Considerations for the construction of houses in mining zones

[edit] Introduction

Mining is among the major economic sectors in many of the countries in the world. Developing countries have a long history of mining, and currently they are growing fast. There have been claims from the community, that the homes have been damaged due to mining operations.

Mining works produce noises, vibrations and dust:

• NOISES are developed due to heavy moving machines and trucks that are being used for earthmoving, haulage of materials and crushing of stones.
• VIBRATIONS are developed from blasting that is necessary for deepening the pits and for mining the ore and wastes rocks.
• DUSTS are caused by the blasting sites, moving trucks on earth or gravel roads and also from the crushing (Quarry) plants.

Designing a residential, commercial, school or any other public or private facility in mining zones requires an understanding of certain technical issues that will ease the stresses imposed on these structures.

[edit] Foundations

When deciding on the type of foundation to be used, the key factor is the geological structure of the ground beneath (level of water table, soil type, permeability of soil, Bearing capacity and the compressibility of the soil).

In mining areas raft/ mat foundations are preferred; as they form a continuous slab structure that carries the whole imposed and self weight of the structure to the underlying subsoil. Whether there are vibrations due to blasting or settlement stresses developed by the compressibility of the brought up soil from mining, raft foundation can be structurally stable enough to withstand loads and the stresses imposed.

For, small structures such as detached houses, or single storey structures, a deep strip foundation combined with pads positioned at the corners of the building can be sufficient to bear structural loads.

[edit] Walling

Walling can be designed in a such a way that noises from outside are not allowed to penetrate inside. For a brick wall it is structurally viable to erect a 230mm thick brick wall jointed with 10-15mm thick, 1:4-1:6 cement sand mortar.

For, block wall; blocks should be tested and checked for compression strength and abrasion resistance. Compression strength should at least be 7.5N/mm². Built with 150mm thick or greater block wall jointed with mortar of 1:4-1:6 cement sand mortar.

For all of the above, there should be wall ties placed alternately along the height of the wall or placing 2, 6mm-12mm diameter bars laid on the bed of the mortar and placed alternately at after every 3 courses of bricks or blocks. These will help to take all the stresses applied reducing damage such as cracks or wall splitting that could have occurred in their absence.

When dry walls are erected such as stud walls, careful analysis should be undertaken before commencing any works; intensity of vibrations (tremors) and the frequency of blasting whether it is weekly or monthly. The analysis will help to make design decisions about what type of timber to be used, spacing of studs and mullions; mostly 2’’x6’’ wrot hard wood timber are used for studs, mullions and base plates; placing studs at 2’ center to center would be considered economical and structurally sound. Also special approved nails should be used to fix up the board on the 1’’x1’’ wrot soft wood brandering frame.

[edit] Roofing

The roofing form adopted should be strong enough to withstand the common stresses and the regular stresses from the mining works.

Roofing form should be of low pitch, As high pitched roofs have high center of mass and hence it easy for it to fall when the vibrations are applied unto it; Roof construction should be made of wrot treated soft wood. Members to be fixed are Rafters 2’’x6’’, struts 2’’x4’’, tie beam 2’’x6’’ or replaced by double 2’’x4’’ tie beam, wall plate 2’’ x 4’’. The Roof Trusses should be closely spaced at not greater than 3’ center to center.

[edit] Landscape

Due to dust in mining zones, landscape layout plans should help to prevent the dust from entering the houses. A landscape that, on the front of the house is covered with tall high leafed trees will help to trap dusts and reflect noises coming towards the house.

Written by; Nyondwi, Yoktani.

Professional Engineering Technician

Email: [email protected]