Materials and construction of soil
Rocks and soil form the prime structural components and deep knowledge is required for maintaining safety and economy in foundation design & construction.
The site inspection plays an important role for developing the building securely.
The site inspection is performed for the following purposes :-
- To determine the nature, thickness and difference in the soil strata in the region.
- To evaluate the physical characteristics of the soil strata. It facilitates finding out the design and mode of construction of the foundation.
- To examine the difference and the impact of ground water table on the soil strata.
- To determine the values of strength and compressibility of soil bed.
- To determine the depth of fundamental rock, soil bed.
The following initial inspections should be undertaken for the soil inspection :-
- It comprises of the examination of the topography of the site.
- Provides information concerning the soil & the conditions of ground water.
- Aerial reconnaissance is performed for a major location.
- This activity provides the primary conception of the soil in the site.
Study of maps
- Geological inspection of the site is necessary to determine the seismic reactions.
- Maps are also suitable to determine the existence of ground water table in that specific area.
- These photographs are taken by flying more or less straight lines above the site & mapping. For traditional mapping the scale of 1:20,000 is used.
Methods of soil exploration
The following methods are used for this purpose :-
- Direct Methods
- Indirect Methods
- Semi Direct Methods
Open Test Pits (or) Trial Pits :-
- These belong to the open type of available explanatory methods :-
- These are utilized for examining the stability of the soil and suitable for different types of soil.
- It is also ideal for field test like plate load test (to detect the safe bearing strength of the soil).
- Since the cost is raised with depth, it is restricted only for depth of 3 metres.
- For deeper depths, for penetrable soil, lateral supports or bracing should be provided and it delays the process as well as exorbitant.
- Usually, for deeper depths, bore holes are applied.
- Also at deeper depths, the ground water table may also interrupt the process and it should be reduced. More expenditure is incurred for that.
Sub - Surface Soundings
- This method is applied for examination of the strata with different soil nature.
- It is applied to find out the consistency of cohesive soils and density index of cohesion free soils at several depths.
- The gadget applied for this is known as penetrometers.
- The field test done for this purpose is defined as penetration test.