Common problems and solutions of tunnel lining trolley construction

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.