Analytical solutions of limit support pressure and vertical earth pressure on cutting face for tunnels

This paper focuses on theoretical analytical models to calculate the limit support pressure and vertical earth pressure on the cutting face for tunnels.The failure zone is divided into two parts:a sliding failure zone and an upper loosen zone,and the limit support pressure calculation equation is derived.To verify the rationality of the theoretical model,it was compared with the existing theory,numerical simulation,and centrifugal test,and then the parameter analysis was carried out.The results show that the results of this paper agree well with the existing theory,numerical simulation,and centrifugal test.The inclination angle of the proposed mechanism is determined based on the results of the existing centrifuge test,and the recommended inclination angle is between 52°+φ/2 and 54°+φ/2.The method is proven to be safe and accurate.It can provide a theoretical basis for similar projects.

A novel conceptual design of a biomimetic oral implant and its biomechanical effect on the repairment of a large mandibular defect

This study aimed to propose a novel biomimetic design strategy of an oral implant and to numerically examine its biomechanical effect according to clinical interests.The designed implant conceptually mimicked the morphology and elastic modulus of the mandibular bone.Basing on a CT-image-based patient-specific reconstruction of the tumor-excised mandible,the biomechanical effects of the implants with three materials(PEEK/n-HA/CF,PEEK/HA and Ti6Al4V),two surgical conditions(removed and retained muscles),and two postoperative stages(early and late)were fully investigated by a static finite element analysis.Moreover,according to clinical interests(e.g.failure and stability of the implant and rivets),maximum von Mises stresses and strains of the implant and rivets,maximum implant-bone gap in the early postoperative stage,and maximum von Mises stress of the mandible were mainly analyzed.The results showed that the implant composed of Ti6Al4V material was suitable for the current design strategy with respect to the other two PEEK-based materials.Although the implants in the muscle-retained surgical condition had relative greater indices compared to the muscle-removed surgical condition,the index difference between the two conditions was slight.The biomechanical indices indicating the failure and loosening risks of implant and rivets were much reduced in the late postoperative stage with respect to the early postoperative stage due to the osteointegration at the implant-bone interface.Generally,the proposed novel design strategy could be useful to guide the design of the oral implant addressing different implant materials and surgical conditions,and further made proper suggestion to clinicians and patients.