Taking the joint matching coefficient(JMC) which represents the contact area ratio of the joint in rock masses as the key parameter, a one-dimensional contacted interface model(CIM-JMC) was established in this study t...Taking the joint matching coefficient(JMC) which represents the contact area ratio of the joint in rock masses as the key parameter, a one-dimensional contacted interface model(CIM-JMC) was established in this study to describe the wave propagation across a single joint. According to this model, the reflected and transmitted waves at the joint were obtained, and the energy coefficients of reflection and transmission were calculated. Compared with the modified Split Hopkinson pressure bar(SHPB) experiment, it was validated by taking the incident wave of the SHPB test as the input condition in the CIM-JMC, and the reflected and transmitted waves across the joint were calculated by the model. The effects of four sets of JMCs(0.81, 0.64, 0.49, and 0.36) on the transmission and reflection of the stress wave propagation across the joint were analyzed and compared with the experimental results. It demonstrated that the values of CIM-JMC could represent both the transmission and reflection of the stress wave accurately when JMC > 0.5, but could relatively accurately represent the reflection rather than the transmission when JMC < 0.5. By contrasting energy coefficients of joints with different JMCs, it was revealed that energy dissipated sharply along the decrease of JMC when JMC > 0.5.展开更多
This paper addresses the significance of preprocessing big data collected during a tunnel boring machine(TBM)excavation before it is used for machine learning on various TBM performance predictions.The research work i...This paper addresses the significance of preprocessing big data collected during a tunnel boring machine(TBM)excavation before it is used for machine learning on various TBM performance predictions.The research work is based on two water diversion tunneling projects that cover 29.52 km and 17051 boring cycles.It has been found that the penetration rate calculated from the raw measured penetration distances exhibits more random behavior owing to their percussive and vibratory behavior of the cutterhead.A moving average method to process the negative instantaneous velocities and a noise reduction filter to deal with signals with abnormal frequencies have been recommended.An index called the drilling efficiency index is introduced to assess the relationships between the mechanical parameters in a boring cycle,whose linear regression coefficient R^(2)is taken for a preliminary investigation of possible problems requiring preprocessing.The research work defines the irrelevant data whose errors are caused by human or mechanical mistakes,and therefore should be cleaned or amended.These irrelevant data can be divided into five categories:(1)premature cycles,(2)sensor defects,(3)mechanical defects,(4)human interruption,and(5)missing files.A program TBM-Processing has been coded for the recognition and classification of these categories.PDF books generated by the program have been uploaded at GitHub to encourage discussions,collaboration,and upgrading of the data processing work with our peers.展开更多
基金financially supported by the China Postdoctoral Science Foundation (No. 2017M620620)the Beijing Natural Science Foundation (No. 2184108)+2 种基金the Fundamental Research Funds for the Central Universities (No. FRF-TP-16-073A1)the National Science Foundation for Distinguished Young (No. 41525009)the State Key Research Development Program of China (Nos. 2016YFC0600703 and 2017YFC0804609)
文摘Taking the joint matching coefficient(JMC) which represents the contact area ratio of the joint in rock masses as the key parameter, a one-dimensional contacted interface model(CIM-JMC) was established in this study to describe the wave propagation across a single joint. According to this model, the reflected and transmitted waves at the joint were obtained, and the energy coefficients of reflection and transmission were calculated. Compared with the modified Split Hopkinson pressure bar(SHPB) experiment, it was validated by taking the incident wave of the SHPB test as the input condition in the CIM-JMC, and the reflected and transmitted waves across the joint were calculated by the model. The effects of four sets of JMCs(0.81, 0.64, 0.49, and 0.36) on the transmission and reflection of the stress wave propagation across the joint were analyzed and compared with the experimental results. It demonstrated that the values of CIM-JMC could represent both the transmission and reflection of the stress wave accurately when JMC > 0.5, but could relatively accurately represent the reflection rather than the transmission when JMC < 0.5. By contrasting energy coefficients of joints with different JMCs, it was revealed that energy dissipated sharply along the decrease of JMC when JMC > 0.5.
基金support from the National Program on Key Basic Research Project(973 Program,No.2015CB058100)of China and China Railway Engineering Equipment Group Corporationsupported by the Key Research Project of China Institute of Water Resources and Hydropower Research Limited(Grant Nos.HTGE0203A03201900000,HTGE0203A20202000000)Natural Science Foundation of Shaanxi Province(Grant Nos.2019JLZ-13,2019JLP-23).
文摘This paper addresses the significance of preprocessing big data collected during a tunnel boring machine(TBM)excavation before it is used for machine learning on various TBM performance predictions.The research work is based on two water diversion tunneling projects that cover 29.52 km and 17051 boring cycles.It has been found that the penetration rate calculated from the raw measured penetration distances exhibits more random behavior owing to their percussive and vibratory behavior of the cutterhead.A moving average method to process the negative instantaneous velocities and a noise reduction filter to deal with signals with abnormal frequencies have been recommended.An index called the drilling efficiency index is introduced to assess the relationships between the mechanical parameters in a boring cycle,whose linear regression coefficient R^(2)is taken for a preliminary investigation of possible problems requiring preprocessing.The research work defines the irrelevant data whose errors are caused by human or mechanical mistakes,and therefore should be cleaned or amended.These irrelevant data can be divided into five categories:(1)premature cycles,(2)sensor defects,(3)mechanical defects,(4)human interruption,and(5)missing files.A program TBM-Processing has been coded for the recognition and classification of these categories.PDF books generated by the program have been uploaded at GitHub to encourage discussions,collaboration,and upgrading of the data processing work with our peers.