Among all of material used for construction, soil stand as one of the most interesting yet complex material to study by testing via field or laboratory. The common knowledge of us as the Earth dwellers is that we are living on its surface and it is a must for understanding the 30% ground mass of our world. In engineering especially at construction site, almost all the man-made structures supported and in direct contact with our ground.
Soil has been the oldest construction material used by humankind, and is also the most plentiful. The youngest discipline of civil engineering, soil mechanics covers the investigation, description, classification, testing and analysis of soils to determine its inter-relation with structures built in or upon it, or built with it.
Soil in Site Investigation
Purposes of Soil Testing
The physical properties of soils are usually determined by carrying out tests on samples of soil in the laboratory, obtained from the selected site or burrow pits. These tests shall be divided into two main categories:
- Firstly the classification tests, which will indicates the general type of soil and the engineering category to which it will belong.
- Secondly, tests for the assessment of engineering properties, such as shear strength, compressibility and permeability.
The parameters determined from laboratory tests, taken together with descriptive data related to the soil example through observation; which required by soil engineers for many reasons. The more usual applications are as follows:
- The acquired data from classification tests are applied to the identification of soil strata (profile) when the subsurface conditions of a site are being investigated through the process called site investigation.
- Other test data enable the soil engineering properties to be qualified in numerical terms, which can then be used as the basic of analysis on which the recommendations os the investigation report are based.
- Test data maybe used for the confirmation of assumptions which have been based on the previous experience and engineering judgments.
- The acceptance criteria of a soil used in construction can be drawn up in the light of available test results (most probably after the operation events).
- Laboratory tests are needed as part of the control measures which later be applied in construction of earthworks (cut and fill) or excavation works, especially for ensuring that the design criteria are met.
- The findings of site investigation can be supplemented by further testing as construction proceeds, as, for instance, when new ground is being opened up.
Advantages of Laboratory Testing
During the field operations known as site investigation as prime importance for any construction projects, where the studies of the geology and history of the site, subsurface exploration and in-situ testing. The determination of the ground characteristics by in-situ testing can be take into account of large-scale, such as soil fabric, structure and discontinuities of strata, which cannot be represented in small laboratory specimens. Nevertheless the measurement of soil properties by means of laboratory tests offers a number of advantages, as follows:
- Full control of the test conditions, including boundary conditions, can be exercised,
- Control cab be also exercised over the choice of material which is to be tested,
- Laboratory testing generally permits a greater degree of accuracy of measurements than doing it on field (at in-situ),
- A test can be conduct under conditions which are similar to, or which differ from, those prevailing in-situ, as maybe appropriate,
- Any changes in conditions can be stimulated, as it will most likely to occur during or after completion of construction,
- Tests can be carried out on soils which have been broken down and reconstituted, or processed in the other ways.
The Scope of Soil Laboratory Testing
The General Applications
During the past decades of evaluating the properties of soil from reliable test procedures has led to a closer understanding of the nature and probable behavior of soils as civil engineering number one materials. Some of the resulting benefits in the realm of civil engineering construction have been:
- Reduction of uncertainties in the analysis of foundations and earthworks,
- Economies in design due to the use of lower factors of safety,
- Exploitation of difficult and complex sites,
- Erection of structures and below ground level construction which would not have been feasible without this essential knowledge,
- Increased economy in the use of soils as construction materials, examples like in earth dams and embankment fills of roads, and so forth.
In soil testing, as in all laboratory work, it is necessary to take measurements of different kinds and to record it. Instruments used for making measurements of various kind are listed first. We will cover a lot more in another session of soil laboratory testing and until then take care…
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Author: Mr. Vine | Creator: Civil Craft Structures | Subscribe: RSS or Email
