Radial Displacement Mean?
Radial displacement is a component of change in the radial direction or displacement along the radius of the borehole. Sub-surface soil and rock formations are constantly under stress due to overburden pressure and tectonic stresses. During installation of pipelines using trenchless construction methods such as horizontal directional drilling (HDD) and microtunneling, boreholes are drilled under the earth's surface.
Inadequate drilling fluid or overcoring of borehole can cause stresses to develop in the borehole leading to instability or collapse.
Trenchlesspedia Explains Radial Displacement
Radial displacement in boreholes can be measured by using instruments known as deformation cells. Overcoring is a preferred technique and utilizes six cells. The radial displacement is measured and converted to stress magnitudes along with other properties such as Young's modulus and Poisson's ratio derived from cored samples. Overcoring is done in a pilot hole fitted with a strain gauge, beginning at the borehole diameter.
Radial displacement is recorded by the strain gauge and used for estimating stress for various geological conditions.