One of the great challenges of civil engineering is the proximity of water to engineering structures. To solve this problem, we have to remove the water from the construction site so that after the construction of the structure, water does not penetrate them. Removing water from the construction site is called drainage. Drainage literally means drying water that seeps from the ground or rocks. It is usually said that drainage prevents water from approaching the bottom of the pit and the walls of the pit and causes the sealing of the pit construction.

In order to solve the problem of providing parking in tall structures, excavation and deep digging is inevitable. Most of the following issues and problems may be encountered during drilling:

Aquifers

The proximity of semi-saturated and saturated soils

Aggressive chemical conditions

And these problems cause serious damage such as:

Water penetrates into the structure
Settlement and destruction of foundations and structural skeletons
Corrosion of steel and concrete due to the presence of sulfate or chlorine and even the phenomenon of carbonation
Increase in project time and cost
Destruction of the top of the excavation
Reducing the bearing capacity of the soil under the foundation
Side problems while running shotcrete or implementation problems like trapping machines

History of drainage

From the past until now, various methods have been used, such as bituminous insulation or asphalt for drainage and dewatering of excavations

Building pit sealing is used. But the following:

• Checking the vulnerability of these products against environmental conditions

*Uncertainty about how they work in the long term (the life of this waterproofing is short and cracks after about 5 years)

Because today these methods are used less and alternative and better methods are used for drainage and dewatering of construction excavation.

Different methods of drainage system

1) Sump pumping

The most convenient method of draining the bottom of the pit is the sump pumping method, which is done by collecting water in a sump that is usually installed in a corner of the ground and pumping it from the excavation.

2) Deep well

The deep well method consists of several wells with submersible pumps. Water is pumped from each well to the top and directed by streams or pipes to a point outside the project.

3) Well point system

A set of wells with a small diameter that is connected to a pipe at the top, and this pipe is connected to a pump at the end, which lowers the water level of the wells.

4) Trainers

In low permeability soils, water is kept away from the bottom of the pit by creating a vacuum in each well.

5) Vacuum wells

The vacuum well method is adapted from the deep well method (method 2). Water is pumped by submersible pumps and the power of the pumps is produced by vacuum pumps above the wells

6) Horizontal wells

In this method, flexible perforated horizontal pipes are used, which are installed by a special device
7) Relief wells
8) Artificial charging
9) Draining the siphon
10) Chemical consolidation of soil
11) Dewatering by building sand drains
12) Dehydration by freezing process
Sand drainage method for pit floor drainage
13) Dewatering by electroosmosis

1) Membrane dewatering method with geosynthetic products

In this method, using geosynthetic drainage layers such as geomembrane, GCL, etc., a drainage curtain is created between the structure and the surrounding environment, and the thickness of the layer is calculated based on the hydrostatic pressure of the water. Some geosynthetic products suitable for layer drainage can be named as follows:

Geomembrane sheets with water absorption properties with different thicknesses such as PVC / VLDPE / HDPE / LLDPE

GCL bentonite sheet with water absorption properties

Recessed sheet with drainage and water conduction

Geotextile with drainage and water conduction properties and geomembrane protection

In each project, based on the efficiency and characteristics of geosynthetic products, a product or a combination of different types of geosynthetic products is used for water intake and drainage of excavation walls and underground structures.

2) Dewatering method using structural members (impermeable concrete)

Different excavation stabilization methods have two different approaches for dewatering:

Stabilization with dewatering capability: dewatering diaphragm wall, sheet pile, etc

Stabilization without drainage: soil nailing, piling, etc

In stabilization methods without dewatering, assuming that the water level is higher than the level of the excavation floor, it is often necessary to dewater the foundation and retaining wall.
There are two important points for dewatering the concrete used in the foundation and retaining wall:

1) Concrete quality:

Factors affecting the quality of concrete are:

Controlling and reducing the ratio of water to cement (W/C).

Use of materials with continuous granulation and optimal filter percentage

Slump control suitable for concrete

Use of quality cement

2) Additives:

Additives lead to concrete dewatering by reducing capillary pores and concrete cracks. Here are some admixtures suitable for dehydrating concrete:

Types of water reducers and concrete lubricants

Volumetric crystallizers of concrete

It should be noted that the following are also important for complete drainage of the structure:

Correct and principled installation of water stop

Injection tube in executive joints

Suitable design for cutting concrete

Necessary controls in reinforcement and molding

Choosing the right concreting method to prevent coldness of the joint

Sealing the pit of the building in Arin Khak company

One of the most important and basic stages of building a building in Arian Khak company is sealing in its various stages. Unfortunately, in many projects, due to lack of sufficient knowledge or its economic discussion, the important stage of sealing construction pits is not done properly.

According to the construction conditions, we perform sealing in various ways, for example, if the water pressure is from behind the sealing surface, we call it negative pressure sealing, but if it is the opposite and the water pressure is from the inside. The sealing of construction pits is called positive pressure. Covered swimming pools that are located near the sea, for example

It is a sign of negative pressure sealing.

As a result, first the location should be checked completely and according to that, the sealing of the building pit should be done correctly and in place so that construction problems do not arise later.

The sealing of elevator shafts is in the category of negative pressure sealing. In many projects, it has been seen that the engineers refuse to seal the elevator shaft and do not consider surface water that penetrates as a serious problem, in the event that many problems appear later after the elevator is launched and the construction project is completed, and the use of The elevator faces a problem.

In the latest construction method, the best result is that the waterproofing should be done at the very beginning when there is no water in the walls and the concrete is fresh, so that problems such as water penetration and damage to the electrical and mechanical equipment and destruction of the wall do not occur. Many irreparable injuries can be prevented. Sealing the insulation of elevator pits is done in different ways according to the geographical location, height, number of floors and location of the elevator pit.

Contact our colleagues for more cooperation with Arin Khak company and to receive free advice in the field of building pit sealing.