Research of the resistance process of casing column filters at their contact with rock

The analysis of theoretical solutions and experimental data given in numerous literatures to justify the choice of the ratio of the size of gravel in relation to the size of formation sand showed that with the development of experimental methods and the accumulation of laboratory and field data, this ratio tends to decrease. When installing filters in an open hole, pressure losses at the interface between gravel and the formation play a significant role, and it should be noted that the greatest productivity and efficiency of the filter in an open hole is achieved when there is a packing around it, which can be created by crushing the sandy massif of the formation by cyclical changes debit. When choosing a filter design, along with the ability to provide them with a reliable hydraulic connection in the reservoir-filter system, the main task is also solved - to prevent sand flow into the well. The study of the conditions for the removal of sand particles through the flow sections in perforated, mesh and slotted filters during their operation both in homogeneous and in sands of different size, made it possible to recommend empirical dependences for determining the size of the holes. Keywords: porous medium; coarse fraction; sand; particle; well.

Optimal Proportion of Similar Materials and Rockburst Tendency of White Sandstone

To explore the tendency of rockburst, a similar material ratio was optimised based on white sandstone. Quartz sand, iron powder, gypsum, cement, retarder, and a water-reducing agent were used as the main materials. The orthogonal test design principle was used to determine the four-factor and four-level orthogonal test design with the quartz sand content, iron powder content, gypsum-cement ratio, and sand particle size as the influencing factors. Uniaxial compression tests and tensile tests were conducted on similar material models. The tensile strength and elastic modulus were analysed, the significance of each influencing factor was investigated, and the test results of the similar materials were fitted. The optimal ratios of the similar materials of white sandstone were found to be quartz sand content of 36%, iron powder content of 1.9%, gypsum-cement ratio of 1.8 : 1, and sand particle size of 2–4 mm. The physical and mechanical properties of the similar materials were consistent with those of white sandstone. The mechanical properties of the similar materials were compared with those of the original rock. By judging the rockburst propensity and verifying the index, it is concluded that the similar materials can effectively simulate the characteristics of white sandstone, which is an ideal similar material of rockburst, and they all show strong rockburst propensity. The rock specimens with optimal proportions were produced, and the internal energy changes and rockburst mechanisms of the model at different temperatures were discussed. The results show that the rockburst process is closely related to energy, such as thermal energy and elastic strain energy, and the rock failure process can be divided into three main stages: energy accumulation, microcrack formation and propagation, and crack penetration and bursting. It provides an experimental basis for the preparation of rockburst similar materials that are more in line with the actual situation of the project and provides a basis for discussing the energy criterion of rockburst.

Olive ridley (Lepidochelys olivacea) laying eggs habitat mapping in Penimbangan Beach, Bali Island

Penimbangan beach is one of the tourist destinations located in Buleleng Regency, Bali Province, Indonesia. This beach is also a nesting place for one of the sea turtle species in Indonesia, which is olive ridley (Lepidochelys olivacea). The problem that exists on the island of Bali today is most of the land in coastal areas were experienced land degradation. This land degradation occurs due to human activities or natural factors, it harms the turtle nesting habitat around the coastal area of Bali Island. Conservation of nesting turtle habitat is needed through spatial analysis using Geographic Information Systems (GIS). This study uses the parameters of sand particle, beach slope, width beach, humidity, and temperature parameter to determine the suitability of the turtle nesting habitat. Penimbangan beach area which is very suitable for turtle nesting locations has an area of 163,45 m2, suitable for laying eggs 4.886,44 m2, and not suitable for laying eggs 10.201,64 m2. The map of the suitability for laying turtle eggs is dominated by areas that are not suitable because the width of the beach is not too long and the humidity is still relatively high.

Efficacy of 3D Dynamic Image Analysis for Characterizing the Morphology of Natural Sands

Two-dimensional Dynamic Image Analysis (DIA) is gaining acceptance in geotechnical engineering research. Three-dimensional (3D) DIA extracts features from 8-12 projections of a particles thus it is believed to verge on the true particle morphology. DIA is fast, efficient, and convenient for characterizing thousands of particles quickly; nevertheless, it captures shapes that are fundamentally different than the 3D morphologies reconstructed using micro-computed tomography (μCT). In DIA particle features are interpreted using external images of a particle, which fail to account for differences in imaging perspectives. In addition, 2D and 3D shape descriptors are influenced by differences in dimensionality projection owing to variations in definition, dimensionality, and perspectives of the particle images employed which causes them to differ from their 3D counterparts. In this study we compared sand particle size and shape descriptors obtained using both DIA and μCT for three natural sands having wide granulometries. 3D DIA offers significant advantages in terms of efficiency, while providing adequate representation of Feret dimensions, Sphericity and Convexity. However, the study demonstrates that 3D Roundness is difficult to characterize using DIA and that shape measurements of complex irregular calcareous sands obtained from 3D DIA are not comparable to those obtained using μCT.

Experimental Study of the Water-Sediment Two-Phase Seepage Characteristics in Rock Fractures and the Influencing Factors

The water-sediment two-phase seepage in coarse fractures is one of the major factors to trigger mine water inrush disasters. Based on seepage mechanics theory, a mechanical model of the water-sediment two-phase seepage in coarse fractures was established. An experimental system was also developed to study the seepage characteristics under various conditions. The relationships between the absolute value of the pressure gradient and the seepage velocity were analyzed during the test process. The nonlinear characteristics of the seepage test were revealed. In addition, variation laws of the absolute value of the pressure gradient with the sand volume fraction and the sand particle size were illustrated, which were related to the loss of pressure during the particle movement. The impacts of the sand volume fraction and the sand particle size on the equivalent fluidity and β -factor of non-Darcy flow were discussed and analyzed. It was determined that the local turbulence was the main reason for the change of nonlinear variation characteristics of seepage parameters.

ECO-Friendly approach in strengthening the different grain size particles by utilizing Sporsarcina pausterii NIOT1

A distinct grain size of 600, 425 and 212 μm sand column was developed to test the efficiency of bacterial strain Sporsarcina pausterii NIOT-1. The bacterial strain was effectively able to precipitate calcite crystals between the soil particles through enzymatic hydrolysis of urea which increases ammonium concentration to the maximum of 371.43 mM, 314.54 mM, 302.49 mM, EC of 98.81 ms/cm, 101.84 ms/cm, 101.34 ms/cm and pH of 8.80, 8.90, 8.80 respectively. The synthesized biomaterials have the maximum UCS of 2400 Mpa with 212 μm grain size followed by 425 and 600 μm with 2200 and 2100 Mpa. Scanning Electron Microscopy and XRD results justify the precipitation of CaCO3 bridging the sand particle. In the study, the maximum UCS attained with fine sand particle size and reduced with the increasing grain size. The current study observed an inverse relationship between grain size and strength. The current green synthesis study also attempts for the feasibility approach to reduce coastal erosion.

Numerical simulation of the effects of sandy water on regulator labyrinth channel in micro-sprinkler systems

The effects of sandy water on the W-shaped labyrinth channel of micro-sprinkler irrigation systems with large flowrate were investigated using Computational Fluid Dynamics (CFD). Using ANSYS FLUENT software and different inflow conditions (e.g., pressure, velocity, sediment concentration, and sand particle diameter), internal turbulent multiphase flow and sand deposition were simulated by the Eulerian multiphase flow model. Particle erosion in the labyrinth channel was calculated by the Discrete Phase Model (DPM). The results show that vortex movements and shear actions at the boundary layer cause self-flushing in the channel. The location of sand particle deposits and the turbulent dissipation rate are related to the operating pressure, which is optimal at 300 kPa. The erosion rate of the channel wall is proportional to the inflow sediment concentration but has no obvious relationship with inflow velocity. Based on the movement regulation of sand particles in the labyrinth channel, recommendations on filtration requirements and operating pressure of irrigation systems are proposed.

Experimental and Computational Investigation of Flow Fields using Accelerated Erosion Test Ring (AETR)

The erosion of the blades of hydraulic pumps and turbines, caused due to the water that has enormous suspended particles and erosive agents, is a severe global challenge among scientists and engineers. In the present work, an attempt has been made to compute the extent of erosion caused by water when it passes through devices like hydraulic machines, centrifugal pumps and turbines. Experimental and computational techniques using pitched turbine blades with 45o with the horizontal plane under down pumping condition is employed for investigation of the suspension phenomena for calculating erosion wear by sand suspended in water in river, canal on turbine, pump blades. An experimental set up, named as Accelerated Erosion Test Rig (AETR), is developed through dimensional analysis. For experimental analysis, the sand particle size and propeller dimensions were varied while running the propeller at different speeds. Experimental results revealed that the propeller speed must be maintained at an optimum value, preferably lower speeds, to ensure maximum lifting of impurities and sand particles from the base of the cylinder.

Investigation of the material mixtures and fiber addition for 3D concrete printing

The era of Construction 4.0 is characterized by technological advances used in the construction industry. One of the advancements is the use of 3D concrete printing in construction. However, until now, the development of 3D concrete printing in Indonesia is still minimal. The main challenge is to determine the composition of the material mixtures for making the mortar, having good extrudability but still has sufficient strength. The rapid initial setting time required was also different for the concrete for typical construction. Our previous mixture composition incorporating calcium oxide to accelerate the initial setting time was adequate. However, the extrusion process was still not satisfactory. In this study, the effect of cement to sand ratio, sand particle size, and the addition of synthetic micro-fiber was investigated on the main properties of 3D printing materials, i.e., initial setting time, flowability, extrudability, and compressive strength. It was found that using smaller maximum particle size sand increases the initial setting time. The addition of synthetic microfiber reduces the strength and the workability of the mortar. However, fiber inclusion has advantages as it reduces the possibility of cracking in the printed concrete. The extruded concrete specimens were shown to have significant strength reduction due to lack of compaction, and it was affected by the direction of printing showing orthotropic properties of the 3D printed concrete.