Variations in clay deposits of Chicago

The spatial variations of penetration resistance and water content in two till formations of the Chicago Clay were analyzed as random fields. The trend, variance and correlation distance were calculated. The variances of the two tills are very different. Within each till, the variance is not constant for different regions because spatial variations exist at different scales. Some of these have been traced to physical features such as silt inclusions. The trend with depth also varies with the location. These may also be related to textural changes in the till, although the data are not conclusive.