Grid panels are an important means of strengthening tunnel excavation and excavation. Reasonable selection during the construction process can accelerate the construction progress. According to different cave cross-sections and address conditions, different forms of support can be used to effectively reduce project costs. It can accelerate the support of damaged areas in caves, ensuring the stability and construction safety of cave structures.

The grid plate is a steel frame reinforced support system, mainly used to support the surrounding rock pressure and suppress deformation before the sprayed concrete does not meet the design strength or cannot be sprayed in time. It improves the initial support system resistance, ensures the safety of construction inside the tunnel, and becomes a part of the permanent support system under later support, which is conducive to the stability of the cave structure.

The grid plate has a large contact area with concrete, good bonding effect, can deform together, act together, and is not prone to shrinkage cracks. The grid plate is produced using flexible steel, and the installation should be as suitable as possible for the rock wall. The integrity is better, and the rear part is not prone to cavity problems.

It has relatively low cost, good economy, light weight, and convenient transportation and installation. However, the grid plate and overall stiffness are low and cannot resist the deformation of surrounding rock stress and other defects.

Many steel grating procurement personnel require manufacturers to quote based on weight when inquiring about prices, but which weight is it? It is easy to have many misunderstandings in the middle. According to the industry standards for steel grating, there is a theoretical weight and a weight that the product can bear after production. There is a difference between these two weights, and it is important to distinguish them clearly when requesting pricing based on weight. Below, we will provide some comments on the difference between the actual weight and theoretical weight of the steel grating plate.

The theoretical weight of steel grid plate (referring to the theoretical weight calculated according to standard materials after edge wrapping and surface treatment). Due to the differences in edge wrapping, opening, and cutting, there will be differences between the actual weight and the theoretical weight. The theoretical weight is calculated based on detailed quantities, and there is a difference between the actual weight and the actual weight, which is within the specified scale. Therefore, the theoretical weight and actual weight of steel grating panels are different.

1、 Flat steel error:

The flat steel used in the production of steel grating plates has a lower tolerance, and the commonly used flat steel actually conforms to national standards, so there will be some component distance on the flat steel. 2、 Twisted square steel error

The application of twisted square steel also has certain limitations, so there may be some distance on the twisted square steel, which will affect the practical weight of the steel grating.

The original plate refers to a semi-finished product sold directly by a steel grating pressure welding machine after welding, without undergoing segmentation or hot-dip galvanizing treatment. The original steel grating is generally sold in foreign markets, and dealers in other countries are generally used as inventory. According to the needs of their domestic customers and the specific conditions of use, they are divided, hemmed, and hot-dip galvanized to make it a finished product for sale. This method can greatly save processing time, greatly increase packing volume, and reduce shipping costs.

The original steel grating board is generally 1m x 6m, 1m x 5.8m. Surface hot-dip galvanized or untreated, 6m steel grating is suitable for loading 40 foot containers, and 5.8m is suitable for loading 20 foot containers. The width and length can also be adjusted according to customer needs. Suitable for on-site cutting and dealer sales. The original board is divided into edge wrapped and non edge wrapped types, which are made according to customer requirements. If it is used for cutting, it is recommended not to edge wrap to save costs. The original packaging is usually bundled with straps, and then fumigated wooden blocks are placed between the bundles for easy loading and unloading. It can also be used as a chassis.

Quality specifications and requirements

The steel grating board must comply with the YB/T 4001-2007 Chinese Steel Grating Board Standard of the People's Republic of China; The material complies with the Chinese steel standard GB 700-88; Galvanization meets the Chinese hot-dip galvanizing standard GB/T13912-2002. (Note: The platform plate and trench cover plate are cut from the original plate, and the welding quality and dimensional tolerances of the grid plate are consistent with the original plate. This statement is not repeated.)

1. The length tolerance of the steel grating plate is (0, -5mm), the width tolerance is ± 5mm, and the diagonal tolerance is ≤ 4mm Others meet the requirements of the national standard YB ／ T4001.1-2007, and the distance from the Fried Dough Twists steel center at both ends of the product to the product edge is 50mm (tolerance is ± 5mm);

A. The spacing between flat bars is 30mm, and the width is 995mm or 993mm (the thickness of flat bars is 5mm or 3mm)

B. The spacing between flat bars is 40mm, and the width is 1005mm or 1003mm (the thickness of flat bars is 5mm or 3mm)

C. The spacing between flat bars is 60mm, and the width is 965mm or 963mm (the thickness of flat bars is 5mm or 3mm)

2. The load-bearing flat steel must be straight, evenly spaced, cut flat, and without any misalignment;

3. Between the cross bar and the flat steel, there should be no missing or faulty welding. A 120kg force should be applied to test whether the Fried Dough Twists steel is soldered off. Individual open solder joints should be ≤ 3%;

4. The head of the crossbar should be flush, and the size of the head protruding from the outer load flat steel should be less than 1 millimeter. The polishing of the crossbar head should not damage the flat steel of the steel grating body.

5. The welding method is pressure welding. The height of the solder joint shall not be higher than 1.5mm on the upper end face of the flat steel;

6. The weld seam must be full, and the appearance of the weld seam must be smooth without any false welding phenomenon.

7. The product should not have welding gaps and should avoid acid water leakage at the weld seam as much as possible. If it is severe, the product needs to be replaced.

8. The product cannot have strokes (including chalk) on it.

9. According to customers

1. Prepare raw materials

The steel grating produced this time adopts Q235B flat steel with a width of 40mm and a thickness of 3mm, with a spacing of 30mm. The spacing between the horizontal bars is 50mm.

2. Welding of steel grating

The welding of steel grating is mechanical pressure welding, which uses a high-voltage resistance welding machine. The mechanical arm automatically places the crossbar horizontally on a uniformly arranged flat steel, and through strong welding power and hydraulic pressure, the crossbar is pressed into the flat steel to obtain a steel grating with firm welding points, stability, and extremely high strength.

Manual welding requires punching holes on the flat steel first, and then placing the crossbar into the hole for electric welding. There will be gaps between the crossbar and the flat steel, and not every point can be welded, so the welding is not firm and the strength will be inferior to mechanical welding.

3. Cutting

According to the dimensions in the steel grating drawing, the entire steel grating after welding must also be mechanically cut. (Introduction to Efficient and Energy saving Steel Grating Cutting Machine) Strictly control dimensional errors during cutting. After cutting, professional quality inspectors conduct sampling inspections on the already cut steel grating, and re cut the unqualified steel grating.

4. Welding of end plates (edge plates)

The material and model of the flat steel in the end plate and steel grating are the same, and manual welding is used for welding. During welding, the oil and dirt on the surface of the steel grating should be removed before welding, and the weld seam is a single-sided fillet weld. Each flat steel of the steel grating needs to be welded to the end plate. After welding, remove slag from the surface and polish it smooth.

5. Hot dip galvanizing

Hot dip galvanizing is an essential process for steel grating. Before galvanizing, sandblasting or shot blasting should be chosen to remove surface rust, ensuring that the surface is free of oil, rust, and other dirt.

The average weight of the zinc layer after galvanizing shall not be less than 460 grams per square meter, and the quality after galvanizing shall comply with the provisions of GB/T13912.

6. Packaging and transportation

The above steps are the complete production steps for steel grating. After the construction is completed, prepare the supply list, and then package, load and transport all the steel grating plates.

During the production of steel grating, it is necessary to deal with water, electricity, gas, and flammable and explosive materials. In order to prevent fires, explosions, and other safety accidents during work, certain safety production requirements must be made.

1. Fire prevention

It is necessary to regularly inspect the wires on the production site for aging, damage, and short circuits, check whether the oil in the oil tank overflows, whether the mooring temperature is safe, whether the cooling circulation system of the steel grating is working properly, and check whether the fire extinguishing tools on site are complete and working properly.

Acetylene cylinders must be stored safely

2. Explosion proof

The acetylene and oxygen used during construction are both flammable and explosive gases. If not handled properly, it is very easy to produce open flames and explosions. Therefore, for flammable and explosive gases and liquids, strict adherence to operating procedures is necessary. For damp tools, workpieces, or steel grating, if placed in a heating furnace (salt bath furnace) without drying, any expansion of water vapor can cause explosions or splashes, which can easily burn workers. Therefore, any tools and parts entering the furnace must be dry.

3. Antivirus

Barium chloride and nitrite used in heat treatment are toxic, and the toxic gases produced during high-temperature heating and the wastewater produced after production can pose great harm to human health. So the operators of the steel grating must wear protective clothing and gas masks, and there must be ventilation equipment on the construction site. After work, attention should be paid to the cleaning of tools.