Cement Slurry Plugging Law and Optimal Plugging Flow Rate at a High Hydraulic Gradient

With the continuous development of coal and rock mass engineering, water inrush grouting has become an urgent problem in engineering disaster management. Herein, a theoretical model of the optimal plugging flow rate was established, and a comparative theoretical analysis was performed based on the results of indoor model tests. The particle incipient velocity was defined as the optimal plugging flow rate. The effects of hydrodynamic velocity, water-cement ratio, grouting pressure, and fracture aperture on the cement slurry grouting plugging were studied, and the optimal threshold of the plugging flow rate was obtained for theoretical model verification. Results showed that, at a high hydraulic gradient, the plugging effect of the grout was mainly affected by the hydrodynamic velocity, water-cement ratio, and grouting pressure (listed in the order of importance). When the hydrodynamic velocity was low, the difference in the slurry deposition thickness was large under different water–cement ratios and pipe diameters. When the hydrodynamic velocity was increased, the influence of various factors on the slurry deposition thickness decreased. Through a comparative analysis of the experimental and theoretical values, the optimal plugging velocity of pure cement slurry was 0.5–0.55 m·s−1 under different conditions, and the error between the experimental and theoretical values was less than 0.1 m·s−1, which confirmed the rationality of the proposed model.

Pengaruh Kedalaman Sudu Mangkok terhadap Unjuk Kerja Turbin Kinetik

The purpose of this study was to determine the effect of depth variations of the bowl blade on the performance of kinetic turbines. The test has conducted experimentally on a laboratory scale. In this study three vertical shaft, kinetic turbines were used with blade depth variations of 2 cm, 3 cm, and 4 cm. Each turbine will be tested on different rotation variations and flowrate variations. Parameters such as turbine power and efficiency will be determined based on the results of measurements of water velocity, water level, and braking load. The results showed that the depth of the bowl blade affected the performance of the kinetic turbine. The highest kinetic turbine performance was obtained in the turbine with 4 cm blade depth variation, followed by the turbine with 3 cm blade depth variation and the lowest turbine performance was obtained at 2 cm blade depth variation. The maximum performance of the turbine is obtained at 4 cm blade depth variation at 80 rpm and 65 m3/h water discharge, where the power generated is 13.2 Watts and efficiency is 34.5%.

A Water Slide Accident Resulting in an Open Book Pelvic Injury and Subsequent Pulmonary Embolus: A Case Report

Obesity and pelvic injuries are well-known independent risk factors for developing a pulmonary embolus; however, there is minimal literature with regard to obesity being a risk factor for suffering a pelvic injury from descending a water slide. We believe that obese patients are potentially at increased risk of receiving open book pelvic injuries on modern-day high-velocity water slides. To our knowledge, there are no other reports of a patient suffering an open book pelvic injury and a subsequent pulmonary embolus due to a water slide accident. We also propose a mechanism of injury for an obese person developing an open book pelvic injury from a water slide. An obese 46-year-old female descended on a thrill ride at a popular water park and sustained an open book pelvic injury. She subsequently developed a pulmonary embolus while awaiting open reduction and internal fixation of the anterior pelvic ring. One month post-injury, she had uneventful open reduction and internal fixation and went on to have an uneventful postoperative course. Patrons and amusement park owners should be aware of the increased risk an obese person is at when using a high-velocity water slide. There should be appropriate emergency personnel and equipment on site in anticipation of a possible high-energy injury.