Tilt test (geotechnical engineering)
Encyclopedia
In geomechanics a tilt test is a simple test to estimate the shear strength parameters of a discontinuity
. Two pieces of rock containing a discontinuity
are held in hand or mounted in test equipment with the discontinuity
horizontal. The sample is slowly tilted until the top block moves. The angle with the horizontal at onset of movement is the so-called tilt-angle.
The size of the specimen is limited to 10-20 cm for hand-held tests, while machine-operated tilt test equipment may handle up to meter-sized samples. In the field, the angle can be determined most easily with an inclinometer
as present in most geological or structural compasses
.
wall plus the roughness i-angle (tilt-angle = φwall material + i) if no real cohesion is present (i.e. no cementing or gluing material between the two blocks), no infill material is present, the asperities
do not break, and the walls of the discontinuity
are completely fitting at the start of the test, while if the walls of the discontinuity are completely non-fitting, the tilt-angle equals the friction of the material of the discontinuity
walls (tilt-angle = φwall material). If cementation or gluing material is present or asperities
break, the tilt-angle represents a combination of the (apparent or real) cohesion and the friction along the discontinuity. If infill material is present, the tilt-angle is governed partially or completely by the infill, depending on the thickness of the infill and height of asperities
.
Direct shear test
Discontinuity (Geotechnical engineering)
Shear strength (Discontinuity)
Triaxial test
Discontinuity (geotechnical engineering)
A discontinuity in geotechnical engineering is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane...
. Two pieces of rock containing a discontinuity
Discontinuity (geotechnical engineering)
A discontinuity in geotechnical engineering is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane...
are held in hand or mounted in test equipment with the discontinuity
Discontinuity (geotechnical engineering)
A discontinuity in geotechnical engineering is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane...
horizontal. The sample is slowly tilted until the top block moves. The angle with the horizontal at onset of movement is the so-called tilt-angle.
The size of the specimen is limited to 10-20 cm for hand-held tests, while machine-operated tilt test equipment may handle up to meter-sized samples. In the field, the angle can be determined most easily with an inclinometer
Inclinometer
An inclinometer or clinometer is an instrument for measuring angles of slope , elevation or depression of an object with respect to gravity...
as present in most geological or structural compasses
Compass
A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...
.
Tilt-angle
The tilt-angle equals the material friction of the discontinuityDiscontinuity (geotechnical engineering)
A discontinuity in geotechnical engineering is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane...
wall plus the roughness i-angle (tilt-angle = φwall material + i) if no real cohesion is present (i.e. no cementing or gluing material between the two blocks), no infill material is present, the asperities
Asperity (geotechnical engineering)
In Geotechnical engineering the term asperity is mostly used for unevenness of the surface of a discontinuity, grain, or particle with heights in the range from approximately 0.1 mm to many decimetre...
do not break, and the walls of the discontinuity
Discontinuity (geotechnical engineering)
A discontinuity in geotechnical engineering is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane...
are completely fitting at the start of the test, while if the walls of the discontinuity are completely non-fitting, the tilt-angle equals the friction of the material of the discontinuity
Discontinuity (geotechnical engineering)
A discontinuity in geotechnical engineering is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane...
walls (tilt-angle = φwall material). If cementation or gluing material is present or asperities
Asperity (geotechnical engineering)
In Geotechnical engineering the term asperity is mostly used for unevenness of the surface of a discontinuity, grain, or particle with heights in the range from approximately 0.1 mm to many decimetre...
break, the tilt-angle represents a combination of the (apparent or real) cohesion and the friction along the discontinuity. If infill material is present, the tilt-angle is governed partially or completely by the infill, depending on the thickness of the infill and height of asperities
Asperity (geotechnical engineering)
In Geotechnical engineering the term asperity is mostly used for unevenness of the surface of a discontinuity, grain, or particle with heights in the range from approximately 0.1 mm to many decimetre...
.
See also
Asperity (Geotechnical engineering)Asperity (geotechnical engineering)
In Geotechnical engineering the term asperity is mostly used for unevenness of the surface of a discontinuity, grain, or particle with heights in the range from approximately 0.1 mm to many decimetre...
Direct shear test
Direct Shear Test
A direct shear test also known as shearbox test is a laboratory or field test used by geotechnical engineers to measure the shear strength properties of soil or rock material, or of discontinuties in soil or rock masses.- Soil :...
Discontinuity (Geotechnical engineering)
Discontinuity (geotechnical engineering)
A discontinuity in geotechnical engineering is a plane or surface that marks a change in physical or chemical characteristics in a soil or rock mass. A discontinuity can be, for example, a bedding, schistosity, foliation, joint, cleavage, fracture, fissure, crack, or fault plane...
Shear strength (Discontinuity)
Shear strength (discontinuity)
The shear strength of a discontinuity in a soil or rock mass may have a strong impact on the mechanical behavior of a soil or rock mass. The shear strength of a discontinuity is often considerably lower than the shear strength of the blocks of intact material in between the discontinuities, and...
Triaxial test