Significance of a new preliminary treatment method of the Pen206_18 borehole penetrometer’s pressure readouts for a reliable analysis of rock stress-strain parameters

This article describes some selected aspects of a preliminary treatment of measurement cycle results obtained by a new Pen206_18 type hydraulic borehole penetrometer (a borehole jack type), a tool of an in situ determining of mechanical properties of rocks. The pre-treatment of the measurement cycle results is a necessary step to prepare the data for a following appropriate analysis of stress-strain parameters of rocks. Aforementioned aspects are focused mainly on a pre-treatment of hydraulic pressure readouts. The Pen206_18 type penetrometer is a modified version of a standard Pen206 type penetrometer. The standard version, based on a digital measurement of a critical hydraulic pressure, has been in use in polish hard coal mines for almost 15 years to determine various rock strength parameters. In contrary, the Pen206_18 type penetrometer now provides simultaneous recording of two main measurement cycle parameters (hydraulic pressure and a head pin stroke) during the whole measurement cycle duration. A recent modification of the penetrometer has given an opportunity to look closer at various factors having an influence on the measurement cycle data readouts and, as a consequence, to lay a foundation for a development a new penetrometric method of determining stress-strain parameters of rocks. In this article it was shown that just before a main stage of the measurement cycle, a transitional stage could occur. It complicates a determination of the beginning of an useful set of measurement cycle data. This problem is widely known also in other static in situ methods of determining stress-strain parameters. Unfortunately, none of various known workouts of this problem were sufficiently adequate to the pre-treatment of the penetrometric measurement cycle results. Hence, a new method of determining the beginning of the useful set of pressure readouts has been developed. The proposed method takes into account an influence of an operational characteristics of the measuring device. This method is an essential part of a new pre-treatment procedure of the Pen206_18 measurement cycle’s pressure readouts

A Pen206 borehole jack suitability assessment for rock mass deformability determination

Currently available field rock mass deformability determination methods are rather difficult to perform, due to their complexity and a time-consuming nature. This article shows results of a suitability assessment of a Pen206 borehole jack (a hydraulic penetrometer) for field rock mass deformability measurements. This type of the borehole jack is widely used in Polish hard coal mining industry. It was originally intended only for quick rock mass strength parameters determination. This article describes an analysis and scope of basic modifications performed mainly on a borehole jack head. It includes discussion of results with possible directions for future development of the device