Safe, cost-effective tunnel construction is possible when the ground is stabilized in a reasonable pace. To ensure that an optimized support system is used, detailed in-situ geological data is needed. Currently, one of the main measures to address this issue is monitoring the ground and support components (i.e. in SEM or NATM systems). However, improving ground support requires reliable data. The most common support system used in underground spaces is rock-bolt, its drillhole can be used for probing and obtaining geological data, e.g. rock strength. This paper will introduce a recently developed probe (Rock Strength Borehole Probe) designed to estimate the rock strength by scratching the borehole wall. The probe uses a micro-controller to record the data from various sensors onto a mini-SD card. RSBP applications and design considerations will be discussed in this paper, along with the results of preliminary laboratory and field tests.
Assessment of rock mass properties is an essential part of analyzing stability of any surface or underground structure in rock. Availability of geological information including condition and frequency of discontinuities as well as rock strength is the crucial component of such analysis. One of the important parameters in evaluating rock mass properties is the intact rock strength. This parameter is usually measured by testing the core samples, obtained from exploration borings or from coring outcrop boulders. These core specimens are subsequently tested in rock mechanic laboratories. The test results offer limited information about the rock at the few locations along the borings despite all the efforts, time, and costs allocated for it. Moreover, the results may not necessarily be representative of the behavior of the rock in the field since the test cannot provide assessment for the impact of in-situ condition of the ground. The ideal solution is to be able to estimate the rock properties in-situ, preferably inside exploration borings or other drilled holes in an underground space. Therefore, the objective of the current study was to develop a method for evaluation of rock strength in various type and size boreholes to assess in-situ rock strength.
