It is well known that there is an inherent variability in the values of undrained shear strength of soil collected at different depths. In the case of natural deposits, this variability is attributed to the randomness associated with the geological processes involved in the formation of the deposits. The study on spatial variability of soil properties like undrained shear strength (Su), cone bearing (qc) and pore pressure(delta u), is the main goal of this thesis. Probabilistic and Statistical approaches have been applied to analyze results of cone penetration tests performed in quartenary soft clay deposits located in the Baixada Santista - Sao Paulo, gneiss residual soil profile - Experimental Campus - PUC-RIO and also in a Tailing dam at Paracatu - MG. Vane, Menard and self-boring Pressuremeter tests have been used to establish the scale of fluctuation through the study of autocorrelation functions in a quartenary soft clay deposit located in the Baixada Santista area. The results of that study have shown that, for piezocone tests in the residual soil and soft clay in the Baixada Santista, the best Probability Density Function will be Lognormal, and that fluctuation scale obtained from piezocone, Vane, Menard and self-boring pressuremeter tests are an important descriptor of soil variability.