Methods Of Soil Exploration Pdf

The effect of actual load on the building of the soil extends up-to the soft soil which is highly compressible and there will be failure. This method of boring is not suitable for very hard or cemented soils, very soft soils, casio manual pdf as then the flow into the hole can occur.

Therefore it is used extensively in detailed and special foundation exploration for important structures. Even after soil investigation, we are never sure about the samples collected and truly representative or not and so there is every possibility of misjudgement of sub-soil condition.

This may lead to disaster. Trial pits can be used for all types of soils.

It can conveniently be used in sands and silts also. The depth of various strata can be detected by inspection of cuttings. As far as possible the boreholes should be drilled closed to the proposed foundations but outside their outlines. Therefore the observed N-value is to be corrected. These provide both disturbed as well as undisturbed samples depending upon the method of boring.

Methods of soil exploration pdf

The boring methods are used for exploration at greater depths where direct methods fail. It provides more reliable and detail information on soil condition than the other methods.

Block samples are hand cut samples and are obtained from clay soil. The main aim of preliminary exploratory is to get an approximate idea of the sub soil at low cost, Few numbers of bore holes, test pits and penetration tests are carried out for general exploration. Trial pits are suitable for exploration of shallow depth only.

Both disturbed and undisturbed sample can be conveniently taken. While at site the sampling tubes are protected from direct sunshine, shock etc. It is slower method and more expensive than intermittent sampling.

Soil Exploration Purpose Planning Investigation and Tests

For such strata, percussion drilling is usually adopted. In irregular groundwater condition, hydraulic piezometer is installed for measurement of groundwater level. It requires fairly continuous sampling in stiff and dense soil, either to protect the sampler from damage or to avoid objectionably heavy construction pit.

The extent of exploration depends on the importance of the structure, the complexity of the soil conditions and the budget available for exploration. The drill rod is connected to the top of the split spoon sampler. Piezoncone penetrometer gives simultaneous measurement of cone resistance, side friction and the pore water pressure as the cone is advanced in the soil. These samples are required for identification and classification tests. In this method the driving energy is supplied by the fail of the drop weight.

Methods of soil exploration pdfMethods of soil exploration pdf

Auger Boring Augers This method is fast and economical, using simple, light, flexible and inexpensive instruments for large to small holes. We do not have the idea of soil condition in between the boreholes and must rely in interpolation combined with knowledge of soil deposition processes. Here, the bore holes are advanced in depth by rotary percussion method which is similar to wash boring technique.

Addition of sand increases the cutting action of the drilling bit in clays. Casing or drilling mud may have to be used where the boring sides fall in. The details of field test results are presented in this section of the soil report. This type of work is adequate for small structures and is useful in the preliminary exploration for extensive sites. The best modern practice still adheres to this dimension.

Samples obtained are disturbed samples. The pressure required for pushing is recorded as q c. It is a fast and simple method for advancing holes in soils. Drilling equipment should be for making a reasonably clear hole of mm diameter so as to ensure that the test is performed in undisturbed soil and not in the fall in material.


Methods of soil exploration pdf

The bit is attached to the end of a drilling rod and is raised and dropped alternately in the bore hole. This method is also not suitable for fully saturated cohesionless soil. The sampling operation advances the borehole and the boring is accomplished entirely by taking samples continuously. Just by noting the change of colour of soil coming out with the change of soil character can be identified by any experienced person.

This number of blows is called N-value or penetration number. No consideration is made for entrapped water under the clay layer.


This represents the amount of soil that is displaced when a sampler is forced into the ground. It involves the preliminary feasibility study that is undertaken before any detailed planning is done. During lowering of sampler in the hole, the piston is kept closer to the lower end of the sampler. It gives completely disturbed sample and is not suitable for very soft soil, fine to medium grained cohesionless soil and in cemented soil.

Soil Exploration Purpose Planning Investigation and Tests

If a geotechnical engineer fails to detect the limestone rock underlying the cohesive soil and construction is done over it. To obtain the most useful information at minimum cost and effort, proper planning of subsurface investigation programme is essential. The particle size distribution of in-situ soil is preserved. The top layer is stiff clay and bottom layer is soft clay. This method is fast and economical, using simple, light, flexible and inexpensive instruments for large to small holes.

In wash boring the hole is advanced to a short depth by auger and then a casing pipe is driven in the ground to prevent the sides of the bore hole from caving in. Therefore not suitable for loose sand. Bearing Capacity of Soil With Diagram. The sample is then covered with lid and is sealed with wax or grease. No sample is obtained from this test.

Methods of soil exploration pdf