Investigation of grouting diffusion in a single rock fracture considering the influences of obstructions

Grouting reinforcement was used to improve rock strength and avoid seepage in rock engineering. A self-developed visualised test platform was developed and the influences of different fracture openness on grouting diffusion modes were revealed; the Bingham rheological model was imported to simulate the grouting diffusion process in a single plate fracture, the spatio-temporal distribution of the velocity field under different obstructions was determined using the finite element method. The results indicate that: 1) The grout diffuses faster with the increase of fracture openness, while a stagnation effect of the grouting diffusion velocity behind the obstruction occurs. 2) Due to obstructions, the grouting diffusion process can be divided into four stages: circular diffusion, flat diffusion, vortex diffusion, and butterfly diffusion. 3) The grouting diffusion area is divided into a fully-reinforced zone and a semi-reinforced zone, and the area of the latter increases with the fracture openness, while being little affected by the size of any obstruction. 4) Furthermore, some new grouting diffusion laws were revealed considering the asymmetrical arrangement of obstructions. The results presented in this work will be helpful for describing and predicting the grouting process in fracture networks.

Simplified Mechanical Tests Can Simulate Physiological Mechanics of a Fixation Construct for Periprosthetic Femoral Fractures

Plate fractures after fixation of a Vancouver Type B1 periprosthetic femoral fracture (PFF) are difficult to treat and could lead to severe disability. However, due to the lack of direct measurement of in vivo performance of the PFF fixation construct, it is unknown whether current standard mechanical tests or previous experimental and computational studies have appropriately reproduced the in vivo mechanics of the plate. To provide a basis for the evaluation and development of appropriate mechanical tests for assessment of plate fracture risk, this study applied loads of common activities of daily living (ADLs) to implanted femur finite element (FE) models with PFF fixation constructs with an existing or a healed PFF. Based on FE simulated plate mechanics, the standard four-point-bend test adequately matched the stress state and the resultant bending moment in the plate as compared with femur models with an existing PFF. In addition, the newly developed constrained three-point-bend tests were able to reproduce plate stresses in models with a healed PFF. Furthermore, a combined bending and compression cadaveric test was appropriate for risk assessment including both plate fracture and screw loosening after the complete healing of PFF. The result of this study provides the means for combined experimental and computational preclinical evaluation of PFF fixation constructs.

Clinical and radio graphic evaluation of periotome in single rooted teeth

To evaluate the efficacy of periotome (Group p) in a traumatic extractions of single rooted teeth and to compare clinically and radio graphically with normal forceps extraction (Group c) in a sample of 30 patients. 30 patients -15 in each group (i.e. periotome and control group) were included in this randomised prospective comparative clinical study. Clinical parameters assessed were pain, buccal cortical plate fracture, gingival lacerations, soft tissue injury, teeth fracture, time taken for extraction, number and frequency of analgesics consumed and any post-operative complications were evaluated. Radiographic parameters of crestal alveolar bone levels were measured at pre operative, 1st month and 3rd month intervals by standardised IOPA using the grid in SOPRO imaging software, RVG.Comparing group C and P, statistically significant (p value <0.05) amount of MCABL bone loss is seen between preoperative to 3rd month and from 1st month to 3rd month in periotome group. The periotome group showed gingival of grade 1. Fracture of buccal cortical plate was seen in 26%, 2 cases of teeth fracture. Patients in the control group had more pain and increased analgesics consumption.Extraction of single rooted teeth can be done by periotomeatr aumatically which gives better ridge contours for future prosthetic rehabilitation.

Treatment of Femoral Non-Union with the Gene-Activated Osteoplastic Material: А Case Report

Background. Non-unions of distal femur fractures are difficult to treat and occur in about 6% of cases. Multifactorial causes of fractures non-unions require individual treatment for each patient in accordance with the “diamond” concept. The standard protocol for patients with atrophic non-unions treatment involves bone autografts using, but there are limitations of size, shape, quality and quantity of autografts. Osteoplastic materials with osteoinductive (angiogenic) and osteoconductive activity can be used as bioresorbable implants in combination with autogenous spongy bone in the treatment of extremities long bones non-unions.Clinical case description. A 63-year-old patient was admitted to the clinic for non-union of distal third of the femur with bone defect, fragments were fixed with a plate. The examination revealed plate fracture, screws migration (group III according to the Non-Union Scoring System). The volume of supposed bone defect was about 8.5 cm3. The surgery was performed: plate removal, debridement of the non-union zone, femur defect replacement with a bone autograft in combination with the gene-activated osteoplastic material “Histograft” in a ratio of 1:1, osteosynthesis of the femur with two plates. After 6 months. during the control computed tomography, consolidation was determined (4 points on the REBORNE scale). Pain was practically absent (NRS-2). The range of motion in the knee joint: flexion — 80o, extension — 180o. According to the Knee Society Score (KSS) — 68 points.Conclusion. In this case report the complete fracture fusion was achieved in patient within 6 months — 4 points on the REBORNE scale. No adverse events were observed. It confirms the safety and efficacy of described method and allows to continue the clinical trials.

Fatigue Resistance and Failure Behavior of Penetration and Non-Penetration Laser Welded Lap Joints

Penetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars, while their fatigue performances and the difference between them are not completely understood. In this study, the fatigue resistance and failure behavior of penetration 1.5+0.8-P and non-penetration 0.8+1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated. The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance, and their hardness was lower than that of the plates. The 1.5+0.8-P joint exhibited better fatigue resistance to low stress amplitudes, whereas the 0.8+1.5-N joint showed greater resistance to high stress amplitudes. The failure modes of 0.8+1.5-N and 1.5+0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture, respectively, and the primary cracks were initiated at welding fusion lines on the lap surface. There were long plastic ribs on the penetration plate fracture, but not on the non-penetration plate fracture. The fatigue resistance stresses in the crack initiation area of the penetration and non-penetration plates calculated based on the mean fatigue limits are 408 MPa and 326 MPa, respectively, which can be used as reference stress for the fatigue design of the laser welded structures. The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.