What Is Slip Forming?

Sliding formwork is a form of slow-moving formwork of the formwork. Generally, it is a fixed-size formwork formwork that is towed by traction equipment.

Slipform engineering technology is our country

Slipforms not only include general or special tool-type formwork, but also comprehensive technologies such as power hoisting equipment and supporting construction processes. Hydraulic jacks are mainly used as the motive power. Under the synchronous action of group jacks, they can drive more than 1 meter high The tool formwork or sliding frame slides along the newly formed concrete surface or formwork surface. The concrete is layered and poured into the sleeve groove from the upper opening of the formwork. Each layer is generally not more than 30cm thick. When the lowest layer of concrete in the formwork reaches a certain strength, After that, the formwork slot relies on the function of the hoisting equipment to slide along the poured concrete surface or the sliding frame along the outer surface of the formwork, and then slide up about 30cm, so that the cycle operation is continued until the design height is reached, and the entire construction. Slipform construction technology, as a fast and efficient mechanical construction method for modern (reinforced) concrete engineering structures, has been widely used in various industries of civil engineering. As long as these concrete structures have a regular geometric section with unchanged boundaries in a certain direction, sliding form technology can be used for rapid and efficient construction production or production. On concrete structures with a variety of regular geometric sections, sliding form technology has shown infinite power. The construction economy and safety of concrete structures have been greatly improved, and the efficiency of construction production has increased exponentially. ^[1]

The most prominent feature of the sliding formwork technology is that the fixed formwork is eliminated, and the fixed formwork is changed to a sliding movable steel form, so there is no need to prepare a large number of fixed formwork erection techniques. , Position, and direction of reference. Strip-like structures or components are completed in one continuous construction.

The following are some of the difficulties we encountered during construction and the corresponding countermeasures:

1. The rigidity and stability of the sliding platform easily deformed platform should be strengthened

During the sliding process, due to the large diameter of the silo, the platform is also greatly affected by its own weight, construction live load, concrete friction resistance and various additional loads, so it is easy to deform. When the platform deforms, it will have a great impact on the sliding mode process. There will be a phenomenon that the platform slide height difference is too large, causing the verticality of the structure to be too poor, or the torsional deviation is serious, and even the phenomenon of unable to continue to rise. So when the platform was assembled, we took the following measures:

Control the number of lifting frames and jacks, and arrange them evenly. The distance between the jacks is about 1.2m. For special parts such as wall pillars, add jacks. When installing the lifting frame, the verticality must be guaranteed and the beam must be horizontal. The length and diameter of the hydraulic oil pipe should be basically the same, and the oil circuit should be unobstructed to ensure that the pressure is transmitted at the same time during the pressurization.

The vertical support system of the encryption platform is provided with appropriate scissors support. For vertical support, we adopt a method of sliding across the platform and encrypting across the space. At the same time, set a scissor brace every 3 ~ 4m.

Increase the diameter of the ribs on the flexible platform and increase the number of ribs. According to the size of the silo diameter, the diameter of the tie rod steel bars used is 14-16mm, and the spacing is about 1-1.2m.

2. Minimize the platform's own weight and construction load

While strengthening the rigidity of the platform, the impact of self-weight on the platform should be minimized. In other words, in the process of platform assembly, it is not as strong as possible. Because when the dead weight is too large, it will inevitably increase the load of the lifting system. At the same time, pay attention to the problem of material stacking on the platform during the lifting process. During the ascent process, the material on the platform should be stacked uniformly, and under the condition of ensuring use, the stacking amount should be as small as possible and the material should be loaded frequently. To do this, the equipment of the vertical transport must be reasonable. We have adopted two tower cranes, which are responsible for lifting steel bars, lifting rods and other materials.

3.Ensure the pouring strength of the concrete and the speed of the rebar binding

Because slipform construction requires that each slip height of the concrete pouring and reinforcing steel lashing must be completed within the prescribed unit time, otherwise the slipform work cannot be carried out continuously. When the diameter of the silo structure is large, the amount of concrete poured and the amount of steel reinforcement are much larger, and the setting time of the concrete is fixed. ^[2]