Roof bolting is the most popular method for underground openings in the mining industry, especially in the bedded deposits such as coal, potash, salt etc. In fact, all U.S. underground coal mine entries are roof-bolted as required by law. However, roof falls still occur frequently in the roof bolted entries. The two possible reasons are: the lack of knowledge of and technology to detect the roof geological conditions in advance of mining, and lack of roof bolting design criteria for modern roof bolting systems. This research is to develop a method for predicting the roof geology and stability condition in real time during roof bolting operation. Based on such information, roof bolting design criteria for modern roof bolting systems will be developed for implementation in real time. More laboratory tests have been performed in this quarter. The analysis performed on the testing data showed: (1) abnormal rotational accelerations can be used as the indicator of the rock interfaces, and (2) the sharp drops of drilling thrust and torque agree well with the locations of fractures.

Roof bolting is the most popular method for underground openings in the mining industry, especially in the bedded deposits such as coal, potash, salt etc. In fact, all U.S. underground coal mine entries are roof-bolted as required by law. However, roof falls still occur frequently in the roof bolted entries. The two possible reasons are: the lack of knowledge of and technology to detect the roof geological conditions in advance of mining, and lack of roof bolting design criteria for modern roof bolting systems. This research is to develop a method for predicting the roof geology and stability condition in real time during roof bolting operation. Based on such information, roof bolting design criteria for modern roof bolting systems will be developed for implementation in real time. More field tests have been performed. A trendline analysis method has been developed. This method would improve the accuracy in detecting the locations of fractures and in determining the rock strength.

In this quarter, the research effort is to develop the drill control unit (DCU) that acquire, store drilling parameters and control the drilling operation. The relevant publications have been reviewed and the methodology developed by previous researchers has been evaluated using the collected data in our laboratory and field tests conducted prior to the start of this project. Numerical modeling for exploring roof bolting mechanism has been started.

In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) one more field test has been conducted in an underground coal mine, (2) optimization studies of the control parameters have been conducted, (3) the relationship among feed pressure, penetration rate and rotation rate seems to be a good indicator for estimating rock strength when both penetration rate and rotation rate are controlled or kept constant, (4) the empirical equations for eliminating the machine effect on drilling parameters were developed and verified, and (5) a real time roof geology mapping system for roof bolters in limestone mine, including a special version of the geology mapping program and hardware, performs very well in underground production condition.

A one-year non-cost extension has been granted for this project. In this quarter, the field, theoretical and programming works have been performed toward achieving the research goals set in the proposal. The main accomplishments in this quarter included: (1) laboratory tests have been conducted, (2) with the added trendline analysis method, the accuracy of the data interpretation methodology will be improved and the interfaces and voids can be more reliably detected, (3) method to use torque to thrust ratio as indicator of rock relative hardness has also been explored, and (3) about 80% of the development work for the roof geology mapping program, MRGIS, has completed and a special version of the program is in the field testing stage.