Theoretical analysis of JMC effect on stress wave transmission and reflection

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.

Microbiologic risk factors of recurrent choledocholithiasis postendoscopic sphincterotomy

BACKGROUND Choledocholithiasis is a severe disorder that affects a significant portion of the world’s population.Treatment using endoscopic sphincterotomy(EST)has become widespread;however,recurrence post-EST is relatively common.The bile microbiome has a profound influence on the recurrence of choledocholithiasis in patients after EST;however,the key pathogens and their functions in the biliary tract remain unclear.AIM To investigate the biliary microbial characteristics of patients with recurrent choledocholithiasis post-EST,using next-generation sequencing.METHODS This cohort study included 43 patients,who presented with choledocholithiasis at the Guangdong Second Provincial General Hospital between May and June 2020.The patients had undergone EST or endoscopic papillary balloon dilation and were followed up for over a year.They were divided into either the stable or recurrent groups.We collected bile samples and extracted microbial DNA for analysis through next-generation sequencing.Resulting sequences were analyzed for core microbiome and statistical differences between the diagnosis groups;they were examined using the Kyoto Encyclopedia of Genes and Genomes pathway hierarchy level using analysis of variance.Correlation between the key genera and metabolic pathways in bile,were analyzed using Pearson’s correlation test.RESULTS The results revealed distinct clustering of biliary microbiota in recurrent choledocholithiasis.Higher relative abundances(RAs)of Fusobacterium and Neisseria(56.61%±14.81%vs 3.47%±1.10%,8.95%±3.42%vs 0.69%±0.32%,respectively)and the absence of Lactobacillus were observed in the bile of patients with recurrent disease,compared to that in stable patients.Construction of a microbiological co-occurrence network revealed a mutual relationship among Fusobacterium,Neisseria,and Leptotrichia,and an antagonistic relationship among Lactobacillales,Fusobacteriales,and Clostridiales.Functional prediction of biliary microbiome revealed that the loss of transcription and metabolic abilities may lead to recurrent choledocholithiasis.Furthermore,the prediction model based on the RA of Lactobacillales in the bile was effective in identifying the risk of recurrent choledocholithiasis(P=0.03).CONCLUSION We demonstrated differences in the bile microbiome of patients with recurrent choledocholithiasis compared to that in patients with stable disease,thereby adding to the current knowledge on its microbiologic etiology.

Comprehensive evaluation of high-steep slope stability and optimal high-steep slope design by 3D physical modeling

High-steep slope stability and its optimal excavation design in Shuichang open pit iron mine were analyzed based on a large 3D physical simulation technique. An optimal excavation scheme with a relatively steeper slope angle was successfully implemented at the northwest wall between Nos. 4 and 5 exploration lines of Shuichang Iron Mine, taking into account the 3D scale effect. The phys-ico-mechanical properties of rock materials were obtained by laboratory tests conducted on sample cores from exploration drilling directly from the iron mine. A porous rock-like composite material was formed for the model, and the mechanical parameters of the material were assessed experimentally;specifically, the effect of water on the sample was quantitatively determined. We adopted an experimental setup using stiff modular applied static loading to carry out a visual excavation of the slope at a random depth. The setup was equipped with acous-tic emission （AE） sensors, and the experiments were monitored by crack optical acquirement, ground penetrating radar, and close-field pho-togrammetry to investigate the mechanisms of rock-mass destabilization in the high-steep slope. For the complex study area, the model re-sults indicated a clear correlation between the model＇s destabilization resulting from slope excavation and the collected monitoring informa-tion. During the model simulation, the overall angle of the slope increased by 1-6 degrees in different sections. Dramatically, the modeled excavation scheme saved over 80 million tons of rock from extraction, generating enormous economic and ecological benefits.