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Types, Concept & Theory
By: Haseeb Jamal
Lateral Earth Pressure
In 1929 Terzaghi (The Father of Soil
Mechanics) conducted experiments on the retaining wall and showed the relation
of pressure on the wall if wall changes its position i.e. to move inwards to
the backfill, outwards of it or remain at its place.
There are three types of earth pressures on
the basis of the movement of the wall.
1.Earth Pressure at
rest
2.Active Earth Pressure
3.Passive Earth
Pressure
These are explained below
Pressure at rest:
When the wall is at rest and the material is in
its natural state then the pressure applied by material is known as Earth
Pressure at Rest.
It is represented by P0.
Active earth pressure:
When the wall moves away from the backfill,
there is a decrease in the pressure on the wall and this decrease continues
until a minimum value has reached after which there is no reduction in the
pressure and the value will become constant.
This kind of pressure is known as active
earth pressure.
Passive earth pressure:
When the wall moves towards the back fill,
there is an increase in the pressure on the wall and this increase continues
until a maximum value has reached after which there is no increase in the
pressure and the value will become constant.
This kind of pressure is known as passive
earth pressure.
This means that when the wall is about to
slip due to lateral thrust from the backfill, a resistive force is applied by
the soil in front of the wall.
Coefficients of earth pressure - Earth
Pressure Coefficient
On a small unit at depth Z in the back there
are two kinds of pressure.
1. Vertical Earth
pressure:
The pressure applied in the vertical
direction due to the back fill lying above it.
2. Horizontal Earth
pressure:
The pressure applied in the horizontal
direction due to backfill is called the horizontal pressure or lateral earth
pressure
Coefficient of active earth pressure at rest:
When the retaining wall is at rest then the
ratio between the lateral earth pressure and the vertical pressure is called
the co-efficient of the earth pressure at rest,
Ko = lateral pressure / vertical pressure
Co-efficient of active earth pressure:
When the retaining wall is moving away from
the backfill the ratio between lateral earth pressure and vertical earth
pressure is called coefficient of active earth pressure.
Ka = lateral pressure / vertical pressure
Coefficient of passive earth pressure:
When the retaining wall is moving towards the
backfill, then the ratio between the lateral earth pressure and the vertical
earth pressure is called the coefficient of passive earth pressure.
Ka = lateral pressure / vertical pressure
I am a Civil Engineer, graduated
from University of Engineering and Technology, Peshawar, Pakistan in
2010. I also have a PG-Diploma in Disaster
Management and MS in Urban Infrastructure Engineering (In
Progress). My expertise include civil related softwares like AutoCAD,
SAP2000, MS Project, Primavera, MS Office and GIS. My technical skills include
project management, monitoring and evaluation, structural assessment, disaster risk
management, Quantity survey, land survey, material testing, site management and
technical writing. I am trained in writing project progress reports as well as
proposals and concept papers. I have also received advanced training on
surveying, proposal writing, Monitoring and Evaluation of projects as well as
organizations.
I have worked as Project
Engineer at National Research and Development Foundation, Peshawar and
CENCON Associates. I also worked with Spectra Engineering Solutions as Senior
Civil Engineer in monitoring of World Bank and UNDP funded projects
all over Khyber Pakhtunkhwa and FATA. Currently, I am working as Deputy
Manager Development at NayaTel, Peshawar.
https://www.aboutcivil.org/earth-pressure.html
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