INJECTION MODEL OF CEMENT MORTAR PENETRATION INTO CRACKED ROCKS BEHIND WALLING

The natural and technological factors influencing on the depth of injection cement mortars penetration into the cracked rocks and emptiness under the lining of mountain tunnels have been studied. There are the width of cracks in rocks and groundwater pressure in them, the dynamic viscosity of the solution, which is determined by the content of additives-superplasticizer and watercement ratio W/C, the magnitude and duration of pressure during the projection (crimping). Thesefacts were established after the analytical of literature sources and the analysis of features, design and a technical condition of real tunnel, geological structure of processing rocks under their lining. Based on the fundamental rheological equation - Newton's law in viscous flow models of dependences of depth of penetration on factors mentioned above are developed. Because of research of these models the sizes of technological factors, including dynamic viscosity of the mortar, providing the required penetration of cement mortars were received. To ensure the penetration of the solution to a depth of 10 m in cracks with a width of 10 mm, the dynamic viscosity should not exceed over 0.05 Pa·s, and in cracks of 1 mm – 0.01 Pa·s. To ensure the penetration of the solution to a depth of 2 m in cracks with a width of 1 mm, the dynamic viscosity should be in the range of 0.03–0.1 Pa·s, and in cracks of 0.1 mm – 0.0025–0, 01 Pa·s. Superplasticizers allows reducing the dynamic viscosity ofsolutions to such values and effectively increasing the depth of their penetration into cracks and, as a result increasing the water resistance and load-bearing capacity of the fractured rock. The technology of injecting cement mortars with superplasticizer additives has been improved and developed for: the reconstruction of underground structures and massive artificial structures; the designing of a spherical bearing between galvanized concrete without a bald spot and the exposedmetal beams. The technology is recommended to be used for waterproofing and increasing the bearing capacity of tunnel, piers, bridges, and for the device of a laying layer between а withoutballast reinforced concrete bridge plate and longitudinal beams of metal bridges.

Bridge plating for simple tibial fractures treated by minimally invasive plate osteosynthesis

ABSTRACT This study aimed to evaluate the effectiveness of bridge plating of simple tibial fractures in dogs by minimally invasive plate osteosynthesis (MIPO). Medical and radiographic records of twenty-nine dogs with simple tibial fractures that underwent bridge fixation by MIPO were retrospectively evaluated. The clinical outcome was classified considering the presence of lameness at the end of the treatment. The tibial mechanical joint angles were measured and compared with the values described in the literature. Additionally, fragment apposition and implant disposition were evaluated. Based on the modified Radiographic Union Scale for Tibial fractures, the moment of clinical union was determined. Clinically, at the end of treatment, only one patient presented lameness at a trot. While there was no significant difference between the bone alignment in the frontal plane values and the values described in the literature (P>0.05), the caudal proximal tibial angle was significantly higher (P=0.001). The median fragment apposition was considered acceptable. The average bridge plate ratio, plate working length, and plate screw density were 0.8, 0.57, and 0.48, respectively. The median time to clinical union was 30 days. Bridge plating in simple tibial fractures resulted in fast healing and low complication rates.