GEOMETRICAL & GENETICAL

CLASSIFICATION OF JOINTS

ByA-Team

T.Venkatesh,Ananth,Varsha,Kiruthika.

Joints may be defined as cracks or fractures present in the body of a rock.

These joints thus divide the rock into parts or blocks.

The joints may be either open or closed.

INTRODUCTION

Open joints – In which the rocks are separated or opened out for some small widths in a direction at a right angle to the fracture surface.

Closed joints – However there is no such separation.

CONTINUE…

Major Joints – In this prominent and well developed and extending continuously for considerable lengths as compared to others.

Such major joints are called as master joints or prominent joints.

CONTINUE…

The inclination of the joint plane with the horizontal is called dip of the joint.

The line along which the joint plane meets the surface is called strike of the joint.

The strike direction is perpendicular to dip direction.

ATTITUDE OF JOINTS

The Joints may be classified into two major classifications.

1) Geometrical Classification

2) Genetic classification.

CLASSIFICATION OF JOINTS

The geometrical classification of joints is based on attitude the of joints with respect to that of the beds.

Accordingly there are three types of joints that is strike joints, dip joints, oblique joints & bedding joints.

1. GEOMETRICAL CLASSIFICATION

Strike joints are those in which the strike of the joint is parallel to the strike of the beds.

I . STRIKE JOINTS

Dip joints are those in which the strike of the joints is perpendicular to the strike of the beds .

ii. DIP JOINTS

Oblique joints are those in which the strike of the joints are neither parallel nor perpendicular to the strike of the joints.

iii. OBLIQUE JOINTS

They are parallel to the bedding plane having same plane having same strike & dip.

iv-BEDDING PLANE

Depending upon the causes of their origin, joints may be divided into

i. Tension joints ii. Shear jointsiii.Compression joints

2. GENETIC CLASSIFICATION

Tension joints are those which are formed due to tension forces or stresses produce in the rock.

The direction of the joints is always perpendicular to that of the force which tries to pull them apart.

i. TENSION JOINTS

They are formed by the shearing stresses , which tend to slide one part of the rock against other.

They are developed during folding & faulting.

These joints are developed in the limbs of the folds.

ii . SHEAR JOINT

Rocks may be compressed to crushing & numerous joints may result due to compressive forces in this case.

In the core regions of folds where compressive forces are dominant results in the compression joint.

Iii . COMPRESSION JOINT

For civil projects the investigation of rock joints is important because joints acts as source of weakness for the rocks, and also as a source of leakage through the rocks.

The joints play a vital role in landslides in hilly regions, because they serve as a slip surface.

SIGNIFICANCE OF JOINTS

Physical and engineering geology – S.K. Garg,

Engineering and general geology – Parbin Singh.

REFERENCE:

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