Construction methods and technical points of tunnel body excavation in tunnel engineering, potential

The excavation of the tunnel entrance is planned to adopt mechanical construction, and the excavation of the tunnel body uses a simple self-assembling trolley to drill the hole, and the multi-section millisecond detonator is detonated, in order to improve the smooth blasting effect of the peripheral eye, the peripheral eye is detonated with a special detonator. The tunnel ballast is loaded with a loader, and the dump truck cooperates with the ballast. The secondary lining concrete pouring of the tunnel uses an integral large formwork trolley with a length of 12m, and the concrete is mixed in a centralized manner at the mixing station, transported by a concrete transport vehicle, and pumped into the mold.

The side ditch construction adopts composite steel formwork.

1) Arrangement of temporary facilities for tunnel construction: Due to the planned single-end excavation at the tunnel entrance, the temporary facilities for tunnel construction are arranged on the right side of the tunnel exit. According to the topographic conditions of the cave entrance, the air supply machinery and equipment are arranged outside the roadbed on the right side of the exit, and the reservoir is located on the left side of the cave top about 80m away from the cave entrance.

Immediately after the mechanical entry into the site, the excavation of the earth and stone at the entrance of the cave, the construction of the slope interception ditch at the top of the cave and the reinforcement of the slope anchor spray slope surface, and the preparation for the excavation of the hole.

2) excavation and reinforcement of the opening: adopt mechanical construction, excavate according to the subgrade earthwork construction method, when digging to the stone section of the opening, in order to reduce the disturbance of the slope of the cave entrance and the subgrade slope as much as possible, the method of weak blasting or pre-cracking blasting must be used to excavate. The slope of the cave entrance is reinforced with hanging net spraying concrete, so as to facilitate the safe entry of the hole.

3) excavation and support of shallow section of surrounding rock at the entrance of the cave: the construction method adopts the step method construction, the upper step adopts the advanced hollow grouting anchor, the upper arc guide pit circumferential excavation leaves the core soil method, the excavation is the same as the distance between the steel arch and the excavation of each cycle, the initial support is applied in time after excavation, the first step excavation is 8 10m behind the upper step, the initial support and inverted arch are implemented in time after excavation, and then the middle rock column is grouting and reinforced.

4) Excavation and support of similar surrounding rock and similar surrounding rock deep buried section:

The surrounding rock is excavated by the step method, and the first step is 8 10m behind the upper step, and the initial support application of the upper and first steps must be followed by the excavation.

The surrounding rock is excavated by the full-section method.

5) The excavation of all kinds of surrounding rock adopts simple self-assembling trolley drilling, and the loader cooperates with the dump truck to transport the ballast.

In order to ensure the safety and stability of tunnel construction, the principle of "weak blasting, less disturbance, short excavation, strong support, diligent measurement, and tight lining" must be followed in the construction of weak surrounding rock sections, and the following measures should be taken in the construction

a, each excavation cycle footage to the design of the two steel frame spacing as the limit, and immediate support, in order to achieve the purpose of short excavation, strong support;

b. Adopt short step method excavation to facilitate fast ballast and fast circulation;

c. Strengthen the monitoring and measurement of surrounding rock, analyze and process the measurement data in a timely manner, so as to facilitate the pre-control of the next stage of construction, implement dynamic technical guidance for tunnel construction, and ensure the safety of construction and the stability of the tunnel;

D, according to the surrounding rock dynamics and excavation prompted by the engineering geological conditions, the geological changes of the special bad section can be further taken to strengthen the support measures, such as infill steel support, spray selfish concrete to close the face of the tunnel, advance anchor, small steel pipe, small conduit grouting temporary inverted arch bottom and other effective measures for comprehensive treatment.

Hello! In the construction process of water conservancy and hydropower tunnel project, the construction unit should carry out a comprehensive understanding and analysis according to the construction site, and the construction personnel can use the form of step excavation technology to carry out comprehensive construction for the special construction site. However, during the construction process, the construction personnel should protect the site accordingly and slowly excavate the stone earthwork in the form of steps; In the excavation process, the construction personnel should carry out a comprehensive control of the height of the steps, the length of the general steps is 50 80m, forming a closed ring form, and maximizing the construction quality of the water conservancy and hydropower tunnel project.

In the process of excavation and construction of water conservancy and hydropower tunnels, the smooth blasting technology will be affected by external factors, resulting in tunnel collapse and deformation. Therefore, in the construction process of water conservancy and hydropower tunnel engineering, the technical form of tunnel excavation should be effectively utilized and analyzed, especially the technical form of smooth blasting. In the process of tunnel engineering construction, the form of blasting and mechanical equipment excavation is mainly used to carry out comprehensive excavation work on the tunnel body of the tunnel project, and in the process of smooth blasting, the construction personnel carry out comprehensive polishing of the rock surface.

In the construction process, the construction personnel should carry out comprehensive protection work on the tunnel body, and carry out smooth blasting work from the center, but reserve the corresponding core soil rock pillar during blasting and excavation, and the height of the general soil rock pillar is 5m. In the tunnel body excavation process, reserve the corresponding protection thickness, usually its thickness is about 70 100cm, and then in the form of using artificial smooth surface blasting excavation, as an auxiliary construction technology, finally form the form of the ring ratio, ensure the smooth development of the tunnel body excavation construction process.

Safety precautions for tunnel construction:

1. Tunnel construction should be regarded as the focus of safety standard site construction, carefully compile site safety implementation standards, make comprehensive planning, reasonable arrangement, standardize command behavior, operation behavior and on-site production facilities, and implement standardized management.

2. Ventilation pipes, high-pressure air ducts, water pipes, lighting lines, power transmission lines, transportation roads, and pedestrian roads should be planned in a unified manner, and maintenance should be strengthened, so that they are neatly laid out and in good condition. Machinery and equipment should be stored in a fixed position, materials and tools should be stacked neatly, and a special person should be responsible for safekeeping.

3. The construction should be under the unified command of the foreman on duty, and the excavation, lining and transportation operations should be reasonably arranged according to the construction organization design to reduce interpolation and mutual interference.

4. Blasting excavation should be designed for blasting, and parameters such as peripheral eye spacing, extrapolation angle and charge must be strictly controlled by smooth blasting or pre-cracking blasting technology, so as to reduce the disturbance of the surrounding rock and the number of over-under-excavation.

control the stability of the side slope;

Choose a reasonable construction method, and at the same time strengthen the temporary support.

Summary. Advance anchor: construction in the tunnel arch before section excavation, generally divided into advanced hollow grouting bolt and advanced mortar anchor, the direction of the anchor is the forward direction of the tunnel, the advance anchor generally passes through the arch, and is welded with the front and rear rings in advance, and forms an overall force with the arch to prevent the collapse of the tunnel section arch.

Radial bolt: also known as system bolt, tunnel bolt, radial, as the name suggests, is a kind of anchor along the radius of the tunnel center, generally requires the anchor to be perpendicular to the rock surface during construction, under normal circumstances, the angle of the arch part of the bolt is not easy to control in the actual construction. What it does:

Stabilize the rocks within the area of action of the bolts.

What factors should be comprehensively determined by the excavation method of tunnel body.

Advance anchor: construction in the tunnel arch before section excavation, generally divided into advanced hollow grouting bolt and advanced mortar anchor, the direction of the anchor is the forward direction of the tunnel, the advance anchor generally passes through the arch, and is welded with the front and rear rings in advance, and forms an overall force with the arch to prevent the collapse of the tunnel section arch. Radial Anchors:

Also known as system anchor, tunnel body bolt, radial, as the name suggests, is a kind of anchor along the direction of the radius of the tunnel circle, generally requires the anchor to be perpendicular to the rock surface during construction, under normal circumstances, the angle of the arch part of the bolt is not easy to control in the actual construction. Purpose: Stabilize the rocks within the area of action of the bolt.

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