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The key to safe and efficient mining of steeply dipping coal seams is an effective control of surrounding rock. Revealing the dip effect on mining mechanical behavior of coal-rock combination are the basis for the multi-scale surrounding rock collaborative control in steeply dipping coal seams. According to mechanical characteristics of coal-rock combination such as stress transfer between layers, principal stress deflection and non-equilibrium deformation and failure at different inclination angles, the dip effect of principal stress distribution and deformation and failure law in coal-rock combination is analyzed by research methods of rock mechanics experiment, numerical simulation and theoretical analysis combined with feedback.The results show that: when the angle changes in the range of 0°–60°, the evolution characteristics of the size and direction of the principal stress of the coal-rock combination at the interface are divided into two categories; When the dip angle is less than the critical angle α0, the first principal stress decreases with the increase of the dip angle, the third principal stress exhibits a monotonic evolution trend of “coal decrease + rock increase”, and the principal stress direction is a deflection state of “coal clockwise + rock counterclockwise”. When the angle is larger than the critical angle α0, the first principal stress of the coal-rock combination increases with the increase of the angle, the variation of the third principal stress increases, and the principal stress direction is in the deflection state of “coal counterclockwise + rock clockwise”. When the coal-rock combination is affected by the dip angle, the mechanical characteristics of the two states are different, so that the combined failure mode of coal-rock combination changes from “the rock mass on the upper side of the interface + non-interface part of the coal body” to “the lower side of the interface + non-interface part of the coal body”. That is, corresponding to the transformation of the shear deformation failure law of the composite body to the slip failure law at the interface. Therefore, the strength of coal-rock combi-nation decreases with the increase of dip angle. The research results reveal the non-equilibrium transfer law of stress in coal-rock combination and the dip effect of its failure mechanism, which has certain theoretical reference significance for the safe and efficient mining of steeply dipping coal seams.

The prognostic role of the Age-Adjusted Charlson Comorbidity Index (ACCI) in hilar cholangiocarcinoma patients undergoing laparoscopic resection is unclear. To evaluate ACCI's effect on overall survival (OS) and recurrence-free survival (RFS), we gathered data from 136 patients who underwent laparoscopic resection for hilar cholangiocarcinoma at Zhengzhou University People's Hospital between 1 June 2018 and 1 June 2022. ACCI scores were categorized into high ACCI (ACCI > 4.0) and low ACCI (ACCI ≤ 4.0) groups. We examined ACCI's association with OS and RFS using Cox regression analyses and developed an ACCI-based nomogram for survival prediction. Our analysis revealed that higher ACCI scores (ACCI > 4.0) (HR = 2.14, 95%CI: 1.37–3.34) were identified as an independent risk factor significantly affecting both OS and RFS in postoperative patients with hilar cholangiocarcinoma (p < 0.05). TNM stage III-IV (HR = 7.42, 95%CI: 3.11–17.68), not undergoing R0 resection (HR = 1.58, 95%CI: 1.01–2.46), hemorrhage quantity > 350 mL (HR = 1.92, 95%CI: 1.24–2.97), and not receiving chemotherapy (HR = 1.89, 95%CI: 1.21–2.95) were also independent risk factors for OS. The ACCI-based nomogram accurately predicted the 1-, 2-, and 3-year OS rates, with Area Under the Curve (AUC) values of 0.818, 0.844, and 0.924, respectively. Calibration curves confirmed the nomogram's accuracy, and decision curve analysis highlighted its superior predictive performance. These findings suggest that a higher ACCI is associated with a worse prognosis in patients undergoing laparoscopic resection for hilar cholangiocarcinoma. The ACCI-based nomogram could aid clinicians in making accurate predictions about patient survival and facilitate individualized treatment planning. [ABSTRACT FROM AUTHOR]