Technology of production of works using the "wall in the ground" method

In modern megacities, the trend towards more rational use of space and densification of buildings is increasingly being traced. These circumstances dictate to construction companies certain conditions. On the surface, there are fewer and fewer free sites, which forces developers to resort to the erection of underground structures. Among other things, there are some objects that are more rational to erect underground. This includes large warehouses, shopping and entertainment complexes, as well as garages. But underground construction is a rather laborious process, which provides for the availability of certain experience and appropriate equipment from construction companies.

The solution of the problem described above can be complicated by the fact that the soil is very heterogeneous, there may be voids of different sizes, underground water currents. Sometimes, when surveying the territory for development, it turns out that the breeds are rather weak. It happens that under the ground are all kinds of tunnels of engineering systems that are not mapped. At the same time, it is often necessary to work in crowded conditions, since the foundations of neighboring buildings are located quite close to the construction site, and the walls of high-rise buildings do not allow the cranes to fully rotate.

Solution of the issue of construction of underground structures

Depending on what are the hydrogeological characteristics of the terrain and how deep the rooms will be, underground construction can be carried out in one of several ways. The most common are the "wall in the ground", the method of the lowered well, as well as the open method. The first technology in modern realities is quite common and still continues to rapidly gain popularity, because with its help you can solve the problem in cramped conditions without bothering the foundations of the buildings located nearby.

Principle of technology

The wall in the ground is built on a fairly simple principle, which involves the preparation of trenches and excavation of soil. Further in the formed voids are built enclosing structures, for this, as a rule, reinforced concrete is used. Under the protection of the received systems, internal structures are installed, for example, the floor and other elements.

Varieties of the method

The technology "wall in the ground" can be divided into several subspecies, such as: trench and pile. The first is the use of monolithic concrete and reinforced concrete sections, through which a single wall is formed. The piling method involves the installation of bored pillars, which are located in a continuous row. They allow to form a strong enclosing structure. Whichever technology is used, it is more promising than alternative methods of erecting underground structures. It is advisable to use it when reconstructing existing buildings of any purpose.

Application area

A wall in the ground can be used when there is a need to erect anti-filtration curtains, underground tunnels, garages, warehouses, underground passages, reservoirs, various sedimentation tanks, automobile interchanges, and foundations of buildings for different purposes.

Wet and Dry Methods

Given the strength of the soil and the level of its moisture, builders can choose a wet or dry method of construction. The latter is not so expensive, because for him there is no need to prepare a clay solution. However, it can only be resorted to when there is confidence in the strength of the ground and the absence of underground currents. Wet technology is the ideal solution for erecting large objects in water-saturated unstable soils. If the construction is accompanied by the described conditions, then sometimes there is a need for additional reinforcement of the walls of the trench. In the long run, strong and reliable premises are obtained.

Thixotropy

When a wall in the ground is arranged, the technology can provide for the use of a wet method, in which the concept of thixotropy is important. This property is inherent in the clay solution, which has the ability to restore the original shape without mechanical influences. Due to this, the correctly selected suspension will gain strength during the construction phase and liquefy from vibrational effects. This allows you to insure the walls of the trench from deformation. The highest possible thixotropic qualities are found in bentonite clays.

If we consider the additional characteristics of such solutions, we should pay attention to their water-repellent quality. After the slurry solidifies, hydrostatic pressure will act on the wall surface , which promotes the formation of a waterproof film. Its thickness can vary from 1.5 to 5 millimeters, this is enough to protect the structure from water. Claying the walls allows you to save on the water loss of the pile driving. This is one of the many advantages of the described technology.

Applied equipment

When a wall is created in the ground, the technology provides for the use of appropriate equipment. It allows you to dig a trench. To do this, the most frequently used device is a continuous device. Similar results can demonstrate a cyclical approach. For the formation of a trench, earth-moving machines are commonly used, namely bucket, planing, milling, dragline, rotary and percussive drilling rigs, grapples, and backhoes. The listed equipment will be enough to get a wall in the ground, which can be deepened by 100 meters. The conditions can be completely different. The "wall in the ground" method most often assumes that the width of the trench will be equal to the limit of 1 to 1.5 meters. In some cases, projects are made in which the width reaches 2 meters.

Cases of inexpediency of methods

Undoubtedly, the described technology has a lot of advantages, but we can distinguish situations when the use of the method is impractical. The construction of a "wall in the ground" is not performed if there are strong underground currents in the soil, with loose soil, and also when there is a dilapidated masonry on the site. Do not use technology when there are metal islands, as well as large pieces of concrete. When there are voids and cavities in the soil, you should not start work on the technology described.

Anti-filtration air curtains

Manipulations for the creation of anti-filter curtains can be considered as simple as possible. They are carried out using heavy and hard clays, as well as monolithic concrete. The purpose of the veils is to protect the object from water. Most often, such elements are used for equipping dams and digging trenches. In the latter case, air curtains are necessary to prevent the penetration of water into the cavity. The workers will not face the task of lowering the groundwater level, which is a rather laborious procedure. If we compare the curtain with the lowering units, then the latter act temporarily while the work is being carried out. Constructions in the presence of veils will not be afraid of the most powerful flows of groundwater.

Capture Options

Before the foundation "wall in the ground" is built, it is necessary to calculate the length of the clamp. This parameter will be affected by several factors, among them:

• Stability of the trench;
• Structural features and functional purpose of the structure;
• The type of technique used to develop the trench;
• Calculated intensity of concreting.

Technology of work

The erection of the wall in the ground begins with the drilling of the well, then trenches are prepared, which are simultaneously filled with the solution. The next step will be the installation of reinforcing cages, as well as a concrete pipe. Final manipulations involve the displacement of the clay solution by feeding the concrete mixture through a vertically moving pipe. Trenches can be designed for the entire length or for individual sections. The reinforcing cages are based on steel rods with corrugation. The resulting system should be less by 12 centimeters in comparison with the width of the trench. Elements are wetted in water before installation, as this reduces the amount of adhering clay and increases adhesion to concrete.

Concreting

The construction of a wall in the ground involves concreting, which is carried out by the method of the pipe being moved. The latter has a diameter ranging from 270 to 300 millimeters, while the thickness of the walls is 10 millimeters. Considering the volume of the pipe, the neck is selected, and the wads can be made of burlap.

Seizure Restraints

The construction of a wall in the ground may imply a deepening of the trench by 15 meters or less. In this case, use pipes, whose diameter is 50 millimeters less than the width of the trench. 5 hours after the concreting, the elements must be removed, and the resulting cavities are filled with a mixture. If the depth of the trench is greater than the mentioned parameter, there will be a need to install a limiter. Its task is carried out by a sheet of metal, which is reinforced to the reinforcing cage. Canvas can be strengthened by welding beams to it.

Increase in productivity

When the "wall in the ground" method is used in the process of building a fairly large object, and the length of the seizure is more than 3 meters, it may be necessary to supply a concrete mixture of huge volumes. In this case, it enters the pipes, and for a faster and easier laying, the plasticity of the solution is increased by plasticizers. The composition is poured in such a way that its surface covers the entire structure by 10 centimeters. This is required in order to be able to subsequently remove the contaminated layer of concrete, because it will have a large amount of clay. Sealing will need to be done with the help of special equipment, which is strengthened on the concrete pipe. If its length is more than 20 meters, it is recommended to use two vibrators.

Those pipes that will be on the border of the seizure are always extracted. It is important to correctly determine the extraction time. If you do this too early, then the edges of the shell may be damaged. If the extraction is too late, the pipe may become stuck between the concrete and the ground. In order to exclude such processes, it is often necessary to use sheet iron instead of a pipe, with the help of which it is possible to create unrecoverable strong bridges. They need to be welded to the reinforcing cages. To protect the mouth of the trench from deformation and shedding, it is necessary to equip the foreshatch, which is the head of the trench.

About ground pressure

If it is necessary to know what the ground pressure is at the depth z, then the following formula can be used: PR = PS + PQ, where PS is the lateral pressure intensity at the indicated depth from its ground weight, taking into account the bedding, water action, and effective Coupling; PQ is the intensity of the lateral pressure at the said depth from the loads on the surface. If the forkshaht project is located on a specially formed dump above the ground surface, the value is assumed with a minus sign.