In prior art vertical drain methods, paper drain materials are embedded vertically into the ground by embedding means such as a mandrel and then the mandrel is withdrawn. The lower end of the drain is usually provided with an anchor so that once the vertical drain has been properly positioned depthwise, the lower end of the vertical drain is anchored at the desired soil depth, thereby enabling the mandrel to be withdrawn without disturbing the vertical drain. However, for various reasons, such as mandrel contamination, soil pressure and/or water pressure, the drain sometimes does not become anchored as intended but instead adheres to and follows the mandrel upwardly as it is withdrawn from the soil, When this occurs and is detected, it is necessary to reposition the drain. Unfortunately, it is not always possible to know if a drain is improperly positioned since it may follow the mandrel upwardly for some distance and then become disengaged, leaving the drain embedded out of sight but not at the desired depth or vertical alignment.
USPTO Backgrounds
USPTO Backgrounds