Vane Shear Test

Torque is applied to the vanes using an electric motor to rotate the vanes at a standard of 0.10 per second. This rotation of the vanes develops a cylindrical failure surface. The torque 

General range of variation of q/N for various types of soil. (From Robertson, RK., and Campanella, R.G., Canadian Geotech. ]., 20, 718-733,1983. Reprinted with permission of the Canadian Geotechnical Journal.) 

K is the vane constant depending on the dimension and shape of vane in metric units 

The device for field applications has been standardized by American Society for Testing and Materials (ASTM D2573). A symposium on vane testing was held by ASTM in 1988 (Richards, 1988). Sources of error in the vane shear test are poor calibration of torque measurement, damaged vanes, or variation in rate of vane rotation. 

For normally consolidated clay deposits in the Gulf of Mexico and many other regions of the world. 

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ASTM S5unposium on Vane Shear Testing Laboratory and In Situ Measurements, STP 1014,1989... 

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. 

The vane shear test is a wireline tool used during the drilling operation to determine the in situ (field) undrained shear strength (S ) of soft to medium stiff clay soils. The vane shear apparatus consists of four blades placed on the end of a rod (Figure 4.20). The height (H) of the vane is standardized as twice the diameter (D). The vanes can be either rectangular or tampered. To use in the field, the vanes of the apparatus are pushed into the sediment at the bottom of the borehole. This operation produces very little soil disturbance. 

Bjerrum (1972) recommended that the field vane shear test values be correlated as follows for actual design purposes ... 

Vane shear test correction factor as a function of plasticity index. (From Bjerrum, L., Embankments on soft ground. Proceedings on Performance of Earth Supported Structures, American Society of Civil Engineers, 11, 1-54, 1972. Reprinted with permission of ASCE.)... 

The laboratory miniature vane shear test consists of inserting a four-bladed vane into a sediment section and rotating the vane at a constant rate of rotahon until a peak torque is reached. Details on computing vane shear strength has been previously presented in Chapter 5 for a field test. The same equations are used for the laboratory test. 

Bjerrum 1. Laboratory miniature vane 2. Atterberg limits o tj a o u Perform Atterberg limit and laboratory vane shear test. Correct results usii the following equation u(field) A(lab) Correction factor curve developed from back calculation of terrestrial slope failures Bjerrum (1972)... 

Richards, A.R, ed. 1988. Vane Shear Testing in Soils Field and Laboratory Studies. ASTM STP 1014. 

ASTM D2573. Standard Test Method for Field Vane Shear Test in Cohesive Soil. 

Young, A.G., McClelland, B., and Quiros, G.W. 1983. In situ vane shear testing at sea. In International Symposium on Soil and Rock Investigations by In Situ Testing II, Paris, France. 

ASTM. D4648. Standard test method for laboratory miniature vane shear test for saturated finegrained clayey soil. In Annual Book of ASTM Standards, Section 4, American Society for Testing and Materials, Philadelphia, PA, Vol. 04.08, p. 9. 

Monney, N.T. 1974. An analysis of the vane shear test at varying rates of shear, In Deep Sea Sediments Physical and Mechanical Properties, Inderbitzen, A.L., ed.. Plenum Press, New York, pp. 151-167. 

Vane Shear Test This test measures the shear resistance of soils. It consists of forcing a vane with four orthogonal blades into the soil and rotating it until the soil fails. The maximum torque value is measured. 

For instance, data from the vane shear test in clays are usually analyzed within a limit equilibrium solution, whereas pressuremeter results are considered within cylindrical cavity expansion. Alternative theoretical solutions proposed for analysis of CPT data include limit plasticity, strain path method, finite elements, discrete elements, hybrid cavity expansion-critical state, and dislocation theory. Usually, the approaches are established for two extreme cases of drainage, either (a) undrained, applied to clays or (b) fully-drained, applied to sands. In reality, many possible scenarios lie between the two conditions, as discussed by Randolph (2004) and Schneider et al. (2008). 

Since the time of Skempton s work, a considerable amount of vane shear testing (VST) has been completed worldwide (e.g. Chandler 1988 Mayne Mitchell 1988 Leroueil Jamiolkowski 1991). These studies showed that raw vane shear strengths were better normalized by the yield stress (Suv/ffp and this ratio increased with PI in a nonlinear manner, but similar in trend to equation (la). The author has reviewed results from several compiled VST databases (Mayne 2007), with Figure 8 showing a full summary developed from n = 212 tests, indeed confirming the general trend that raw S = Suv/<7vo nc increases with the plasticity index of the soil. 

If the potential fill material has a cohesive nature, in-situ vane shear tests may be performed to determine the undrained shear strength (see section 3.4.2.1 and Appendix B.2.3.2). Alternatively, Cone Penetration Tests could be undertaken to indirectly assess the undrained shear strength using existing correlations (see Appendix C). Undisturbed samples of the cohesive strata could be recovered from boreholes which are subsequently tested in the laboratory. For more details on slope stability analysis reference is made to section 8.4.3.7 of this Manual. 

The undrained shear strength of cohesive material can directly be measured on site by means of the in-situ vane shear test. This test is also used to calibrate the correlation between the undrained shear strength and the cone resistance of a CPT or the N-value of an SPT. 

Undrained shear strength testing of cohesive material (e.g. clay) can be realised in the laboratory by means of the vane shear test or the triaxial test, type UU (Unconsolidated Undrained) or UCS (Unconfined Compression Strength) on undisturbed samples. In such triaxial tests, sample preparation and sample size may influence the results. 

A specific point of attention is that the results of vane shear tests need to be corrected for plasticity, anisotropy and rate effects according to the formula c, =p- Such a correction factor is based on experience. Bjerrum (1972) has... 

Figure 8.13 Correction of vane shear test results based on the liquid limit (w ) of the clay (EC7, Part 2, 2006).

The Vane Shear Test measures the actual value of the undrained shear strength in soft cohesive subsoil. The proportional strength increase due... 

The field vane shear test can be undertaken in boreholes formed by cable tool and wash boring methods. It is used to measure the shear strength of soft clays and clayey silts by means of a small vane, which is pushed into the soil. An increasing torque is applied to the vane until the cylinder of soil fails at which point the applied torque is noted. It is often the only way in which the shear strength of very soft soils can be measured reliably because of the difficulty of obtaining and testing truly undisturbed samples in such material. 

Field vane shear test Soft to firm clay. Undrained shear Carried out in... 

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