How to build on quicksand. Foundation on quicksand

One of difficult situations for the construction of a building is the presence of quicksand in the soil - a mixture of soil particles and water. Quicksand, as a rule, is localized at a certain depth and, if not damaged, is quite stable. However, when trying to build a buried foundation, quicksand can cause a lot of trouble for builders.

How to build a foundation on quicksand? There are several methods, and their choice depends on the location and depth of the unstable soil layer. Therefore, before choosing any method, you must order a geological survey of the building site. During the study it is necessary to determine:

Soil freezing depth (SFD);
Groundwater level (GWL);
The depth of the quicksand and the thickness of its layer.

Methods of dealing with quicksand and choosing the type of foundation

You can fight quicksand in only one case - if it is possible to arrange a drainage system below the level of its occurrence. Quicksand is a suspension of small dusty particles of sand with admixtures of clay in water and has a semi-liquid consistency with high viscosity. High-quality drainage with water removal can dry up quicksand and prevent its further occurrence. At the same time, during the operation of the building it will be necessary to carry out regular inspections. drainage system.

The quicksand itself is not dangerous if its integrity is not damaged. Therefore, if it is not possible to drain the quicksand, it is necessary to choose a method of constructing the foundation that will avoid contact of the foundation with the quicksand, or will reduce this contact to a minimum.

If, as a result of geological studies of the soil, it was found that the quicksand is located at a significant depth, below the depth of soil freezing, for a private house you can choose a monolithic shallow strip foundation with gravel backfill, or, if the size and weight of the buildings are significant, a slab foundation on gravel-sand preparation.

If the quicksand is located at a depth of no more than 0.5 meters and its thickness is insignificant, and there are hard and stable soils underneath it, then it is better to opt for a pile foundation with a concrete grillage or using screw piles. The piles are buried into hard layers of soil by at least 1 meter, and a thickening is made at the base to prevent the piles from being pushed out by frost heaving forces.

Shallow strip foundation on quicksand

Such a foundation is made when quicksand lies at a depth of at least 1.5 meters on slightly heaving soils. If it is necessary to build a basement, it is equipped by raising the base above the ground, without deepening the underground part of the foundation.

Site preparation boils down to clearing the area, leveling it, digging a shallow pit and arranging horizontal drainage. If the groundwater level rises, drainage will prevent capillary rise of moisture. The depth of the pit is from 0.5 to 0.7 meters. The bottom of the pit is covered with crushed stone, and on top of the crushed stone - with coarse sand. Carefully compact the bedding, spilling it with water.
Formwork is made from boards or panels to the height of the basement part of the foundation. Polyethylene film or other waterproofing material is placed in the formwork to avoid leakage of concrete milk when pouring concrete, after which the foundation is reinforced in accordance with.
Fill the formwork with concrete grade M200 or higher, remove air bubbles from the concrete using a vibrator and level its surface. The maturation of concrete lasts for at least 28 days, during which time the foundation must be protected from precipitation and direct sunlight.
After the concrete has dried, it is necessary to waterproof the foundation, and, if necessary, insulate it, after which the pit is backfilled with sand.

Slab foundation on quicksand

Used in the case of deep-lying quicksand on heaving and wet soils. called floating - its design allows it to withstand a significant load of the building, and during frost heaving and soil movement, the foundation moves along with the entire building, without deformation.

The site is leveled and backfilled with crushed stone and sand to a height of up to 0.5 meters. They compact it tightly, spilling water. Make markings. Laying underground communications.
Horizontal hydro- and thermal insulation of the base of the slab foundation is carried out: a layer of expanded polystyrene insulation is placed on the prepared backfill, and roll waterproofing is placed on it.
The formwork of a slab foundation is made of boards or plywood panels, the height of the formwork is about half a meter. The prepared surface is covered with plastic film, gluing the joints of the strips with tape. The film prevents the leakage of concrete and concrete slurry from the formwork; in addition, it will ensure the mobility of the slab in the event of soil movements.
Reinforcement is performed using a corrugated rod with a diameter of 12-16 mm, laying it in a grid with a pitch of 15-20 cm. At the intersections, the rod is knitted using wire. In order for the reinforcement to be completely recessed in the concrete, the rod must be laid on plastic guides.
Concrete is poured into the prepared formwork, leveled and compacted using an in-depth vibrator and vibrating screed, and smoothed using the rule. Concrete takes 4 weeks to dry, during which time it must be protected from precipitation.

Pile foundation on quicksand

Such a foundation is made if the quicksand is located at a close distance to the soil surface, but its depth is small, and below there are solid, stable layers of soil. This situation is typical for wet silty sandy loams, when groundwater is shallow. They feed the quicksand, and drainage turns out to be an insufficient measure to drain the soil. Therefore, the only way to create a sustainable and reliable foundation is the deepening of piles to the depth of solid soils.

Site preparation comes down to clearing it of vegetation, debris and marking.
Piles can be used both concrete and screw steel. The second option is preferable because of the price; in addition, screw piles can be easily installed without the use of special equipment. The advantage of screw piles is also that their installation occurs simultaneously with drilling, which means that there is no need to take measures against flooding of the well and pump out water if the quicksand is damaged.
Piles are installed in the corners of the building, at the intersection of walls, and also every two meters under load-bearing walls. The metal piles are screwed together using a lever inserted into special ears, checking their verticality and level. Concrete piles are driven using special equipment.

Metal piles are screwed into solid ground and continued to be buried at least a meter. If necessary, they are increased. Excess steel piles are cut off with a grinder, and strapping is attached on top: from metal structures - for welding, from wooden beam– using special heads.

Safety precautions

During any excavation work in an area with quicksand, it is necessary to take measures against the breakthrough of quicksand. If its integrity is damaged, flooding of the pit can occur in a matter of seconds, and getting out of the viscous mass is very difficult.

Therefore, when working it is necessary:

Strengthen the walls of the pits with boards;
In a pit more than a meter deep, install a ladder that provides quick access to the top;
All work must be carried out by a team of two or more people.

In areas where the soil is predominantly sandy, or where there was once a river or lake, the developer can expect an unpleasant surprise in the wetlands - the presence of quicksand in the soil. Quicksand is sand or sandy loam saturated with water. The problem is that it is fluid and liquefies under load. What kind of foundation to build on quicksand, what to pay attention to in such a situation - we will talk about all this in this article.

Construction of the foundation of a house on quicksand

Despite the fact that sand is often used as a material for a cushion (read about sand cushions), its presence in the soil can negatively affect the foundation. It all depends on the size of the sand particles. As you know, sands are not only coarse and medium in size, but also fine and dusty. The latter pose a danger if they are present in the ground at a construction site. The fact is that when saturated with water, they acquire the property of fluidity, which negatively affects the bearing capacity of such soil. The situation is aggravated by clay impurities, which are usually found in quicksand. Considering the low resistance value of wet sandy-silty soil (see the table below), the location of the base of the foundation on quicksand is unacceptable.

How to find out that we are dealing with quicksand

It is impossible to do without geological research. It is best to order engineering and geological surveys from a professional company before starting construction. But if you decide to make the foundation yourself, then you can save on similar services:

if your neighbors on the site have already built a house, there is a high probability that they have the necessary information on the soil. The easiest option is to ask them;
independent exploration of the soil under a future construction site comes down to digging a pit to a depth not lower than the GPG or drilling wells. The presence of quicksand will be indicated by the sliding of the pit walls and the filling of the well with a pasty mixture of “liquid sand”;
If quicksand is found during soil research, it is almost impossible to independently determine the thickness of the fluid soil layer. Those. considering a foundation on screw piles or a columnar foundation buried below the quicksand as the basis of the house, you will have to fork out for professional services

Foundation options

In general, if we're talking about When it comes to building a house on a site with quicksand, almost all types can be considered as its foundation - it all depends on the specific conditions:

a pile foundation with a grillage is suitable in cases where the thickness of the quicksand is known and it is insignificant. Driven reinforced concrete piles or screwed steel products can be used as supports. The idea is to place the base of the foundation below the quicksand. The supports are tied with a reinforced concrete grillage;
a strip shallow foundation can be used in two cases: the quicksand is at a significant depth (more than 3 m) or it is possible to install a drainage system for the foundation. The last option is convenient on a site with a slope - by draining the quicksand, we simply neutralize its negative properties;
A slab foundation is most often used in cases where the load from the house is significant and the quicksand is located not far from the surface of the earth (1-2 m). In these situations, savings on the installation of the above types of foundations look dubious, so the slab is poured

Precautions when working with quicksand

Imagine a balloon that is filled with water and tied. As soon as you pierce it, water will immediately rush out. The situation is similar with quicksand: they behave more or less predictably while they are in the soil and access to them is limited by the overlying layers. Once the “shell” is pierced, flowing sand will break free. Therefore, when developing pits (or deep trenches) for the foundation, in places where quicksand can be detected, it is necessary to work at least together: one is engaged in excavation, the second is monitoring the process.

In general, building a foundation on quicksand is associated with the same difficulties that occur when working with any other heaving soil. Whether you are building a foundation on peat, clay, loam or sandy loam, you always need to take into account the ability of such moistened soils to swell throughout their entire thickness along the GPG. Therefore, preference is usually given to monolithic structures that can adequately respond to local loads.

A foundation on quicksand is a building on soil that has fluidity. This is where the word “quicksand” comes from. Such areas of land are very fragile and can liquefy when exposed to various workings.

Quicksand has various impurities and is saturated with moisture. It is a soil made of sand or loose rocks – sandy loam.

Types of quicksand and quicksand properties

Depending on the type of soil, quicksand exhibits quicksand properties. They are determined by the density of the rock, the size and shape of the particles, mineral and granulometric composition.

Floats can be:

True (clayey sands, loams, sandy loams);
Pseudo-quicks or false ones (gravelly sands).

In true quicksand, clay particles have high hydrophilic properties. These soils absorb moisture well and are characterized by molecular intensity of interaction. In the floating state, a wet film forms around the particles. The filtration coefficient is minimal (0.005 -0.0001 cm/s).

The true composition can sometimes be determined by external signs. “Cement milk” accumulates at the bottom of the well. The soil taken from the bottom spreads into a cake. There is another way to determine buoyancy. They drill sand and water plugs. High porosity will cause the holes to fill with water. Swimming abilities can be most accurately determined in the laboratory.

With true floating soil, the hole is filled with dirty milky water. Clay gives it this color. When they dry, the clay particles stick together and create a very strong mass.

The floating layer makes it very difficult installation work during construction. During excavations, a layer of earth tries to fill the empty space. Creating a closed loop is very difficult. If there were such a possibility, the deposit would be a solid foundation. If the float goes beyond the base area, failures and landslides occur.

Open drainage is dangerous, as it can cause soil subsidence.

In false quicksand, particles of gravel and sand do not have structural connections. They become liquefied due to water pressure. The water at the bottom will be light, slightly cloudy. False quicksand easily give up water. And when they dry, they create a loose mass.

Before making a house on quicksand, you need to carefully determine the content of the soil in order to find out the type of floating earth, as well as its properties.

Fighting quicksand

The fight against a floating layer is a complex process, from which a positive result is not always obtained.

Methods for dealing with the layer:

Method of artificial drying;
Creation of fences with sheet piling walls;
Conversion physical properties from fastening the quicksand.

Artificial drainage is carried out by open pumping of water. If it is necessary to dry the ground to a depth of 6 meters, wellpoints are used, and at a depth of more than 15 meters, special parts with electric drainage are used.

When fencing with sheet piling walls, they cut the entire layer of quicksand. This allows all the pressure to pass through you. A wooden tongue and groove is driven to a depth of 5-9 m, and a metal sheet pile is driven to a depth of up to 30 m. If there is a layer of dense soil, it will not be possible to drive a tongue and groove.

The interlayer is fixed by cementation, freezing and silicatization.

Freezing is an unreliable method. This method uses frosty weather conditions or special installations.

Silication is very effective method. It involves pumping liquid glass into the soil.

For truly weak layers, only the following fastenings are used:

Electrochemical;
Freezing;
Fencing.

Floating land is most often located in marshy areas. It is difficult to carry out work in such places. Therefore, the walls are strengthened when a pit or trench is dug. These works are mandatory.

Types of foundations on quicksand

The depth and thickness of the fragile layer play a role when choosing the type of construction base.

There are:

strip foundation on soils with a layer of quicksand;
pile with grillage;
monolithic.

Shallow foundation is the most commonly used type for shallow floating layers. Excess water is removed using drainage. In some cases, the slope of the terrain is used.

For the construction of heavy houses, a monolithic foundation is used. The thickness of the slab is calculated in a specific example. The essence of this method is constant pouring of concrete. Reinforcing bars are used in formwork to provide strength to the structure.

If the quicksand under the foundation is small in width, then piles are used under the structure.

For shallow deposits, the bulk method is sometimes used. Sand or gravel is brought to the site and the site is covered. Then construction is erected on this foundation.

During installation work, safety precautions must be observed. The layer can manifest itself unpredictably as soon as the layers that held it back are disturbed.

Foundation planning

You can explore the land yourself. To do this, you need to dig the soil with your own hands or drill wells using equipment. If a mushy mixture appears at the bottom of the pit, and you can notice how the walls are sliding, this will mean the presence of a creeper in the soil. For help, you can turn to the owners who have a house nearby and already know the characteristics of the soil.

To determine the exact composition of sediment in the soil, you will have to turn to specialized research. And only after this can you begin to lay the foundation of the house on quicksand.

A pit is dug and soil is removed. If the pit is filled with a large amount of water, it is pumped out using pumps. If there is little water, then they resort to a drainage system.

As soon as the well is dried, it is necessary to immediately concrete the base thinly. Then it is covered with a drainage composition (crushed stone, screenings). After this work, everything is concreted. This will prevent soil subsidence after the construction of the structure. Within a week, the concrete will harden and waterproofing can begin.

Foundation for shallow quicksand

If the quicksand lies at a shallow depth of up to 2 meters, then a strip foundation on the quicksand is used for construction.

The construction of the foundation occurs in stages:

Preparing the base. Clearing the soil surface, digging, arranging a drainage system. The pit is dug to a depth of up to a meter, then filled with drainage. Everything is filled with water and compacted;
Laying formwork no more than half a meter high;
Pouring concrete. Hardening it within a month;
Carrying out work on waterproofing and insulating the base.

To calculate a shallow foundation, you need to know the deformation and bearing capacity of the earth.

Pile foundation with grillage on quicksand

This type of house foundation on quicksand is used in those territorial areas that are often flooded. The pile method with a grillage will allow you to raise the structure to a height of up to 3 meters from the soil. Therefore, during a flood, the first floors are not flooded.

There is a bored and driven installation method. With the driving method, a construction drill breaks through the funnel. Depending on the loads on the building, the required number of pillars is calculated. It is advisable to maintain a distance of up to 1 meter between the pillars.

At a height of more than 2.5 meters, a grillage is laid. Its width should not extend beyond the outer wall by more than 50 cm. The tape is reinforced using long rods. Their size should cover the entire wall.

The pile foundation on quicksand is very reliable and durable. It is also built in unfavorable geological areas where there are landslides and karsts.

Features of building a house made of foam blocks on quicksand

Often a house is built from porous artificial stone. Building such a house is inexpensive.

The foundation on quicksand for a house made of foam blocks can be strip or pile. If the soil is not heaving, a shallow foundation is laid. Choose this type to reduce concrete costs. It is important that the entire surface, both the strip base and the ends of the pillars, are on the same plane.

The blocks have a porous structure, and at the slightest slope they will begin to crack. Depending on which foundation is suitable, the proportion of concrete is calculated. When drilling, soil samples are examined at a frequency of 15 cm. Drilling must be carried out in several places. This will allow you to more accurately determine the location of fragile deposits in the ground.

Quicksand, as is known, is the name given to soil saturated with water, capable of freely spreading (“swimming”) in the thickness of the earth. In its composition, this formation resembles a thick mixture with a high degree of viscosity, consisting of groundwater, clay and sand. Preparing a foundation on such soil will require the contractor to have certain knowledge and skills in carrying out excavation work.

Before making a decision on the future foundation of the structure, it is necessary to carefully examine the composition of the soil at the site of the proposed construction. To carry out such research, it is best to invite specialists, which will allow you to avoid errors in calculations. In addition, you can get all the necessary information on the actual composition of the soil from your neighbors on the site (preferably from those who have recently completed construction of a house).

As for independent exploration of the site, you can explore the soil by drilling a well (using the means at your disposal) or after manually opening it in depth. In this case, the presence of quicksand in the pit will be indicated by the appearance of a liquid mixture of clay and sand in the excavation, as well as a strong sliding of its walls and subsidence of individual sections of the earth. In addition, during a comprehensive survey you should obtain all the necessary data regarding such characteristics of the site being developed, such as:

freezing depth of water-saturated soil;
data on groundwater occurrence;
the thickness of the above-mentioned soil (the depth of its location).

Based on this data, you can choose the type of foundation that would meet the basic design requirements. Of all the possible options for independent arrangement, the following types of support structures seem realistically feasible:

strip foundations (with a soil depth of no more than 1.5 meters);
support based on reinforced concrete slabs;
grillage pile foundations.

Using a strip foundation

If the thickness of the quicksand is less than 1.4 meters, you can use the option of preparing a shallow strip base. To implement this project, first of all, you should prepare a trench about 0.6-0.7 meters deep, the bottom of which is covered with a layer of crushed stone and sand (i.e., the so-called “cushion” is prepared). In addition, you will need to dig a drainage ditch located next to the future building (at a depth just below the base of the latter).

To do this, you will need to prepare another trench, laid parallel to the main one. The bottom of the drainage ditch is also covered with a bed of gravel and sand, on which a layer of geotextile is then laid. Sewage pipes are placed on top of the material, with direct access to a special inspection well, which makes it possible to carry out preventive measures. At the end of the work, the trench with the drainage elements laid in it is covered with a layer of sand and gravel.

The construction of a foundation trench begins with the preparation of internal formwork, for the manufacture of which ordinary boards or ready-made panels are used.

The open walls of the formwork must be lined with roofing felt, which plays the role of waterproofing.

Preparation and pouring of concrete is carried out in accordance with generally accepted rules and regulations stipulated in the relevant documents.

Preparation of slab and grillage bases

The advantages of slab-type foundations include the following distinctive characteristics:

ability to withstand increased loads;
absence of deformation under significant temperature changes;
Possibility of use on wet soils with deep occurrence of quicksand.

It is recommended to use a monolithic slab in the construction of large buildings, an example of which is a multi-story brick house. In this case, the dimensions and other technological parameters of the monolith must be selected taking into account the individual characteristics of the project being implemented.

It is necessary that the concrete base is poured continuously, and reinforcing bars with a diameter of 13-15 mm are used to strengthen it.

The foundation can also be prepared using so-called grillage piles. This category of supporting products includes such well-known structures as modern screw and driven reinforced concrete piles. The main thing you need to pay attention to when arranging them is right choice the place where the sole of the structure is fixed, which should be located below the level of the soil itself, saturated with water.

Video

You can opt for screw piles. For more information about this device method, see below:

The construction of a foundation on quicksand is a complex process, since here it is necessary to take into account the specifics of the deep occurrence of soil layers that are supersaturated with moisture. Need to design construction works in such a way as not to disturb extremely unstable formations.

This special type of soil is based on water and fine-grained sand; this buoyant mass (which explains the name) is not suitable for heavy loads. If the foundation is not designed correctly, the house can sag significantly. There are true and false quicksands.

True Origin

This soil consists of loam, clayey sand, sandy loam, and exhibits high hydrophobic properties. The soil quickly and abundantly absorbs water; the particles are characterized by molecular interactions. Quicksand can be recognized by a specific film that has a minimum degree of purification. To determine the essence of the soil, you can use external signs: “cement laitance” appears at the bottom of the well; when a sample is removed from there, the latter instantly blurs. To accurately verify the presence of such soil on a site, the sample must be examined in the laboratory.

A hole dug in such an area will quickly fill with water, and the liquid will have a reddish tint. As it dries, it forms a dense, viscous mass. Such a floating layer can complicate installation work, since during the construction process soil can penetrate into any recesses. In such conditions it is more difficult to form a closed circuit.

False origin

The main component in this case is gravel sand. The formations are not as dangerous as in the previous case, since the composition does not contain strong molecular bonds. The liquid that appears at the bottom is usually light; it evaporates quickly, resulting in the formation of a loose mass.

Types of acceptable foundations for quicksand

In such difficult conditions, specialists design strip, slab and pile foundations. Each of the varieties is appropriate in specific situations, which will be discussed below.

Tape

If the quicksand is located no deeper than 1.5 m in soil of a slightly heaving type, the optimal solution would be a shallow strip foundation. In the case where the building design includes a full basement, the base is arranged in such a way that it rises above ground level (here additional structures cannot be immersed in the soil).

Slab

Such a base is advisable in a damp and heaving area, if the unstable layer is deep enough. The costs of materials and installation work in the case of a slab foundation will be significantly higher compared to a strip foundation. But such a solution is characterized by high stability and impressive operational capabilities.

The second name of the construction technique is floating foundation. During frosts and heaving of the soil, such a foundation can withstand serious loads, since it is able to shift along with the structure without causing damage to the latter.

Pile

If the quicksand is close to the surface, the only safe option is to install a pile foundation. This option will be appropriate only if there is a dense, stable layer under the water-saturated layer. The conditions correspond to wet silty sandy loams, which are extremely difficult to drain, so it is easier to install piles.

Advantages of the solution:

versatility – can be used in all types of soil;
the ability to organize work without reference to weather conditions;
high load-bearing characteristics;
limited list of required earthworks.

Compared with strip foundation, the cost of pile construction is almost half as much.

How to make a foundation on quicksand: technologies and rules

Construction instructions completely depend on the chosen type of foundation, and therefore it is worth giving detailed guide regarding each option.

Construction of a strip foundation

After examining the site, drawings of the future structure are drawn up, which indicate the thickness, dimensions of the segments, and features of the fill. The area is cleared of debris and vegetation, leveled, and a pit is laid on it.

To prevent capillary rise of water from below, a horizontal drainage system is introduced. The maximum permissible pit depth is 70 cm, a crushed stone cushion is created at the bottom, and the top is covered with coarse sand, moistening and compacting it.

The height of the formwork must correspond to the future base; it is made of metal, laminated boards or plastic; it is most convenient to use collapsible variations. The cavity is filled with roofing felt or waterproofing film, and reinforcement is performed.

For pouring, high-quality concrete is required; when introducing it, vibrators are used to get rid of air bubbles. The surface is leveled and left to thicken for at least 26 days. The foundation must be covered with film to prevent the destructive effects of the sun and precipitation.

When the concrete has dried, you can begin waterproofing and insulation measures. Next, the pit is filled with sandy soil.

Technology for creating a slab foundation

The design drawing is drawn up taking into account the specifics of the site. The thickness and size of the optimal slab, the method and location of its placement are calculated. The working area is cleared, leveled and covered with a 50-centimeter layer of crushed stone. The workpiece is thoroughly compacted and soaked in water. The area is marked using a cord and stakes.

Lay underground sections of sewer and water supply lines. Before pouring the base, all thermal insulation and waterproofing measures are carried out. A bedding consisting of polystyrene foam and insulation is placed on the workpiece, and it is covered with rolled waterproofing.

The formwork is formed from panel boards or boards with a height of at least 50 cm. The material must be durable and able to withstand heavy loads due to the weight of the concrete. The prepared surface is covered with polyethylene so that the joints can be fixed with tape. Thanks to the film, the concrete solution will remain inside the formwork and will not leak out. Such a slab will be movable in case of soil heaving.

Reinforcement is performed using corrugated rods, the diameter of which is in the range of 1.2-1.6 cm. The material is laid in the form of a mesh, and the joint areas are strengthened with wire. The reinforcement is placed on plastic guides and must be completely immersed in the solution.

The formwork is filled with concrete and, after leveling, a vibrator is applied to it. The rule will help straighten the surface. If the weather is dry and warm, the solution will dry within 3-4 weeks, in cold conditions it will take up to 6 weeks. To prevent getting wet, the foundation is covered with polyethylene.

The top layer of approximately 10 cm is removed from the area, markings are created on it in accordance with the previously drawn up drawing. Depending on the type of quicksand, the future weight and dimensions of the building, the optimal number of piles to be introduced is calculated.

Experts suggest using metal or concrete structures; the first option is most often used. Installation of metal piles is simpler, has a lower cost, and their efficiency and reliability are not inferior to concrete ones. Steel piles are installed without the use of special equipment; all manipulations can be completed in a couple of days.

Screw modifications do not require preliminary drilling; during the process of screwing them into the soil, there is no risk of flooding; there is no need to pump out water. All implementation points are indicated in the drawing, special attention is paid to corner areas, areas forming the intersection of walls, and load-bearing structures.

Screwing in steel variations can be done by 2 workers using a special rotary lever. During the process, the evenness of the insertion is constantly monitored. Concrete piles require the use of technology.

After the hard layer is reached, the pile is immersed another 1 meter. The structure can be expanded as needed. To remove excess you will need a grinder. At the final stage, a piping is installed for the introduced piles.

Precautions when working with quicksand

If a water-saturated formation is accidentally damaged, there is a high risk of its breakthrough, in which case flooding of the pit is likely. The essence of quicksand resembles a balloon filled with water - when sealed, the product is not dangerous, but during a rupture the flow cannot be controlled.

To minimize adverse effects, you must follow the recommendations of professionals:

strengthen the slopes of trenches and pits with wooden panels;
assign one of the workers to monitor from an elevated position all stages of work on the site, so that in the event of an emergency he can take emergency measures;
install a ladder in a convenient place that will allow you to quickly climb to the surface if a gap occurs.

To prevent problems from arising later, it is necessary to carefully examine the area being built. A professional study will help reveal the soil conditions; based on the information received, an economically justified and safe construction algorithm is selected.

Ways to deal with quicksand

To build the foundation of a house on quicksand, you need to choose the best of three methods:

formation of fences from sheet piling walls;
fixation of the area where unstable soil occurs;
artificial drainage.

In the latter case, open pumping of water is organized. If the formation is located at a depth of no more than 600 cm, it is better to use wellpoints; if the level is lower, electric drainage devices will be needed.

Sheet piling walls are capable of blocking the layer of quicksand, they create pressure leading to containment of the load. A tongue and groove board is inserted into the soil up to 10 m; if metal products are used, it can be placed up to 35 m. This method cannot be used if there are dense layers of soil near the quicksand.

Quicksand can be fixed by three methods - freezing, silicatization or cementation. The most effective is silicatization - in this case, liquid glass is pumped into the soil, which helps to increase the strength of the base and eliminate soil mobility. Freezing is extremely unreliable; even after exposure to powerful refrigeration units, the quicksand will soon thaw.

An obligatory step is the creation of a complete drainage system lying below the problem level. Quicksand consists of small particles united by water, drainage helps dry this area, and the soil structure gains strength. During the operation of the building, it is important to periodically audit the system - this is a key safety measure.

If the quicksand is below the soil freezing level, it is permissible to install a strip monolithic base with a shallow backfill; here, a gravel backfill will be a mandatory element. If the quicksand is located below 50 cm from the surface and has insignificant thickness, you can install pile foundation(there must be solid soil under the aquifer).