Following factors are responsible for the disturbance of sample: Wash samples collected from rotary and percussion drilling method for rock masses are also highly disturbed, but rocks samples collected as blocks or cores are undisturbed. Soil samples collected by wash boring and auger boring method subjected to high disturbance. Some disturbance is unavoidable during sampling, even though utmost care in total process is adopted. No change in chemical properties of constituents.Water content and void ratio must be unchanged.Soil structure should be unaltered due to disturbance.In this regard, undisturbed sample collected by different laboratories may have wide variations. Undisturbed samples of most rock can easily be obtained but it is almost impossible to collect an appropriate undisturbed and when the term undisturbed is used, it refers to a sample that are collected with some precautions to reduce disturbance of soil skeleton that exist before boring or sampling. Undisturbed samples of cohesive soils can be collected with relatively less difficulty and fairly accurate evaluation of these properties can be obtained by laboratory tests. The engineering properties of soil that are most important for design of foundation are strength, permeability and compressibility. The small the disturbance, the more reliability of results. If all condition meets during collection of samples from bore hole, during removal of this sample produces change in stress as conditions and get disturbed.

It is a theoretical term as some disturbance is unavoidable. The samples that retains its natural water content and structure of soil are known as undisturbed samples. The index properties like specific gravity, grain size and plasticity characteristics can be determined from such sample.Undisturbed sample The only information that can be determined form this sample are mineral content and composition of soil. The samples that are lost their natural structure during collection process are called disturbed sample.

Disturbed undisturbed soil samples