Common Problems and Solutions of Lining Trolley in Tunnel Construction
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.
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:
- Installation site: depending on the size of the trolley, a stacking and installation site should be set aside, generally 20m x 20m;
- Sleepers and rails: sleepers are generally 15mm x 15mm x 800mm, and rails are 43kg heavy rails;
- 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;
- There are 6-8 installation assistants, usually by the manufacturer’s after-sales service personnel to install the trolley;
- Welding machine, gas cutting equipment, handle the connecting parts of the reinforcement parts during the transportation of the trolley;
- Wooden boards are generally required to be more than 5cm thick and are used for erecting and installing operating platforms.
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.
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.
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:
- 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;
- 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;
- 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;
- After completing the above actions, the cross-sectional dimensions should be reviewed to prevent errors.
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:
- Remove the stopper template;
- 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;
- 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.
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.
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:
- 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;
- 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;
- 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;
- The existing local arc mismatch has not been dealt with properly, and the normal installation and after-sales service treatment is lacking.
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.
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.
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.
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.
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:
- Reversal of the hydraulic motor: it can be solved after the two wires of the external power supply are swapped;
- Valve group failure: The most likely cause is that the valve core is blocked. The valve group can be disassembled and cleaned carefully;
- Quality problems or power failures of hydraulic motors can be solved by replacing parts.
- If the hydraulic oil and pipeline are contaminated, the pipeline should be cleaned and the hydraulic oil should be replaced.
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.