Solving the problem of high ground water
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IOP Conference Series: Earth and Environmental Science
PAPER • OPEN ACCESS
Solving the problem of high ground water
To cite this article: P A Shustov and A A Bobrova 2021 IOP Conf. Ser.: Earth Environ. Sci. 751 012082
View the article online for updates and enhancements.
This content was downloaded from IP address 46.4.80.155 on 16/09/2021 at 19:08Baikal Forum 2020 IOP Publishing
IOP Conf. Series: Earth and Environmental Science 751 (2021) 012082 doi:10.1088/1755-1315/751/1/012082
Solving the problem of high ground water
P A Shustov1,2 and A A Bobrova2
1
Department of Construction Production, Irkutsk National Research Technical
University, Lermontov str., 83, Irkutsk, 664074, Russia
2
Department of Industrial and Civil Engineering, Angarsk State Technical University,
Tchaikovsky str., 60, Angarsk, 665835, Russia
E-mail: shustovpa@mail.ru
Abstract. During the construction of buildings and structures, as well as during operation, it is
often necessary to carry out a set of measures to reduce the level of ground (underground) water.
This is due to the frequent occurrence of dangerous natural and man-made processes - flooding
of built-up areas, which cause adverse changes in the natural and man-made environment. The
article discusses the main methods of water reduction, in order to choose the optimal and rational
method of work during the construction and operation of buildings and structures. When
choosing the most effective and optimal method of water reduction, it is necessary to take into
account not only the physical properties of the soil, but also the technical, technological and
economic aspects of the problem being solved.
As a result of frequent floods, there is a problem of increasing the level of ground (underground) water
due to flooding of territories. Flooding is a rise in the level of underground water, which leads to
disruption of economic activity in a given territory, changes in the structure and function of natural
biogeocenoses. In June 2019, a flood (flooding) occurred in the Irkutsk region, caused by an increase in
the water level in rivers. In the zone of flooding hit areas such as Nizhneudinsk, Tulun, Taishet and
others. As a result of the flood, such objects as administrative buildings, hospitals, schools,
kindergartens, highways, as well as engineering communications were damaged. Of the 1,092 cities in
Russia, about 70% are flooded, which leads not only to contamination of ground water with heavy
metals, oil products and other pollutants as a result of sewage leakage from sewer networks, but also to
increased seismicity of built-up areas. Man-made flooding is especially dangerous because it is hidden
in nature, its development provokes the occurrence of landslides, karst, etc. [1].
The water table is affected not only by natural processes, but also by the occurrence of accidents
related to the human factor. Man-made flooding begins during construction and continues during the
operation of urban areas. Man-made activities lead to increased groundwater supply due to leaks from
water-bearing utilities and various waste filtration reservoirs, infiltration of sewage and irrigation water,
condensation of moisture under structures and asphalt, construction of engineering structures, creation
of ponds and reservoirs that cause underground water retention. Increased nutrition, especially due to
industrial wastewater leaks and the creation of artificial reservoir reserves, causes negative changes in
the quality and a significant rise in the level of ground (underground) water. All this also leads to
flooding of the territory. Thus, a new anthropogenic aquifer has been formed on the territory of the
Gorky agglomeration for 20 years, the area of which has increased 4 times over 15 years of observations,
and the level rise has been 10 m. Infiltration losses from reservoirs, numerous ponds, leaks from water-
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Published under licence by IOP Publishing Ltd 1Baikal Forum 2020 IOP Publishing
IOP Conf. Series: Earth and Environmental Science 751 (2021) 012082 doi:10.1088/1755-1315/751/1/012082
bearing utilities and irrigation of green spaces in Moscow led to an overall increase in groundwater
supply by more than 3 times.
The process of flooding is multi-factor, formed under the influence of both man-made and natural
factors that change the level of water quality, water regime and balance of the territory, which leads to
an increase in the level of underground water and soil humidity.
Due to the constant increase in the ground water level, there is a need to use various methods of water
reduction in the construction and operation of buildings and structures. Water reduction – artificial
lowering of the underground water level. It is achieved by pumping or diverting water to low places and
is called "construction water supply".
The construction water supply system is a set of devices and facilities designed for receiving,
pumping and discharging underground water during the construction period, as well as works performed
sequentially for their construction, commissioning and maintenance.
The purpose of water reduction works is either to lower the natural level of underground water, or to
divert the water entering the pit (trench) in various ways that protect it from flooding [2].
The formation of systems for lowering ground water occurs with the use of drainage from pits and
trenches, drainage, open and vacuum wells for water reduction, needle filters and electric
dehumidification, used in various combinations in the form of linear, half-ring, ring, systematic,
individual and group devices for water reduction.
There are open drainage and ground or deep. Open drainage is most advisable to arrange in the
following cases:
- in cohesive soils with inclusions of thin sand layers and lenses;
- in unconnected dense soils that will not be loosened or washed away (under the influence of ground
water or filtration currents);
- in layered soils with an average flow rate of ground water, etc. [3].
To choose the right method for drainage, it is necessary to study the hydrogeological features, terrain,
size of the pit (trench) and other parameters.
The accepted method of mechanized development of ditches and trenches can have an impact on
construction water supply. Two methods of excavation are usually used. The first is the development of
soil by earthmoving machines and mechanisms with its preliminary drainage. The second is the
development of soil by means of hydro - mechanization with subsequent drainage of ditches and
trenches [4].
Accordingly, the order of work is assigned not only for the development of pits and trenches, but
also for the installation of drainage and water-reducing installations and their operation.
There are three ways of dewatering, depending on the place where it is carried out:
- surface (the necessary equipment is laid from the ground surface);
- underground (the necessary equipment is laid from underground workings);
- combined (equipment is laid from the ground surface and from underground workings).
Underground and combined methods of water reduction are most often used in the mining industry,
as well as in the construction of metro lines. The surface method, in turn, is the most common.
The main methods of protection of pits (trenches) from penetration of ground and other waters are:
- open methods of water dewatering;
- closed methods of water dewatering;
- special methods of ground water retention;
- compaction (ramming) of the soil [3].
Open and closed methods refer to the surface method of water reduction. The closed method is
divided into: gravitational water removal, vacuum water removal, and electroosmotic water removal. A
special method of retaining underground water involves a method of pneumatic water removal, and the
method of compaction of the soil is a compaction of the walls or bottom of the pit. With an open method
of water dewatering, ground water is collected in specially arranged catchments (zumfs), from which it
is pumped out using the necessary equipment. The method is applicable in stable unconnected soils and
cohesive loose soils in cases where: - in coarse - grained soils, the flow of water into the pit can be
2Baikal Forum 2020 IOP Publishing
IOP Conf. Series: Earth and Environmental Science 751 (2021) 012082 doi:10.1088/1755-1315/751/1/012082
removed by technical means; - in fine-grained soils, the necessary water reduction is possible; - there
are no unacceptable mechanical deformations of the soil.
The open method should not be used when the average size of soil particles is less than 0.1 mm
(otherwise, pit slopes may collapse, changes in the soil structure or hydraulic water breakthrough into
the pit may occur, and precipitation of existing structures located near the pit is likely). As a rule, the
open method of water dewatering is used when it is necessary to slightly lower the ground water level.
Closed method of water reduction. With this method of water dewatering, water is pumped out of
the receiving wells, resulting in a decrease in the level of underground water around the pit and a
decrease in the inflow of ground water into the pit. The process of removing ground water from
permeable layers can be carried out by various methods:
- gravity (if the flow is under the action of the pressure of groundwater table and water enters the
suction wells under the action of gravitational forces);
- vacuum (removing water from the soil is performed by means of an additional pressure reduction);
- electroosmotic (in fine-grained permeable soils, movement of groundwater can be enhanced by
creating a constant electric current magnetic field) [3].
The method of closed water dewatering, in comparison with open, is the most effective when the
ground water level is significantly lowered. Also, when using it, suffusion and soil erosion are unlikely.
This method mainly depends on the water permeability of the soil.
The gravitational method of water dewatering consists in the fact that as a result of pumping water
from special wells (wells), a level drop occurs, which causes water to flow into the well, under the
influence of gravitational forces, and a corresponding decrease in the level of underground water. This
is achieved by removing (pumping) ground water from a system of tube wells, boreholes, or needle
filters.
The system, which includes water intake wells and a drainage system of pipes, is an installation for
lowering the ground water level. Due to the operation of the pumps, the movement of ground water is
ensured.
In permeable soils with a filtration coefficient from 2 to 50 m/day, the needle filter method of gravity
water reduction is used.
The use of water-reducing wells in fine-grained soils of medium water permeability is average
effective, since the lowering of the ground water level is significant only near the wells, and the depth
of water reduction between them is small. Therefore, in such cases, it is necessary to use a different
method of water reduction. In this regard, it is considered that the use of the gravitational water reduction
method is ineffective if the average grain size of the soil is less than 0.06 mm [3].
However, the gravity method of water reduction can be used with greater efficiency in medium and
large silty and fine-grained Sands, with filtration coefficient values from 10-4 до 10-5 m/s.
Vacuum method of water reduction. In cases where the gravity method of water reduction, for
technical and technological reasons, can not provide the necessary level of lowering of underground
water in fine-grained Sands, the method of removing ground water by vacuuming is used.
The inflow of ground water to the well, when using the vacuum method, is provided by the formation
of a low - pressure zone in it in one of the following ways:
-wells with vacuum pumps;
- needle filters and vacuum pumps;
- ejector system of water dewatering;
- installations of electroosmotic water reduction - needle filters with vacuum pumps [3].
The optimal application area of the vacuuming method, when it is most effective, in medium and
large silty and fine-grained Sands corresponds to conditions where the filtration coefficient value lies in
the range from 10-5 to 10-7 m/s. For filtration coefficient values from 10-4 to 10-5 m/s, both vacuum and
gravity methods can be used with the same efficiency.
In low - permeable soils, depending on the filtration coefficient, it is rational to use:
- with a filtration coefficient of up to 2 m/day, a vacuum method of water reduction should be
implemented using vacuum wells;
3Baikal Forum 2020 IOP Publishing
IOP Conf. Series: Earth and Environmental Science 751 (2021) 012082 doi:10.1088/1755-1315/751/1/012082
- with a filtration coefficient from 2 to 0.2 m/day, the needle filter method of vacuum water removal
is used (if necessary, it can be used in soils with a filtration coefficient of up to 5 m/day, but with less
efficiency);
- with a filtration coefficient from 2 to 0.2 m/day at a depth of lowering the ground water level to
10÷12 m, and with a certain justification - up to 20 m, a needle-filter ejector method of water reduction
is used.
The method of vacuum water reduction is especially effective in soils that are located to the formation
of quicksand.
Electro-osmotic method of water reduction. For silty fine-grained and medium-grained soils with
low plasticity, the electrochemical changes of which do not exceed 15-20 %, an electro-osmotic method
of water reduction is used. Such soils behave similarly to soils with a high content of silty particles,
which are located to the formation of quicksand, but can not be drained by vacuum water reduction.
Equipment and materials required for electroosmotic water treatment:
- metal anodes;
- needle filter, which is the cathode;
- electrical installation and equipment;
- direct current source; - pumps and pipelines [3].
The movement of ground water, when using electroosmotic water reduction, is carried out under the
influence of an electric field formed by a direct current. For technical use of this physical principle,
pipes (or rods) are lowered into the ground along the perimeter of the pit, and needle filters are used as
cathodes.
It should be remembered that changing the position of the ground water level has a negative impact
on the condition of the soil. The effects of dewatering occur to varying degrees, depending on the
conditions of dewatering and the characteristics of the soil, for example:
- changes in the bearing capacity of the soil due to the action of installations that change the ground
water level;
- if the ground water level is deeply lowered, the precipitation of the territory and structures built on
it may be significant;
- when deep water dewatering occurs, local compaction of the soil occurs, which can affect the
foundations of neighboring structures (cause their precipitation);
- in the course of work, it is possible to loosen the soil and break the strength bonds in them (violation
of the natural properties of the soil);
- with open drainage, significant filtration through the pit slopes is possible, which weakens the
strength bonds in the soil and causes the removal of soil particles, etc.
The solution to the problem of flooding, which causes an increased level of underground water, will
be to choose a rational method of water reduction or search for an alternative method of lowering the
ground water level.
In practice, the needle-filter method of water reduction is more often used not only in construction,
but also in emergency response and restoration work on drainage networks located in watered and
weakly resistant soils. Ground water is pumped out using special needle-filter units for vacuum
dewatering [5].
It should be remembered that when choosing the most effective and optimal method of water
reduction, it is necessary to take into account not only the physical properties of the soil, but also the
technical, technological and economic aspects of the problem being solved. For example, geological and
hydrogeological profile; the depth to water level; the duration of dewatering; traffic conditions of
groundwater prior to commencement of works; the location of the pit (trench) existing structures;
existing technical means and installations for water dewatering. Each of these methods has its
advantages, it is important to consider the economic feasibility of the method we choose.
4Baikal Forum 2020 IOP Publishing
IOP Conf. Series: Earth and Environmental Science 751 (2021) 012082 doi:10.1088/1755-1315/751/1/012082
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