Pressuremeter testing is an in-situ test method used to develop stress-strain properties of soils and soft rocks. The most common and useful properties obtained from the testing are the Deformation Modulus, (E), and Limit Pressure (PL). These properties give geotechnical and structural engineers a more representative characterization of a given soil or rock profile, and allows more informed decisions with respect to the:
· Bearing capacity of shallow and deep foundations;
· Lateral deformation of deep foundations; and
· Settlement predictions of foundation elements.
Pressuremeter testing consists of placing a cylindrical probe in a soil or soft rock strata of interest, typically within a predrilled borehole, and pressurizing the flexible outer membrane of the probe radially against the soil or soft rock. The pressure applied and the relative increase in cavity radius are recorded, up to 40 data points per test, and an in-situ stress-strain curve of the material is developed. The Pressuremeter test can then be repeated at various depths to characterize entire profiles of soil or soft rock.
Borehole preparation is the most critical aspect of quality pressuremeter data. Click here for borehole prep guidelines and advice.
Pressuremeter test data. Pressure (stress) vs. radial strain.
While Pressuremeter testing is often used to supplement conventional testing and sampling, it is particularly beneficial in testing soil and rock formations in which standard sampling and testing procedures are marginally effective at best. For example, the Pressuremeter is the ideal method for obtaining data in soils or soft rocks that are too stiff to use push technology (Shelby tube samples, cone penetration testing, or dilatometer testing) but too soft or friable to obtain useable rock core samples.
In addition to the advantages of testing in difficult materials, Pressuremeter testing often permits the use of higher design bearing pressures than could have been considered by analysis of data obtained from conventional testing and sampling methods.
Pressuremeter testing, Colorado Springs, Colorado
Pressuremeter membrane calibration