork trolley window template is closed tightly to prevent slurry leakage, etc., to ensure that the concrete lining is dense and the construction concrete is waterproof.

Cause analysis of lining cracking

1. Temperature difference and dry shrinkage;

2. Alkali aggregate chemical reaction;

3.The side wall foundation sinks;

4.Body bias;

5.Cracking of the arch and side wall due to stress concentration;

6.Cracking caused by difficulty or interrupted pouring of concrete in the arch;

7. The demolding time is too early, the lining strength is not enough to support its own weight and crack.

Crack prevention measures

1. High-grade concrete hydration heat is increased, and water conservation should be carried out after construction, not less than 14d, to prevent the surface from drying and causing cracks;

2. Select qualified materials for lining concrete, and strictly follow the mix ratio construction;

3. The lining generally does not crack. Generally, the lining cracks due to bias or topographical movement at the entrance of the cave. Therefore, when backfilling the cave top, pay attention to symmetrical backfilling on both sides. For tunnels with bias, strengthen the lining strength or decompress;

4. The joint of the overhead arch and the side wall is prone to stress concentration. During the construction, ensure that the side wall foot excavation is in place, and there must be no under-excavation, which causes the lining to crack;

5. Control the lining demolding time, and formulate the corresponding demolding time and curing time according to the tunnel temperature in different seasons, to prevent the occurrence of cracking and cracking;

6. The lining concrete is guaranteed to be put in place at one time, and it cannot be stopped halfway, which is not conducive to waterproofing and easy to cause cracks and reduce the strength of the lining. Therefore, sufficient material reserves and good equipment and equipment are available before construction. Deformation, loose bolts, welding off, etc., prevent problems during the construction process, resulting in the lining cannot be properly constructed.

Cause analysis of poor appearance quality of cable trenches

1. The vertical mold is not detailed and not firm, and the outer edge of the groove is not controlled according to the center line of the line;

2.The cover plate is prefabricated and the installation quality is poor;

3. Construction in other processes, which was broken by repeated lifting, moving and collision.

Appearance quality control measures

The cable trench of the ditch is the surface engineering of the tunnel. The quality of the surface construction affects the overall image of the tunnel. Therefore, the linearity and straightness must be ensured, and there must be no wrong platforms and smooth surfaces.

1. The cable trench of the ditch is controlled for measuring and laying out, the curve is controlled according to the radius, 10m or 20m center line elevation control, and the straight line 50m control. The template adopts the overall steel template to ensure one-time pouring molding, and the template is coated with a mold release agent to ensure the appearance quality. After the template is installed, the technician checks the installation of the template, whether the linearity is up to standard, and whether the reinforcement is firm;

2. The prefabrication of the cover plate is centralized prefabrication in the prefabrication field, and the shaped steel-plastic template is used, with marks on the top and bottom for easy installation.

3. After the prefabricated cover is prefabricated, store it in the prefabricated yard. After the tunnel trench construction is completed, it will be placed in a concentrated way when there are no other processes affected. Mortar is used to fill the gap between the cover and the foundation.

Cause analysis of poor drainage ditch

1. The vertical slope of the ditch bottom is not standardized, there are deviations, and the control is not accurate. The bottom of the ditch is “wavy”;

2. The longitudinal slope of the ditch bottom is small;

3. There are debris in the ditch, and the flow path is blocked;

4. The groove bottom is uneven.

Prevention and control measures for poor drainage of drainage ditch

1. Trench excavation is in place, to ensure linearity and straightness when pouring concrete, to ensure smooth trench and prevent water accumulation;

2. There are many sundries in the hole during working hours, and it is easy to block the trench. It must be cleaned regularly to facilitate drainage in the hole.

3. Drainage Because the formwork is installed straight during the ditch pouring, the reinforcement is firm, and the compaction is used when pouring the concrete.