In the process of tunnel construction, the use of concrete for secondary lining is a very important work, and with the development of the times, there are new requirements for concrete secondary lining work, requiring higher quality and shorter construction period. Under the current trend, a good design of lining trolley has become an inevitable requirement.
Tunnel lining trolley and its requirements
The lining trolley is a special equipment that must be used in the secondary lining of the tunnel construction process, and is used for the concrete lining construction of the inner wall of the tunnel. Concrete lining trolley is an indispensable non-standard product for secondary lining during tunnel construction. There are mainly simple lining trolleys, fully hydraulic automatic walking lining trolleys and net-frame lining trolleys. Full hydraulic lining trolley can be divided into side-top arch type, full circle needle beam type, bottom mold needle beam type, full circle travel type and so on.
General requirements for tunnel lining trolleys
(1) The external dimensions of the formwork must be able to meet the requirements of the tunnel section. The shape error requirements are as follows: when ≤3m, not more than 10mm, when R>3m, not more than 20mm (R refers to the maximum section radius at the tunnel section).
(2) It must be ensured that the center of the formwork coincides with the center line of the tunnel. Therefore, the template can move left and right (that is, horizontally) when the main frame of the trolley does not shift laterally. Generally, the horizontal movement distance does not exceed 150mm from the centerline.
(3) The action of the template must be able to effectively complete the mold supporting, mold dismantling, and locking and positioning work. In the template trolley designed in recent years, the support and demolding of the template are hydraulically driven, and the locking is completed by mechanical devices. The overall formwork should be left with operating windows and grouting holes to meet construction requirements. The length of the overall formwork and the wheelbase of the gantry traveling wheels are related to the turning radius of the tunnel and the construction organization of other supporting machinery. The general formwork length is 6m ~ 12m, and the gantry axis distance is less than about 1m of the entire formwork length.
(4) The design of each component of the trolley should be able to meet the transportation conditions. The clearance in the main frame of the trolley should be able to meet the passing of other construction machinery.
(5) According to user requirements, the trolley has self-propelled and non-self-propelled. Regardless of the type, it should be considered that it can meet the conditions of other mechanical drag driving, and at the same time, the passing capacity of the trolley when it passes through the fork should be considered.
Design of Tunnel Lining Trolley
The design of the commonly used tunnel lining trolley formwork system needs to understand the formwork contour line, formwork lining length, work window and grouting port layout and positioning, overlap length, etc., to consider the division of the formwork, the parting situation and the release of the formwork according to the construction requirements. Die gap.
(1) Determination of the position and type of the operation window and grouting port: Arrange the grouting port of the operation window according to the requirements (the height of the bottom row of operation windows is not more than 1500mm from the side base), and the grouting port is generally closed and the outer arc surface is Flat type.
(2) Determination of the length of the panel: According to the overall design, divide the mold and determine the position of the hinge structure, but the length of the panel should not be between 5950 and 6500mm.
(3) Design of formwork panels, webs, angles and other materials: The thickness of the panel is generally between 8mm~12mm, the key points on the webs need to be arranged with corresponding bolt holes, and the appropriate reinforcement materials should be selected between the webs.
(4) The design of the mold release gap of the template: the minimum release gap is not less than 60mm (that is, the hinge between the top mold and the side mold). Generally, the design is 110mm, and the ground gap is greater than 150mm; the space for applying the release agent needs to be considered ( Not less than 350mm). There are four design schemes for the top formwork of the variable section tunnel lining trolley formwork system.
First, use a widening block at the variable cross-section of the top mold. That is to say, according to the section size of the tunnel, the smallest section size is selected as the reference section of the design. The top form is divided into two parts, left and right, which can be used directly at the minimum section of the construction, and in the construction of other widened sections. At the same time, the top mold is separated from the middle, and the top and side molds on both sides are moved to the corresponding positions at the same time. The template rose to the required height of the design.
Second, rotate the top mold and install a widening block. The design and use process of the trolley at the smallest cross-section are the same as in Scheme 1, and during the use of widening the cross-section, the top mold should be separated from the middle connection, and the top mold and the side mold should be moved outward to the corresponding position. , And rotate the top mold of the two halves around the hinge pin shaft until the end of the top mold is tangent to the designed contour line, and then install the required widening block, heightening pad, etc.
Third, rotate a part of the top mold and install a widening block. That is, according to the size of the tunnel section, the smallest section size is used as the design reference section, and the top form is divided into four pieces for design. The formwork is connected by bolts, which can be used directly in the construction process of the smallest section. In the construction of other sections, the top mold is separated from the middle, and the top and side molds on both sides are moved to the corresponding positions at the same time, and then the template on one side is rotated outwards until the end of the top mold and the design The contour lines of the tangent, and then the installation of the required widening block is carried out, and the template is raised to the required height of the design by means of heightening pads, oil cylinders or a combination of the two.
Fourth, replace all the top mold templates on one side at different sections. That is, the tangent point of the top mold at the variable section is connected by bolts, so that during the use of different sections, the top mold template on one side is gradually replaced, and the position of the side mold moves inward or outward. . When adopting this scheme, it should be noted that the connection position of the top mold and the upper mold beam in the support system must meet the size requirements of the top mold on the other side, so as to ensure the operability when changing the section.
(2) Door frame
The role of the gantry system is to support the entire formwork system and prevent the formwork from deforming and shrinking inwardly under pressure when lining the lining. The mast mainly consists of upper and lower longitudinal beams, columns, mast beams, longitudinal joints, reinforced diagonal braces, formwork beams, formwork columns, screw rods, cylinders, transversal mechanisms, walking mechanisms and other components. Among them, the gantry beam is an important load-bearing component of the formwork trolley, which requires high material strength and rigidity. Generally, the section is made of tailor-welded H-shaped steel, industrial steel, etc. For variable-section tunnels, the formwork must be moved to the outside, and the portal beam must be lengthened. When designing, you can add a widening block on one side, and move the lateral movement mechanism to the side of the widening block; or design it into two left and right blocks, add a widening block in the middle part, and the lateral movement mechanism will move with the two blocks. mobile.
(3) Hydraulic system
Trolley design lifting cylinder, template cylinder and traverse cylinder, cylinder stroke, zero stroke length, cylinder diameter and rod diameter size, pipe joint form, connecting pin hole diameter, connecting structure size, oil hole direction and external dimensions are based on the plan Determine; the working pressure of the hydraulic system is generally considered as 12MPa, and the rated pressure is considered as 16MPa. Variable cross-sections need to increase the number of joints and tubing to match this. The hydraulic system can improve the efficiency of the tunnel lining trolley and reduce the workload of workers.
(4) Other auxiliary systems
The formwork trolley should consider the traversing form of the ventilation pipe; sufficient load-bearing screws and screw rods should be provided; the vault of the formwork trolley should be equipped with concrete plugging devices and inspection holes at appropriate positions; the attachment type installed on the formwork trolley The vibrator should be able to start separately; the curve section should consider the change of the left and right side lap length caused by the difference between the inner and outer arc lengths, so as to make the arc smooth, reduce the staggered joints, and ensure the same curvature of the front and rear templates of the trolley; ensure the perfusion hole In the middle of the vault of the formwork trolley, to ensure that the concrete on both sides is poured symmetrically at the same time.
The use of tunnel lining trolley
(1) Installation of lining trolley
Due to the different tunnel construction methods, the trolley installation method is divided into two types: self-entry into the tunnel after installation outside the tunnel and hoisting in the tunnel. If installing in a hole, the excavation outline of the installation zone should be appropriately enlarged in advance, generally 50 ~ 80cm. According to the size of the tunnel section and the length of the trolley, 3~6 grouting anchor rods are set along the axis of the arch, with an interval of about 1/4 of the template length, and the ends of the anchor rods are bent into hooks to facilitate the fixed hand gourd. Due to the limited space in the cave, the transportation trolley components should be arranged in a reasonable order.
First assemble the main frame and connect the walking motor to install the template. After the top mold is assembled, lift it with a chain hoist, move the main frame of the trolley under the top mold, and install the top mold. The side form is standing on the side wall of the tunnel. After the top form is installed, it is hoisted and installed on the arch formwork with a chain hoist and connected with a pin. If hoisting outside the tunnel is adopted, the installation site should be selected to facilitate entry into the tunnel before hoisting, and the angle between the axis of the backstage car and the axis of the tunnel should not exceed 5 degrees after installation. For laying the track, the sleepers and rails must meet the requirements, and the gauge error after laying is controlled within 10mm; the track and the sleepers must be fixed with spikes to prevent danger when the trolley is walking; the distance between the sleepers must not be greater than 70cm to prevent the rails from being crushed .
When the strength of the concrete meets the requirements, remove the bottom screw support, remove the plug plate from the bottom up, loosen the lateral lead screws of each layer, and recover the part of the trolley below the hinge to separate it from the concrete; operate the lifting cylinder, Make it reach zero stroke to lower the trolley as a whole, and separate the trolley from the concrete above the hinge; at this time, the surveyor should check the clearance of the trolley. If the side form invades the traveling clearance of the passing vehicle, it needs to be re-adjusted. The stroke of the template oil cylinder meets the driving safety requirements, and the mold removal is completed. Check the status of each demoulding step. After confirming that it is in place, move the platform to the lower group of lining position; check the appearance quality of the lining concrete, analyze the cause of the problem, and perform partial repair; check whether the steel template has deformed parts for replacement; Completely remove the concrete on the surface of the formwork, and evenly apply the release agent.