The occurrence of shear failure in a rock mass, resulting from the sliding of joint surfaces, is primarily influenced by the surface roughness and contact area of these joints. Furthermore, since joints serve as crucial conduits for the movement of water, oil, gas, and thermal energy, the aperture and geometric complexity of these joints have a significant impact on the hydraulic properties of the rock mass. This renders them critical factors in related industries. Therefore, to gain insights into the mechanical and hydraulic behavior of a rock mass, it is essential to identify the key morphological characteristics of the joints mentioned above. In this study, we quantified the morphological characteristics of tensile fractures in granitic rocks using X-ray CT imaging. To accomplish this, we prepared a cylindrical sample of Hwang-Deung granite and conducted splitting tests to artificially create tensile fractures that closely resemble rough joint surfaces. Subsequently, we obtained 2D sliced X-ray CT images of the fractured sample with a pixel resolution of approximately 0.06 mm. By analyzing the differences in CT numbers of the rock components (e.g., fractures, voids, and rock matrix), we isolated and reconstructed the geometric information of the tensile fracture in three dimensions. Finally, we derived morphological characteristics, including surface roughness, contact area, aperture, and fracture volume, from the reconstructed fracture.

The hydro-mechanical behavior of rock mass in natural barriers is a critical factor of interest, and it is mainly determined by the characteristics of the fractures distributed in the rock mass. In particular, the aperture and contact area of the fractures are important parameters directly related to the fluid flow and significantly influence the hydro-mechanical behavior of natural barriers. Therefore, it is necessary to analyze the aperture and contact area of fractures distributed in potential disposal sites to examine the long-term evolution of the natural barriers. This study aims to propose a new technique for analyzing the aperture and contact area using the natural fractures in KURT (KAERI Underground Research Tunnel), an underground research facility for the deep geological disposal of high-level radioactive waste. The proposed technique consists of a matching algorithm for the three-dimensional point cloud of the upper and lower fracture surfaces and a normal deformation algorithm that considers the fracture normal stiffness. In the matching process of upper and lower fracture surfaces, digital images obtained from compression tests with pressure films are used as input data. First, for the primary matching of the upper and lower fracture surfaces, an iterative closest point (ICP) algorithm is applied in which rotation and translation are performed to minimize the distance error. Second, an algorithm for rotation about the x, y, and z axes and translation in the normal direction is applied so that the contact area of the point cloud is as consistent as possible with the pressure film image. Finally, by applying the normal deformation algorithm considering the fracture normal stiffness, the aperture and contact area of the fracture according to the applied normal stress are derived. The applicability of the proposed technique was validated using 12 natural fractures sampled from KURT, and it was confirmed that the initial apertures were derived similarly to the empirical equation proposed in the previous study. Therefore, it was judged that the distribution of apertures and contact areas according to applied normal stress for laboratory-scale fractures could be derived through the technique proposed in this study.

With the increase of temporarily-stored radioactive waste in Korea, the disposal of radioactive waste in a deep geological repository, which is located in crystalline rock at a depth of hundreds of meters below the ground level, has received great attention nowadays. To ensure the permanent isolation of radionuclides from the human and surrounding ecosystems, the safety assessment for the high-level radioactive waste disposal facilities is essential. For the reliable safety assessment of fractured rock, it is especially important to input proper hydraulic properties of fractures such as aperture and hydraulic conductivity, which can directly affect the fluid flow and radionuclide transport. Meanwhile, it has become important to consider sudden fault behavior caused by an earthquake with the recent occurrence of high-intensity earthquakes in the Korean Peninsula. The sudden fault behavior can induce the changes of the hydraulic properties of fractures. Since the changes of the hydraulic properties directly affects to the radionuclide transport in the fractured rock, it is important to estimate the effect of earthquake-induced stress change on hydraulic properties of fractures in the perspective of long-term safety assessment. In this study, the effect of an earthquake on the hydraulic properties of fractures was explored by a numerical approach. The static Coulomb stress change after the earthquake was calculated using software ‘Coulomb 3’ developed by United States Geological Survey (USGS) with the assumption for several mechanical properties such as Young’s modulus, Poisson’s ratio and effective coefficient of friction. The final stress after earthquake occurrence was calculated as the sum of the initial stress and the stress change. Thereafter, the normalized transmissivity of fracture after the earthquake was calculated using the final stress from the stress-transmissivity relationship. Using the methodology for calculating fracture transmissivity change induced by the earthquake developed in this study, the effect of several factors, such as the earthquake magnitude and the distance between fracture and epicenter, was additionally explored. The newly developed methodology will be applied to the processbased total system performance assessment framework (APro) being developed by KAERI, and this study is expected to be helpful for the safety assessment considering long-term evolution phenomena including earthquakes.

Patients referred to the Veterinary Medical Center at Chungbuk National University were analyzed. This study aimed to provide information to clinicians in Korea on the factors affecting fracture incidence in patients adapted to Korean companion animal culture. Eighty cases showing- bone fractures were investigated from January, 2005 to De- cember, 2011. Fractures were mainly observed in miniature dogs such as Yorkshire terrier (12%), Poodle (12%), and Maltese (9%). Almost 50% of all cases were less than 1 year old. Total bone fractures in summer and fall constituted 62%. Fracture incidence was higher in male dogs (54%) than female dogs (46%). Hindlimb fracture (37%) was the most common. Distribution of limb fractures was higher in the femur (19), followed by the tibia/fibula (15), radius/ulna (13), humerus (11), and mandible (8). Pelvic fracture was observed in 19 cases. Simple fracture (84%) was the most common fracture type, followed by comminuted fracture (16%). Distal portion was the most common fracture site in long bones (67%), followed by middle (26%) and proxi- mal bones (7%). Fractures were mainly caused by traffic accidents (43%), whereas 28.5% of fractures were due to falling down. Plate & screw (26%) was the most common method of fracture repair, followed by intramedullary pin (24%), wire (11%), external skeletal fixation (10%), screw (9%), amputation (7%), cross pin (6%), IM pin and wire (5%), and rush pin (1%). Among 80 patients, 79%of pa- tients showed a good prognosis after surgery, whereas 13% patients did not experience a good result. This study shows that miniature dogs are prone to falling and fractures, espe- cially in the distal part of long bones.

Laboratory experiments were conducted in order to find effects of the intermediate principal stress of σ2 on rock fractures and faults. Polyaxial tests were carried out under the most generalized compressive stress conditions, in which different magnitudes of the least and intermediate principal stresses σ3 and σ2 were maintained constant, and the maximum stress σ1, was increased to failure. Two crystalline rocks (Westerly granite and KTB amphibolite) exhibited similar mechanical behavior, much of which is neglected in conventional triaxial compression tests in which σ2 = σ3. Compressive rock failure took the form of a main shear fracture, or fault, steeply dipping in σ3 direction with its strike aligned with σ2 direction. Rock strength rose significantly with the magnitude of σ2, suggesting that the commonly used Mohr-type failure criteria, which ignore the σ2 effect, predict only the lower limit of rock strength for a given σ3 level. The true triaxial failure criterion for each of the crystalline rocks can be expressed as the octahedral shear stress at failure as a function of the mean normal stress acting on the fault plane. It is found that the onset of dilatancy increases considerably for higher σ2. Thus, σ2 extends the elastic range for a given σ3 and, hence, retards the onset of the failure process. SEM inspection of the micromechanics leading to specimen failure showed a multitude of stress-induced microcracks localized on both sides of the through-going fault. Microcracks gradually align themselves with the σ1-σ2 plane as the magnitude of σ2 is raised.

We evaluated the radiologic, clinical results and the complications of minimally invasive percutaneous medial plate fixation in distal tibial metaphyseal fracture. From January 2010 to December 2016, 31 patients with distal tibial fracture treated by medial plate fixation using Minimal Invasive Plate Osteosynthesis (MIPO) technique were analyzed. The duration of followup was more than 1 year. We evaluated clinical results by IOWA ANKLE rating system, union time by simple X-ray and complication. The bone union was achieved in all cases at average 16.7 weeks. Average IOWA ANKLE rating score was 90.3 point. At the last follow-up, there was no non-union, angular deformity more than 5 degrees or infection. We concluded that minimal invasive percutaneous medial plate fixation for distal tibial metaphyseal fractures is a safe and useful method if there is no medial wound problem, and it is important to pay close attention to prevent angular deformity during surgery.

We report the good results of two stage treatment in split depression type pilon fractures. A retrospective study of 9 cases among the 12 cases of split depression type pilon fractures from January 2009 to December 2015, who underwent two stage treatment of pilon fractures with minimum 24 months follow-up. And mean follow-up periods are 29 (24-41) months. In the first stage of the operation, reduction of articular surface using minial incision and external fixation were performed. As soft tissue heals, locking compression plate fixation was done with MIPO (Minimally Invasive Plate Osteosynthesis) technique. Radiographic evaluation was graded by the criteria of Burwell and Charnley. And functional assessment of ankle were evaluated by American Orthopaedic Foot and Ankle Society ankle-hindfoot score. Fractures were united in all cases within 17 (12-24) weeks. Radiologic results were showed anatomical reduction in 8 cases and the mean AOFAS score is 87.8 (80-96). The mean range of ankle motion is 44 degree. There are one superficial wound complications and 3 cases of ankle osteoarthritis. Two stage treatment of split depression type pilon fractures is one of the good treatment methods, because of definitive second stage operation is more easier after first stage opertation designed to get early anatomical reduction, and shows good radiological and clinical outcomes.

Due to the thick cortical structure, subtrochanteric fractures of femur is often caused by high energy trauma and there are only a few report of it from low energy trauma. We have experienced a case of bilateral subtrochanteric fracture which oc-curred after a simple slip down. The fracture was healed with applying intramedullary nail. We believe the fracture may have occurred from prolonged use of steroid which was used to treat underlying rheumatoid arthritis.

This manuscript is reporting the usefulness and treatment results of internal fixation with PHILOS plate in proximal humerus fractures with osteoporosis. Sixteen cases of proximal humerus fractures with osteoporosis were surgically treated with PHILOS plate and followed up for an average 11 months (8-23 months). Mean age was 63 years old (range, 47-88 years old). The functional results were assessed by Neer’s evaluation criteria, Constant evaluation criteria and Korea shoulder scoring system. And the radiological results were assessed by Paavolainen’s method. The mean BMD T- score is -3.5, the mean bone union periods were 15.9 weeks. Functional satisfactory results were thirteen cases in Neer’s evaluation criteria, good results were fourteen cases in Constant evaluation criteria and the mean score is eighty-nine points in Korea shoulder scoring system. Radiologic good results were noted in thirteen cases and fair results were noted in one case. One case showed screw loosening in complication. Internal fixation using PHILOS plate for proximal humerus fractures with osteoporosis makes good functional and radiologic results, so that is considered as a good method.

The purpose of this study was to develop guidelines to improve the health of an elderly population classified into unilateral and bilateral hip fracture groups based on the mortality and risk factors affecting survival time. In the bilateral fracture group, the incidence of fracture was 3.1%, whereas mortality was 35%, average age was 83.9, and the male to female ratio was 3:17. In patients older than 75 years of age with a unilateral fracture, close ambulatory follow up is needed to avoid bilateral fracture and protect against secondary fracture within 3 years.