Hallo Ehsan, here you are my answer second my in field experience. The first either instrumentation torvane (pocket) or shear vane (in borehole) have a same limit for a quick and a approximate determination of shear strength undrained value only on plastic saturated clays  without structural disturbances, not in hard clays. The hard clays normally are interested from  tectonic and thermic discontinuity. Torvane for a first very approximate value of soil. Moreover Is important that  the results of the test are not reliable for clays with sand or silt.The shear vane in borehole is better than torvane, but it must consider that the test area, when  the test is conduced from the bottom of borehole, it must be only three time the borehole diameter to avoid disturbance effects.

Vane shear can not be used for hard clay , is has been used for soft clay.

Hard clay you can use torvane (Penetrometer). 

1.  http://www.scdot.org/doing/technicalpdfs/geotechnicaldesign/chapter%2005%20field%20and%20laboratory%20testing%20procedures%20final%2007282008.pdf

hi Abdi, check out the above material. it helped me a great deal and I hope it would help you too. Good luck