Man can be affected in a multypilicity of ways by insects. Insects can attack his body, his food, crops, fruits, other aggricultural products including his stored possesssions and even the house in which he lives.
Insecets could be defined as ancient race of animals which have been in existance for million of years. They are capable of survival under most adverse conditions and environments.the type of insects known as termites cause maximum damage to the buildings. Termites are divided mainly into following two types:
1. Dry wood termites
2. Subterranean termites
1. Dry wood termites
They live in wood and do not maintain contact with the ground. They normally build nests within the dry timber members like door window frames, wooden furniture etc. and destroy them gradually.
2. Subterranean termites
They on the other hand are mainly responsible for causing damage to the buildings and it cantents. Unlikely dry-wood termites they live in soil and require moisture for their existance. They build underground nests or colonies and form mud-wall tunnels or runways(tube) which serve as protected shelter for their movements. Sometimes they build nests near ground in stumps of dead trees or creat colonies in the form of dome shaped mounds on the ground. It is through these mud wall tubes that they maintain direct conctact with the soil for meeting their moisture requirements and conditions of darkness essentially needed for their survival. The termites enter the building through foundations or from adjacent to buildings and advance upward through floors destroying everything that comes eithin their reach.
Treatment
Pre-constructional Measures
1.For load bearing walls
For load bearing walls, treatments of soil shall be carried out at the bottom of the trenches and at the sides up to 300 mm above the bottom(fig-1 and fig-2). In such cases, 5 litre of the chemical shall be sprayed per sqr. M of the surface area. The backfill material in direct contact with the foundation shall be treated with 15 litre of chemical emulsion per sqr. m of the surface area of the foundation. If water is used for compaction operation, it shall be done applying the chemicals. Treatment shall follow the same layer wise sequence as that of the backfilling operation.
2. For frame structure
For frame structures, if the concrete mix of the foundation is 1:2:4 or richer, treatment of soil at the bottom of the trench is not needed. A layer of soil at a depth of 500 mm from the ground level shall be prepared. Details of the treatment is shown in fig-3. The density of the chemicals in such treatment shall be 15 litre per aqr.m.
The top surface of the plinth in any building having a floor at the ground level shall be treated with a chemical emulsion at the rate of 5 litre per sqr. m.
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