The document discusses excavation and foundation work procedures, including requirements for starting excavation. It notes that excavation is needed to lay foundations, plumbing, and more. Before excavating, a trial pit per 400 sqm of plot area must be dug to determine the soil strata, which can include black cotton soil, red soil, silt, sand, gravel, murum, and rock. The bearing capacity of the foundation depends on the soil strata and must be tested using static penetration or plate bearing tests. Different soils are described and have varying approximate safe bearing capacities.

1. EXCAVATION AND FOUNDATION WORK
PROCEDURE - TEST, SAFETY, DEWATERING
What is excavation of foundation trench ?
"EXCAVATION" is the preliminary activity of
the construction project It starts from digging pits for the
building foundations and continues upto the handing over of the
project.
Excavation is needed for
 Foundations of building
 Plinth beam plinth masonry

2.  Basement of the building
 Under ground water tank
 Septic tank
 Laying drainage, water lines, electric cables etc.
 Foundation of compound wall
 Footings of main gate
 Earthing pit, etc.
REQUIREMENTS TO START EXCAVATION
(1) STUDY OF STRATA TRIAL PIT
The stability and design of the building depends on the strata on
which it rests. So, a trial pit per 400 sq.m. area of the plot should
be made, to know the strata pattern.
Trial pit should be size 1.2 m x 1.2 m. The depth depends upon
the strata that will be unearthed.
Generally, during excavation the different layers of soil are
found, as shown in Fig, No. 21.1, The depth of the respective
layers may vary from location to location.
(1) Black cotton soil
(2) Red Soil
(3) Silt, sand and gravel
(4) Shadu soil
(5) Soft murum
(6) Hard murum

3. (7) Soft rock
(8) Hard rock
Generally, the size of the footing depends on the bearing
capacity of the strata. The following table shows various soils
and their respective approximate bearing capacities.
APPROXIMATE MAXIMUM SAFE
BEARING CAPACITY OF VARIOUS SOILS
NOTE : The bearing capacities given in table No. 21.1 are
approximate and given on the basis of average strata, Actual
bearing capacities of the strata should be derived by.

4. 1. Static penetration test (SPT) - For soil and clay
2. Plate bearing test - For murum, rock.
During the execution of the work, the actual bearing capacities
of the strata should be checked at site and approval for the same
be secured from the Structural Consultant.
(2) TESTING OF SOIL PRACTICAL NORMS
AND LABORATORY TESTING
During excavation, it is necessary to study soil samples for
finalizing the bearing capacity. Given below area few
observations for different strata.

5. BLACK COTTON SOIL
 Greyish black in colour
 Heavy clay contents of unreliable quality
 Swells when wet and shrinks when dry
 Wide cracks develop when dry
 Termed as poor soil for foundations
RED EARTH
 Red in colour
 Absorbent in nature
 When dry, turns to clay
 Forms hard lumps, not easily breakable
 Lump cannot be powdered by hand
SHADU
 Yellowish/whitish brown in colour
 Intermediate stage between clay and sand
 Sand particles can be felt when rubbed
 Contains moisture when wet and possesses appreciable
cohesion when dry.
 Termed as reasonably good soil for foundations

6. MURUM
 Red, brown in colour
 Found in lumps/layers when excavated
 Lump is of irregular thickness, size and shape
 Well compacted deposits when dry
 Can be broken, if forced by both hands
ROCK
 Generally found as the lower most layer
 May be black, red or of any colour
 Very strong, cannot be excavated with pick aхE
 Termed as very strong strata for foundations
BEARING CAPACITY OF SOIL
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