What is seepage?

In hydrology, when water flows down in a pore or crack of unsaturated soil due to gravity, the deep layer of soil is called seepage. It is the slow movement of water in the soil layer. Seepage is mainly found near hydraulic structures and is responsible for the stability of earthen-type hydraulic structures.

Principles and applications of seepage

Seepage study plays a key role in civil engineering and geotechnical engineering as its applications are vast and its principles are used in most of the phenomena and theories of soil mechanics which is a subject of civil engineering. Seepage occurs when there is a difference in water levels on both sides of the structure. It is very important to calculate the quantity of seepage and permeability in seepage analysis. A book named "Principles of seepage" by Lakshmi N. Reddi, John Wiley & sons, and Hoboken, published in hardcover gives a detailed description of the principles and applications of seepage flow in civil engineering, agricultural sciences, and soil. The preface of the book contains an introductory description of the applications of the seepage in various areas of civil engineering. For instance, in geo-environmental, the designing of subsurface seepage barriers is done, in geotechnical engineering, drainage is estimated for earth dams, in transportation also drainage in the subsurface pavement is calculated. Lakshmi N. Reddi conveyed in the book, how the seepage is calculated in two manners:

1. Seepage quantification is done in a manner that includes solving mathematical solutions with numerical modeling or analytical solutions.
2. This manner includes a qualitative approach which has very less rigorous mathematical solutions and closed-form analytical solutions.

Factors affecting seepage flow

Hydrologists give various factors which affect seepage flow, seepage velocity, and seepage force in various soil parameters. These factors depend on fluid level and movement in the soil. Factors affecting seepage flow are:

• Permeability: The property by which the soil particles allow fluid to pass through them is called permeability. The degree of minute gaps between soil particles that let air or water percolate through it is called porosity. Porosity is the number of empty holes a material contains. Both these parameters play an important role in holding water content and seepage flow because without these parameters water could not flow through non-porous media.
• Hydraulic conductivity: Hydraulic conductivity is the layer affecting the seepage flow. It is the conduction through pore and gap between the soil structure eventually affecting the density and viscosity of flowing water.
• Water pressure: When the groundwater rises, the water content in the soil also rises increasing the water pressure in the soil. Due to which seepage flow occurs and water is forced inside the walls or foundation of the structure. This happens when the soil is in a state of saturation.
• Precipitation: The more rainfall occurs, the more chances of seepage flow will take place.
• Infiltration: The maximum amount of water that can enter the soil is termed infiltration capacity. When the infiltration capacity of soil increases, saturation also increases leading to seepage.

Effects of seepage flow

• The major effect of seepage flow is seen in dams and tunnels because seepage weakens the stability of the structures leading to failure of the structure.
• Seepage is required in underground water as it fills the aquifers and wells.
• Seepage principles help in filter technologies. When water flows in between the soil layers it tends to form a filter media resulting in the cleaning of the water.
• Water seepage in buildings results in settlement of the building or sinking of foundation resulting in collapsing of the structure.
• Upward movement of seepage results in minimizing the effective stress which results in quicksand condition.

Treatment of seepage and applications

The movement of water flow in soil has to be governed and calculated because it influences the stability of civil infrastructures. The water dissipated in the soil has to be controlled in a manner that one can provide safety to the buildings and dams. For that, one needs drainage and seepage control for subsurface structures. By providing proper drainage systems near the structures or building, dewatering can be done which can solve the problem of seepage in the walls of the foundation. As one provides engineered layers for percolation of the seepage flow in the soil, keeping the vadose zone in mind, water can be restricted from entering the walls of the structure. Many seepage control systems with drainage systems and waste containment zones can be introduced while the construction of the structure.

Seepage control systems can be designed using principles of mathematical solutions which provide us with derivations from field applications. Many hydrologists approached mathematical, analytical, and numerical modeling of the seepage control system and conveyed closed-form analytical solutions of the system. In these methods, the conformal method is the best to calculate the seepage quantity by using numerical and analytical methods. Lakshmi N. Reddi described in his book the designing of filters and drainage layers, to easily let water dissipate, to reduce excess pore water pressure, and to avoid soil erosion. The book also gives an idea of designing seepage barriers or separators, pavement drainage designs, and dewatering systems. Seepage forces are also calculated with the help of a parameter called hydraulic gradient.

Geosynthetics material used in earth dams reduced the chances of seepage resulting in increasing the stability of the dams. It is now widely used, especially in rock-fill dams. It is a very promising and up-to-date material for the construction of dams.

Context and Applications

Seepage analysis and its principles are the subdivisions of soil mechanics and hydrology in civil engineering, and also a subdiscipline of agricultural courses. Its applications are widely used in all kinds of construction, architecture, and even soil management. It is an important subject in various courses such as:

• Bachelors in Technology (Civil Engineering)
• Masters in Technology (Civil Engineering)
• Masters in Technology (Geotechnical Engineering)

Practice Problems

1. Who among the following studies soil management?

1. Hydrologists
2. Agronomists
3. Biologists
4. Geologists

Correct option- b

Explanation: The person who studies the science of soil management is called an agronomist. A hydrologist studies water on the earth's surface, geologists study the geography of the earth, and a biologist studies life on earth.

2. Which of the following is the method for calculating seepage quantity?

1. Conformal mapping
2. Two-dimensional SPH analysis
3. Seepage separators
4. Geosynthetics method.

Correct option- a

Explanation: Conformal mapping is used to calculate the exact amount of seepage present beneath a hydraulic structure.

3. Who wrote the book "principles of seepage"?

1. RS Sandhu
2. LF Harza
3. Lakshmi N. Reddi
4. HR Cedergren

Correct option- c

Explanation: The book "principles of seepage" of soil mechanics was written by Lakshmi N. Reddi and John Wiley published in Hardcover.

4. Which of the following material is used to protect dams from groundwater seepage?

1. Bituminous
2. Concrete
3. Fly ash
4. Geosynthetics

Correct option- d

Explanation: Geosynthetics is used for the treatment and protection of dams from groundwater seepage.

5. What condition takes place when seepage pressure is equal to effective stress?

1. Saturation
2. Unsaturation
3. Vadose
4. Quicksand

Correct option- d

Explanation: When seepage and soil pressure become equal, effective stress becomes 0 resulting in quicksand conditions.

Related Concepts

• Soil mechanics
• Seepage treatment
• Geosynthetics