In situ testing
In situ stress measurements
In situ testing
Measurements and monitoring
Test depth over 1000 m, borehole with any orientation (also upward). The probe is handled with cable + winch or with battery of drilling rods.
Soils and Weak Rocks => flexible sleeve dilatometers (borehole diameter 76 – 101 mm)
A radial pressure is applied to the borehole wall, increasing it with a regular speed and measuring the values of the corresponding variation of diameter of the hole at fixed time intervals. In weak rocks and soils, the pressure can arrive to breakage of the wall of the hole. In this case, in addition to the characteristics of elastic deformability, the interpretation of the test can provide the strength characteristics of the rock. The probe consists of a steel body covered with a reinforced rubber sleeve. The pressure inside the sheath is applied by gas (technical nitrogen). The variations in diameter are measured by means of three potentiometric displacement transducers, arranged in three directions at 120 ° in the median zone of the dilatometer. The pressure inside the dilatometer and the signals of the displacement transducers are transmitted by means of an electrical cable to a datalogger.
Concrete and Rock => Goodman Jack (bore diameter 76 – 96 mm)
The Goodman Jack applies a diametrical load to the walls of the hole, measuring the corresponding variation in diameter. In this way it is possible to determine the deformability modulus of the material under test. The pressure is applied by means of mobile steel plates moved by 3 hydraulic pistons, which allow to reach a pressure of 70 MPa; since the hydraulic efficiency of the tool is equal to 0.55, it follows that the maximum pressure applicable to the walls of the hole is 39 MPa. To measure the displacements, 2 LVDT transducers are used, located at the ends of the plates. The load plates are 204mm long and have an external bend radius of 38.1mm. The central angle subtended by each plate is 90 °. The Goodman Jack test, performed in a hole of known diameter D, provides a curve of the applied pressure ΔQ as a function of the diametrical variation ΔD.