What is the Advantage and Disadvantage of Self-propelled Invert Trestle

Take the construction section of Ⅲ and Ⅳ perimeter rock located in the tunnel as an example, carry out mechanized supporting construction for this tunnel construction section. Design of construction technology and the development of pre-consolidation measures, from the three-arm rock drilling cart tunnel excavation, initial support, self-propelled fully braked hydraulic arch trestle elevation arch construction, second lining formwork cart lining construction and other aspects of the detailed description of the tunnel drilling, blasting, lining works of the mechanization of the supporting construction of the key technologies to ensure that the tunnel section of the construction of the construction of the task is safe, fast, high quality completion of the construction.

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0 INTRODUCTION

With the rapid development of transportation infrastructure, the importance of tunnel engineering in the transportation network is becoming more and more prominent. The development of tunnel construction technology, especially the mechanized tunnel construction technology, not only improves the construction efficiency, but also improves the construction quality and ensures the construction safety. The wide application of mechanized construction technology in tunnel engineering has promoted the development and innovation of tunnel construction technology, which makes it possible to carry out large-scale tunnel construction under complex geological conditions.

At present, tunnel mechanized construction mainly includes drilling and blasting method, shield method and road header method and other construction methods. Each of these construction methods has its own advantages and disadvantages and is suitable for different geological conditions and engineering needs. For example, the shield method has high construction efficiency and safety in soft ground, while the drill-and-blast method performs well in hard rock strata. Boring machine method is widely used in the construction of long tunnels and complex geological conditions.

In recent years, with the continuous progress of construction technology, tunnel mechanization construction technology has made significant progress in equipment performance, construction technology and management methods. In this paper, we take the construction section of Ⅲ and Ⅳ perimeter rock of Lou Shan Tunnel located in Xinbin County, Fushun City, Liaoning Province as an example to carry out mechanized supporting construction for this tunnel construction section.

1 Project Overview

The Mountain Tunnel, starting and ending mileage of DK97 +419.26 ~ DK102 +328.98, the length of .72 m. The tunnel along the route of the geomorphology of the complex morphology of the gullies and valleys across the forests and trees, dense vegetation, belonging to the high-risk tunnels.

The tunnel was mechanized in accordance with the requirements of the State Railway Group and the construction unit. According to the geological conditions of 225m of Class Ⅳ peripheral rock and 1,278m of Class Ⅲ peripheral rock in the tunnel construction section from DK100＋000 to DK101＋503, it was decided to adopt mechanical equipment such as Hong Yuan CYTJ86A3W hydraulic triple-boom rock drilling jumbo to carry out the mechanization of the tunnel's drilling, blasting, and lining works, so as to complete the construction tasks of the tunnel construction section in a safe, fast, and high quality manner.

2 Key Construction Techniques of Mechanized Supporting Construction

2.1 Construction Techniques

2.1.1 Construction Methods and Supporting Mechanical Equipment

According to the actual situation of the construction site of this tunnel construction section, referring to the relevant management methods of the construction unit, mechanized construction is carried out by adopting the full cross-section and micro-step method. According to the requirements of mechanized tunnel excavation and lining construction, Hongyuan CYTJ86A3W hydraulic triple-boom rock drilling jumbo, anchor drilling rig, self-propelled fully braked hydraulic tilt-arch trestle, tilt-arch lining cart, second lining formwork cart, excavator, loader, dumper, concrete sprayer and other required machinery and equipment are equipped to ensure that the construction of the tunnel is safe and smoothly carried out.

2.1.2 Initial support and secondary lining

Ⅳ, Ⅴ peripheral rock initial support closed into a ring position, from the palm face shall not be greater than 90m, the second lining lining safety step from the palm face shall not be greater than 160m. Ⅲ peripheral rock initial support closed into a ring position, from the palm face ≤ 150m, the second lining lining safety step from the palm face ≤ 260m.

2.1.3 Safety construction measures

Excavation according to 1:0.1 to 1:0.1, the second lining formwork trucks. : 0.1 to 1:0.2 sloping. According to the specific condition of the palm surface, take pre-strengthening measures in time to keep the palm surface stable. In micro-step excavation, the longitudinal length of the upper step is 3-5 m. According to the actual geological condition of the surrounding rock and the stability requirements of the palm surface, the longitudinal excavation length of the upper step will be adjusted appropriately.

2.2 Over-head Pre-reinforcement Measures

2.2.1 Palm Surface Treatment

According to the stability of palm surface of the construction section, the lithology of the stratum and the development of groundwater, the following measures are taken to ensure the stability of the palm surface: the palm surface is closed by spraying C30 concrete in order to improve its stability. For the unstable palm face, on the basis of spraying C30 concrete, the palm face bar is increased to further guarantee the stability of the palm face. For the palm face of class Ⅳ surrounding rock, spray 4cm thickness of concrete.

2.2.2 Super-advance support

According to the perimeter rock grade of different sections, formulate corresponding super-advance support measures, specific support measures are as follows: DK100＋625～DK100＋710 section is Ⅳ perimeter rock, adjust the original design of Ø42mm single-layer small conduit in the arch to Ø50mm single-layer small conduit, with the longitudinal spacing of 4m, the length of each one of them is 6m, and the ring spacing of each one is 0.4m, and each ring of them is 45 pcs of small conduits. The longitudinal spacing is 4m, the length of each piece is 6m, the ring spacing is 0.4m, and each ring of small conduits is 45 pieces. Drill the holes of small conduit with wind-operated rock drill, install the prefabricated small conduit, and connect orifice valve and pipeline at the end of small conduit; use grouting machine to inject prefabricated cement-water glass double slurry into the small conduit, so as to reinforce the surrounding rock of the arch.

2.2.3 Construction Requirements

According to the specific conditions of the actual construction section, the mechanized construction equipment is reasonably arranged to ensure the smooth progress of the construction process. Strictly according to the relevant norms and management methods for construction, to ensure construction safety and project quality. During the construction process, real-time stability monitoring is carried out on the palm surface, and corresponding pre-strengthening measures are taken in time according to the monitoring results.

2.3 Hong Yuan Hydraulic CYTJ86A3W Triple-boom Rock Drill jumbo Tunnel Excavation Construction

2.3.1 Construction Preparation

In order to improve the self-stabilizing ability of the surrounding rock, reduce the over-under-excavation, and save the construction cost, the tunnel excavation construction is carried out by using the surface blasting technology. Utilize the means of over-forecasting and over-drilling to detect the integrity of surrounding rock, water influx and bad geology. Analyze the basic mechanical properties of the surrounding rock and determine the actual mechanical properties of the tunnel surrounding rock, so as to determine the detailed parameters of excavation and support. Use Hong Yuan CYTJ86A3W triple-boom rock drill jumbo to carry out the drilling operation of blasting air in the palm face and use the excavator to timely clean up the stones that may be dislodged by blowing loose or generating cracks, and eliminate the dangerous situation.

2.3.2 Drilling and setting blasting holes

In view of the constantly changing conditions of the surrounding rock, designate special persons to carry out unified command and coordination, strictly control the spacing and depth of the peripheral holes, and dynamically adjust the excavation section. On-site technicians check the quality of the blasting holes drilled by the three-arm rock drill, measure and record the drilling data for backup and archiving. Over and under excavation is generally not taken into account when drilling with a three-arm rock drill.

Due to the influence of the end of the drill pipe, the end of the drill pipe should not be larger than 15cm from the excavation contour line during the drilling process, and the location of the blast holes drilled by Hong Yuan triple-boom rock drill jumbo is shown in Figure 1.

2.3.3 Charging and blasting

The charging of the peripheral holes adopts the segmented connection of the detonating cord of the non-coupling section, and simplification of steps and centralized charging are prohibited. The amount of peripheral holes must be filled in strict accordance with the blasting design program to ensure the quality of the charge. Charging should use a tamping rod to place the packet in the designated location and seal the blasting hole. Should follow the segmentation, zoning method, according to the “arch foot area, arch waist area, arch area,” the order of priority, as well as “first peripheral, then the center” order of loading.

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The order of detonation is: hollowing holes → auxiliary holes → inner ring holes → peripheral holes → bottom holes. After blasting, ventilation should be carried out to dissipate blasting fumes. After the air safety is verified, the blasting personnel should check the site for any duds or residual blasting materials, and check the stability of the surrounding rock to deal with all hidden dangers in a timely manner. The blasting hole charging structure is shown schematically in Figure 2.

2.3.4 Ventilation and slag discharge

Ventilate and exhaust the smoke in time after blasting to reduce the smoke and harmful gases. When discharging slag, one excavator and two loaders are used to work with dump trucks. Dump trucks should not be overloaded with slag, and overloading is strictly prohibited. The driver should control the speed of the dump truck, and speeding and overtaking are prohibited in the tunnel. Send someone to direct the dump truck when it passes the trestle bridge.

2.4 Initial support

2.4.1 Anchor construction and close the ring

Use anchor drilling rig according to the design spacing and length, along the edge of the steel frame to drill tunnel radial anchor holes and install anchors, weld the anchors to the steel frame, so that the anchors and the steel frame to form a complete stress ring. In order to ensure the safety and stability of the support structure, the initial support must be closed into a ring in time after excavation.

2.4.2 Connection of steel frame and installation of anchor pipe

Weld the longitudinal and transverse connecting bars of each steel frame firmly to the steel frame according to the design requirements. Install the anchor pipes according to the design requirements and control the working angle and welding quality. The base of steel frame should be solidified by concrete pads, and then sprayed concrete should be filled in tightly.

2.4.3 Construction safety and quality control

In order to ensure the construction safety, the construction is carried out in strict accordance with the specifications and design requirements to ensure the safety of each step of the process. The construction quality of the initial support is ensured through real-time monitoring and quality checking in the process of shotcrete and anchor construction.

2.5 Self-propelled fully braked hydraulic up-arch trestle lining and pouring construction

2.5.1 Structural characteristics and performance

Self-propelled fully braked hydraulic up-arch trestle is specially designed for the construction of tunnel up-arches and mainly consists of large-scale steel structural parts, with a maximum height of 1.26m, a maximum width of 4.1m and a maximum up-arch lining capacity of 12m. Self-propelled fully braked hydraulic up-arches have the characteristics of high strength, high stability and flexible movement. Stability and flexible movement and other characteristics. The self-propelled fully braked hydraulic arch trestle bridge greatly improves the construction efficiency and safety of the tunnel arch through its high-level design and powerful functions. Its flexible mobility and stable structural design make it an important equipment in modern tunnel construction.

2.5.2 Main Components and Systems

The main components of the self-propelled fully braked up-arch trestle bridge include the main bridge, the long approach bridge, the short approach bridge, the slide seat, the base, the traveling system and the hydraulic system. The main bridge is the core component of the trestle, with a length of 8m, responsible for carrying the main load and construction equipment. The long approach bridge has a length of 15m and is used to extend the construction area. The short approach bridge has a length of 6.7m, which is used to control the lifting and tilting of the trestle to ensure the perfect cooperation with the up-arch lining cart in three-dimensional space, and can be used for up-arch concrete casting and the safe passage of vehicles and workers at the same time.

2.5.3 Inverted Arch Concrete Lining and Filling Construction

Inverted arch lining and inverted arch filling using self-propelled fully braked inverted arch trestle should be poured separately. After the inverted arch lining concrete is finally set, dismantle the inverted arch formwork and pour the inverted arch filling concrete. According to the test result of setting time of concrete mixture, the pouring interval between inverted arch lining and filling concrete should not be less than 8 h. Passing of people is allowed only after the inverted arch filling concrete reaches 5 MPa, and passing of vehicles is allowed only after it reaches 100% of the design strength.

2.5.4 Pouring of inverted arch lining in cooperation with inverted arch lining cart

The self-propelled fully braked hydraulic inverted arch trestle bridge can realize highly efficient inverted arch concrete lining pouring in close cooperation with the inverted arch lining cart in the construction of the tunnel. Through the hydraulic control system, the bridge is able to adjust its position freely during the construction process to ensure the smooth progress of the pouring operation.

2.6 Second lining formwork jumbo construction

2.6.1 Requirements for track laying and machine assembly

The rails of the cart must meet the requirements of the construction specification to ensure the stability and safety of the track. The gauge error should be controlled within ±10mm to ensure the smoothness of the traveling of the cart. The track and sleepers must be fixed with road nails to prevent dangerous situations such as displacement or derailment of the cart in the process of traveling. The spacing between sleepers should be ≤70cm to ensure the bearing capacity and stability of the track. The second lining formwork cart should be assembled outside the tunnel cave, selecting the lot that is convenient for the second lining formwork cart to enter the cave, so as to ensure the smooth entry of the second lining formwork cart into the cave. After the installation of the second lining formwork cart is completed, make sure that the angle between the cart axis and the tunnel axis is ≤5°. This is the key to ensure the smooth traveling of the cart and the quality of lining construction.

2.6.2 Lifting operation

According to the conditions of the construction site of the second lining formwork cart, choose the appropriate tonnage crane to carry out lifting operation on its main parts. When lifting the main parts of the second liner formwork trolley, ensure the safety and stability of the lifting process. The second liner formwork cart is lifted and assembled according to the sequence specified in the manual to ensure the safety of the assembly process.

2.6.3 Quality control of assembly

The second liner formwork cart has been assembled and debugged in the factory before leaving the factory, so it should be assembled smoothly at the construction site. If problems are encountered, adjustments should be made with reference to the factory assembly records. If the second liner formwork is deformed due to transportation, it should be corrected as much as possible, and it is strictly prohibited to use gas cutting and welding to deal with the outer surface of the second liner formwork, in order to prevent affecting the surface finish of the second liner formwork and the quality of the second liner concrete pouring.

2.6.4 Construction Precautions

During the whole construction process, attention must always be paid to construction safety, especially during lifting and assembly, to ensure the safety of construction personnel and equipment. Every step of construction must be carried out in strict accordance with the specification requirements, especially track laying and cart assembly, to ensure the construction quality and lining effect. Regular inspection and maintenance of the cart and its ancillary equipment must be carried out to ensure its normal operation and avoid failures in the construction process.

3 Conclusion

Through the study of tunnel mechanized supporting construction process and key construction technology, the important role and practical application effect of mechanized construction in tunnel engineering are demonstrated. Through the analysis and comparison of different construction methods, the best construction plan applicable to different geological conditions and engineering needs is summarized, and key construction technologies such as equipment selection and configuration, construction parameter control, construction quality control and safety management are discussed in detail. The study shows that the mechanized tunnel supporting construction technology can not only significantly improve the construction efficiency and quality, but also maintain high construction safety under complex geological conditions.

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