Dynamic Rock-Breaking Process of TBM Disc Cutters and Response Mechanism of Rock Mass Based on Discrete Element

Rock-breaking efficiency of full-face rock tunnel boring machine (TBM) is closely related to the performance of the disc cutter and the characteristics of the rock mass. In the point of view of mesomechanics, the particle flow code (PFC) is used to establish a numerical model of the rock mass and the disc cutter, and the process of TBM disc cutter intrusion into the rock mass is analyzed. The dynamic response mechanism and crack evolution process of the rock mass under the action of the disc cutter are studied on the basis of micromechanics, and the relationship between the rock mass crack, penetration, and cutting force during the intrusion of the disc cutter is revealed. The sensitivity analysis is carried out on the confining pressure conditions and the influence parameters of the disc cutter spacing. The results show that the rock breaking by disc cutter undergoes the transformation characteristics of compaction, shearing, and tension failure modes, and the failure process of the rock mass is the joint action of tension and shear. In the whole process of rock breaking, the disc cutter has the phenomenon of repeated loading-unloading alternation and leaping rock breaking; after the penetration of the disc cutter reached 9.0 mm, penetration creaks begin to appear on the surface of the rock mass; the penetration was obviously reduced with the increase of confining pressure, and it is mainly the penetration cracks on the surface; after the disc cutter spacing reaches 100.0 mm, there is no penetration crack between the two disc cutters. The research conclusion can provide a reference for the disc cutter optimization design.

Constitutionalism within Times of Change: Authority, Society and Democracy

This article, following classical methodological patterns, as well as their evolution framework, identifies key features of the two most predominant constitutionalism traditions — political and legal, simultaneously drawing indispensable red lines with regard to correlation of the doctrine and a Fundamental Law itself. Respectively, the features have been rendered as the very elements of constitutionalism’s role within times of change — i. e., over the aforementioned time frames and transition states in between — whereas the doctrine’s capacity to answer so-called “questions of constitutionalism” constitutes its underlying response mechanism. The article addresses the phenomena of authority, society and democracy in their modern perception, and makes crucial points upon the constitutionalism’s effect on their sheer structures.

Tolerance of Electromagnetic Relay to Voltage Sags and Short Interruptions

This paper studies the tolerance of electromagnetic relay (EMR) under voltage sag and short interruptions on the basis of response mechanism analysis and the extensive tests. First, it introduces the structure of EMR and proposes response mechanism of EMR under voltage sag. Then, a detailed test plan is presented, including the information of test platform, testing condition, EMRs used in test, list of test, test procedure, and the measured waveforms. Magnitude and duration of the sags are not only the characteristics to be considered to investigate EMR’s tolerance. The other factors, which may have significance influence on tolerance of EMR, are considered here, including point-on-wave (POW), phase angle jump (PAJ), harmonic, magnitude variation in pre- and post-sag segments, two-stage sag, and slow recovery sag. Extensive tests results are presented in the form of voltage-tolerance curves (VTCs). Besides magnitude and duration, POW, PAJ, and two-stage sag have a significant influence on the tolerance of EMR. Other factors only have a tiny impact on the tolerance of EMR. The results show that the magnitude tolerance of EMR is 48–74% of Unom, and duration tolerance is 5–28 ms; they are useful for the technical assessment of EMR’s tolerance to voltage sags and short interruptions, and for the economic assessment of the industry process trip due to its disengagement. Test results also benefit for choosing proper EMR and mitigation device in the complicated operating environment.

Rock Thickness Identification by XGBoost with Logging Data

Based on research on the response mechanism of rock formations and reservoirs to logging curves, 12 logging curves selected by combining the depth characteristics of formations are proposed to identify rock formations and reservoirs using four algorithms: logistic regression (LR), support vector machine (SVM), random forest (RF) and XGBoost. Out of 60 wells in the study block, 57 wells were selected for training and learning, and the remaining 3 wells were used as prediction samples for testing the algorithm. The recognition of rock formations and reservoirs is performed by each of these four machine learning algorithms, and predictive knowledge is obtained separately. It was found that the accuracy of the 4 algorithms for rock formation and reservoir layer identification reached over 90%, but the XGBoost algorithm was found to be the best in terms of the 4 scoring criteria of F1-score, precision, recall and accuracy. The accuracy of rock formation identification could reach over 95%, and the correlation analysis between the logging curve and rock formation could be performed on this basis. The results show that the RMN, RLLD and RLLS have the most obvious responses to the sandstone layer, off-surface reservoir and effective thickness layer, and the CAL has the least effect on the formation and reservoir identification, which can provide an effective reference for the selection and dimensionality reduction of the subsequent logging curves.