Soil Investigation

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by elin283
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Soil Investigation

(a) corrosion - problem of soil corrosion is extremly complex. 1 of the more common types of corrosion is the deterioration of concrete owing to the presence of soluble sulphate salts in the soils. the problem is acute in semi-acis climate where there's insufficient rainfall to carry away soluble salts. if such salts present, concreate structure may be protected by the use of sulphate resistant cement.(b) swelling - highly plastics soils have the ability to swell depend upon the clay minerals presents & the initial water content of the clay. test on swelling soils cannot give definiate design criteria, but they serve to point up the potential seriousness of the problem & indicate methods of overcoming it.(c) permeability - because soil is a porous system, water will move through it under hydraulic gradient. permeability may be defined as the ability of a soil to pass water. the choice of the test method will depend on the porosity/permeability of the soil. knowledge of the permeability of soils is a vital factor in the design of earth dams & dykes is important also in the design of drainage system.

- to ensure that the earth material meets the required spesifications- there is unique relationship between water content & soil densityto ensure the densities are achived field density test are conducted on the site, the choice of method being dictated by the type of soil involved

control test

-repeated blows breaking up the ground formation to sink the boreholes.- water added to boreholes as the work proceed & the soils removed at internal

- this method is removing loosed soil from a bore hole using a strong jet of water or bentoite which is controlled mixture of fullers earth & water.- this jet sunk disintegrate & dispalce the soil & returns the disturbed soil the way of returning water.- this method has their advantages of produsing subsoil sample which has not been disturbed by impact of sampling sheels.- not suitable for large gravel/subsoils which contain boulders

aim of SI1. tp evaluate suitab;e site fpr poject2. to create safe and economical design3. to exercise safety & investigate case of failure4. to identify main problem during the construction(a) soil problems(b) determine precautionary action

soil investigation

1. to determine information related to soil in various & depth2. to find ground water level3. determine chemical & physical properties.


1. soil test be conducted on samplesthat are truly reprentive of the soil at the site2. proper soil testing has proved to be a reliable basis for the design foundations & other structure3. to describe engineering soils, test commonly used in site investigations= & to indicate their potential used= and limitations.

post holes/hand auger holes

1. field test(a) trial pitssuitable for dry condition. excavating a hole large enough for a person to work in & revealling the soil strata for examining and sampling. shallow investigation up to 3m although sometimes sheetin & battering neecd to ensure stability.(b)boringscheap method of subsurface exploration for soil. holes can be sunk about 3m no obstruction such as boulders. dia boreholes about 150mm-200mm. used in non cohesive involve using of casing to prevent collapse of the boring. the types is post hole auger, shell and auger, precussion and wash boring.2. lab test(a) classifications / indiacators test- cohesionless soils(sand)- cohesive soils(b) strength - density test(c) control test(d) special test- corrosion testswelling - permeability

soil investigation method

using a simple hand operate tool. depth up to 3m in soft ground (gravels/loose sand. the advantages using this is generally cheaper & simpler method of obtaining subsoil samples than the trial pits.

shell & auger boring

- operated in soft ground up to a depth of 20mm- greater depth a mechanical tools used- casing needed are positioned by means of a "monkey" suspended from the winch.

wash borings


rotary boring- can be used for rock investigation & core samples can be obtained using coring tools(a) core drilling - produced a continues core of rock(b) mud rotary drilling - drilling action w roatary bit(c) shot drilling - head consists of chilled steel shot.core drilling ----> water or compressed air is jetted down the bore hole through a hallow tube & returns via the annular space. coring tools extract continuos core of rock samples are sent in wooden boxer for lab rotary testing.

strength-density test- cohesive soils mobilize their strength in direct proporotion to the loads applied.- greater the density of a soil, the more internal friction can be mobilized.- most common method of assessing density is a penetration test.

special test

field test/in-situ test(a) standard penetration test - test measure the resistance of a soil to the penetration of a split spoon/split barrel sampler driven into the bottom borehole. soil to depth 150mm by a falling through a distance 760mm. the sampler is then driven into the soil a further 300mm & the number of blows counted up to a max of 50 blows. this test establised the relatives density of the soil.(b) vane test- measure the shear strength of soft cohesive soil. the steel vane is puhed into the soft clay soil and rotated by hand at a constant rate.

soil samples has 2 (1) disturbed soil samples (2) undisturbed soil samples


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