Pressuremeter test

The ultimate bearing capacity, q it, for the soil zone supporting a shallow foundation, based on theoretical considerations with empirically determined modifications, has been related to the limit pressure as follows  

The settlement. A//, of a shallow foundation situated in homogeneous soil can be estimated from  

q es = foundation design bearing pressure minus the vertical pressure of the soil overburden adjacent to the foundation base Bo = a. reference dimension, equal to 0.6 m or 2 ft, B = width or diameter of the foundation, provided that B is equal to or greater than Bo or = rheological or creep deformation factor, which depends on the soil type and the ratio (Table 4.6) EJ Pi — g ) Ac, = shape factors that are based on length-to-width ratio of the foundation (Table 4.7)  

---

Methods of in situ measurement of strength. CPT, cone penetration test DMT, dilatometer test PMT, pressuremeter test SPT, standard penetration test VST, vane shear test. 

Beaufort Sea Clay -0.6 1.0 Jefferies et al. (1985) K as determined by pressuremeter ranged from 0.3 at surface to 2.0 at depth. K consolidated undrained triaxial tests (CKU) agreed well with CPT tests (N = 10). Very limited CKU tests. Pressuremeter tests compared very weU with UU tests... 

Hughes, J.M.O., and Robertson, P.K. 1985. Full-displacement pressuremeter testing in sand. Canadian Geotechnical Journal, 22 298-307. 

Field test are carried out in the excavated pits or boreholes at the required depths. The results reflect the mass characteristics of the ground as well as overcome disturbance effects of samples retrieved for laboratory tests. Common field tests carried out to assess strength, compressibility and seepage parameters are as presented in Table 3.5 (Canadian Geotechnical Society 1987). Typical equipment for pressuremeter test and test setup for plate bearing test are shown in Figures 3.6 and 3.7 respectively. 

For stiff clay, a careful load-unload and reload sequence is applied using small increments and decrements For soft clay, reliable determinations of the yield shell are made Estimates of settlement can be much improved if small strain triaxial and pressuremeter tests are used... 

Direct measurements on settlement and bearing capacity may be carried out vide plate bearing tests or pressuremeter tests conducted in boreholes at the required depths. 

Similar to the above section, plate bearing tests or pressuremeter tests carried out in boreholes are applicable for the assessment of bearing capacity and settlement. For initial reference to assess engineering properties of engineered fill, empirical chart and table in NAVFAC (1971) manual publication reproduced in Figure 3.12 and Table 3.9 may be of assistance. 

Pressuremeter tests (PMT) were also carried out and the results obtained were shown in Figure 3.18. Based on the PL results above, the undrained shear strength, Su of the ground was determined following Amar et al. (1991). Together with the Su determined from Field Vane Shear (FVS) and Cone Penetration Test (CPT) for the same site, some statistical analysis was carried out to compare the scatter of the results as shown in Table 3.11. 

Amar S., Clarke B.G.F., Gambin M.P. OrrT.L.L. 1991. The application of pressuremeter test results to foundation design in Europe. A state-of-the-art, report by ISSMFE European Technical Committee on... 

Clarke, B.G. 1990. Consolidation characteristics of clays from self-boring pressuremeter tests. In Field Testing in Engineering Geology, Engineering Geology Special Publication No. 6, Bell, F.G., Culshaw, M.G., Cripps, J.C. and Coffey. J.R. (Eds.), Geological Society, London, 33-37. 

Menard, L. F. 1975. Interpretation and Application of Pressuremeter Test Results, Sols-Soils, Paris, Vol. 26, pp. 1-23. 

---