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A reliable and robust visual perception system is often a key-enabler for autonomous robotic systems working in at least partially unknown environment. For autonomous robotic rock breaking system, boulder detection and localization system is an essential part that must be able to operate under challenging environments. The problem can be summarized as detecting unstructured objects in a structured environment. A key to robust boulder detection is an effective clustering algorithm, that can segment a point cloud, captured by e.g., a Time-of-Flight (TOF) camera, into clusters of individual boulders. This information is crucial for an autonomous robotic secondary breaking system, that uses it to break each individual boulder by a hydraulic impact hammer. This study proposes a novel algorithm for point cloud segmentation that can be used for the boulder detection application. The method is designed using features of the Point Cloud Library (PCL), and it is benchmarked against other readily available algorithms in the PCL. The results indicate robust performance with an impressive 97.4% accuracy on our dataset. acceptedVersion

As an important equipment for wellbore construction, the raise boring machine (RBM) has been widely used in subway tunnels and mine construction projects. Its tipped hob cutter for rock breaking is directly related to the cost, safety, and overall performance of the project. However, few open studies research on the rock-breaking by the tipped hob cutter, and there is still a lack of enough understanding of how the cutter breaks rock and the form of the rock breaking. In this paper, we study how the tipped hob cutter breaks the rock, and how to establish the finite-element model of the rock breaking by the cutter, with using the numerical simulation software LS-DYNA to analyze the rolling process and rock fracture form of the cutter. By studying the fracture morphology of rocks, it is proposed that there are three fracture modes of rock breaking: forward slip, no slip, and backward slip, using the experimental verification. On this basis, study the variation laws and correlations of feed force, lateral force, and positive force under different moving speeds and penetration depths. The results in this paper can provide a theoretical basis for improving the tool design of the tipped hob cutter on the RBM against the efficiency of rock-breaking.

As a new type of drilling method, with adding a certain proportion of steel particles into high-pressure pipe, high-velocity particle is formed to impact on rock surface to produce very large rock-breaking stress and achieve to drill rapidly. Therefore, based on cavity expansion theory, firstly, mathematical model of stress of particle impact rock was established, and the stress distribution of rock-breaking was numerical calculated. Then, the dynamical rock-breaking process under particle impact was simulated, and simulation results were compared with numerical calculation results. The results showed that there was a good agreement with each other, and rock-breaking stress could increase with increase of particle impact velocity. It would be of great significance to the development and improvement of particle impact drilling theory.

The study of bit-rock interaction model is essential to describe the rock breaking process. In practice, it is difficult to get downhole measurement, and the downhole rock-breaking data is difficult to obtain. Therefore, this paper uses finite element simulation to obtain the kinetic data of bit-rock interaction, based on the analysis and comparison of existing models, an effective analysis method is provided for bit-rock interaction. Firstly, by using the Drucker-Prager rock criterion, actual bit and rock parameters, we develop the finite element bit-rock interaction experiments, and we obtain the data of rotating speed, rate-of- penetration, weight-on-bit. Then, based on multiple nonlinear regression method, we identify the existing Young model, Jorden and Shirley model, Richard model, Ritto model parameters. Through the analysis and comparison of identification effects and characteristics of each model, we obtain the relationship among parameters of the bit-rock interaction.

The disc hob is a key component of the roadheader and its stress is complicated during the rock breaking process. In this paper, the finite element simulation analysis is carried out based on the external and internal actual force conditions of the disc hob. The research shows the rock breaking force of the hob is changing at any time. Through the thermal simulation during the rock-breaking process of the disc hob, it is found the thermal stress change trend is basically consistent with the temperature change trend. The value of the tool tip area is the largest and the value of the area farther from the tool tip is smaller. Through the comprehensive simulation analysis from different angles, it provides a certain basis for optimizing the structure of the disc hob, reducing the abnormal damage probability of the hob and prolonging the service life of the hob.

Analyzed the inadequacy of existing fracturing technology and combined with modern oil drilling technology, it discusses the rock breaking mechanism, range of application and technical features of this technology in this paper based on rock blasting theory. Then, it makes a careful analysis of stress about the surrounding rock when exploded, based on what it derived the dimension calculating formula of the crush zone and fracture zone. At last, depending on the explosive fracturing simulation tests which had been carried out with small amount of explosives, it verifies the accuracy of the dimension calculating formula. Studies show that the crushing effect is not obviously which explodes with a small amount of explosives, but it can get some clear macro-cracks; dimensions that calculated by formula which derived by this paper is basically consistent with the experimental measurements and has a reference value.

Based on fundamental theory and proceeding from major factor influencing the cone/bit speed ratio, the calculation model for calculating the average cone/bit speed ratio is to be derived. To contrast verify model calculated results with experimental results, they are closely coincide with each other. And further amend the model associating with tooth row and cone structural characters and drilling environment to make the cone/bit speed ratio more reasonable than calculation model. The cone/bit speed ratio calculation model is simple. The parameter in the model is precise and it is easy to get and convenient to calculate practically. The cone/bit speed ratio calculation model provides roller cone bit design, analysis and rock breaking mechanism research with effective theoretical foundation. The model is of high value for application.