Effects of an impermeable layer on pore pressure response to tsunami-like inundation

Tsunami hazards have been observed to cause soil instability resulting in substantial damage to coastal infrastructure. Studying this problem is difficult owing to tsunamis’ transient, non-uniform and large loading characteristics. To create realistic tsunami conditions in a laboratory environment, we control the body force using a centrifuge facility. With an apparatus specifically designed to mimic tsunami inundation in a scaled-down model, we examine the effects of an embedded impermeable layer on soil instability: the impermeable layer represents a man-made pavement, a building foundation, a clay layer and alike. The results reveal that the effective vertical soil stress is substantially reduced at the underside of the impermeable layer. During the sudden runup flow, this instability is caused by a combination of temporal dislocation of soil grains and an increase in pore pressure under the impermeable layer. The instability during the drawdown phase is caused by the development of excess pore-pressure gradients, and the presence of the impermeable layer substantially enhances the pressure gradients leading to greater soil instability. The laboratory results demonstrate that the presence of an impermeable layer plays an important role in weakening the soil resistance under tsunami-like rapid runup and drawdown processes.

Understanding Mud Volcano System Using Hele-Shaw (H-S) Experiment: Seismic Confirmation at East Java Mud Volcano

Numerous researchers have carried out studies on the mud volcano system in East Java. However, there have been no experiments on the mud volcano system's mechanism, including overpressure confirmed by direct subsurface data. Therefore, this study aims to directly evaluate the mud volcano system's mechanism using the Hele-Shaw (H-S) experiment with the subsurface data confirmation. The H-S experiment utilized four primary materials: quartz sand diameter below 250 µm and 320 µm to analogize the porous layer. Gypsum flour clay is the ductile layer, while mud from the Kuwu and Kesongo Mud Volcanoes is the original material from nature. Wax represents impermeable material. The sealing layer is made of wax, and oxygen represents the natural fluids of the rock formation. The overpressured zone is created by pumping oxygen into a layer of quartz sand covered by a wax as an impermeable layer. Pressure is measured digitally, and the process is continuously recorded to produce traceable data. Each material was experimented on individually to determine the critical phase characteristics, valve fault structure geometry, and validation with seismic interpretation. The results indicate that the critical phase of the mud volcano system is characterized by the dome structure at the surface, with high intensify of gas and oil seepage. Piercement structure geometry is shown by plumbing of fluidization zone, which becomes shallower than before. Furthermore, each material's piercement structure geometry shows a consistent pattern, with differences in the density of the fault and pressure structures. Thus, the H-S experiment's validation with seismic interpretation shows a similar geometry in pressure structures and valve faults as the mud volcano system's migration paths.

Toprak Hidrolik İletkenlik Ölçümünün Atölye Koşullarında Modellenmesi

The aim of this study is to model the system that measures soil hydraulic conductivity using Programmable Logic Control (PLC), pressure transducer and motor pump in workshop conditions. In the study, a plastic pipe with a length of 2 m and a diameter of 100 was prepared to simulate an auger hole. In addition, a set was created using PLC and its module. In the hydraulic conductivity measurement system, the auger hole method (the bottom of the auger hole is above the impermeable layer) is used. Using the auger-hole equation, the system’s program was written in CODESYS-ST language and uploaded to the PLC. As a result of the regression analysis between the water head in the pipe (auger-hole) measured by hand (ESY) and PLC (PLCSY), an equation as PLCSY = 0,99ESY + 1,69 (R² = 1) was obtained and the Mean Absolute Percent Error (MAPE) of these two data sets was calculated as 0,41%. Each hydraulic conductivity measurement time is approximately 5, 6 and 8 minutes when the valve is fully open and half open and one-third open. The distance from the pipe base to the static level (d, cm) was measured as averages of 122.83, 123.91 and 123.7 cm on, respectively. In the first quarter section, the average times taken for the water level to rise from 20 to 25, 25 to 30, 30 to 35 and 35 to 40 was determined as 4.4, 6.0 and 26.1 seconds, respectively. The hydraulic conductivity values were calculated as 18.6, 13.2 and 3.1 cm/hour at the valve openings, respectively. The measured data is saved on an SD card. All of these processes are done automatically. The expectation that this system will measure hydraulic conductivity accurately, economically and quickly in field conditions is high and should be tested in field conditions.

Sand- and Clay-Photocured-Geomembrane Interface Shear Characteristics Using Direct Shear Test

It is well known that geomembranes frequently and easily fail at the seams, which has been a ubiquitous problem in various applications. To avoid the failure of geomembrane at the seams, photocuring was carried out with 1~5% photoinitiator and 2% carbon black powder. This geomembrane can be sprayed and cured on the soil surface. The obtained geomembrane was then used as a barrier, separator, or reinforcement. In this study, the direct shear tests were carried out with the aim to investigate the interfacial characteristics of photocured geomembrane–clay/sand. The results show that a 2% photoinitiator has a significant effect on the impermeable layer for the photocured geomembrane–clay interface. As for the photocured geomembrane–sand interface, it is reasonable to choose a geomembrane made from a 4% photoinitiator at the boundary of the drainage layer and the impermeable layer in the landfill. In the cover system, it is reasonable to choose a 5% photoinitiator geomembrane. Moreover, as for the interface between the photocurable geomembrane and clay/sand, the friction coefficient increases initially and decreases afterward with the increase of normal stress. Furthermore, the friction angle of the interface between photocurable geomembrane and sand is larger than that of the photocurable geomembrane–clay interface. In other words, the interface between photocurable geomembrane and sand has better shear and tensile crack resistance.

Gas flow permeability and gas pressures in stilt roots of Red Mangrove (Rhizophora mangle L.)

The Red Mangrove (Rhizophora mangle) is typically rooted in anoxic mud conditions that require special adaptations for root oxygenation. Each plant has multiple "stilt roots" that descend from upper branches and end in roots buried the mud. In cross section each stilt root consists of a core of porous aerenchyma surrounded by an impermeable layer of xylem, and outside the xylem there is a second layer aerenchyma. Oxygen must be provided to the mud roots through the aerenchyma either by diffusion or by gas flow, where the separate layers could provide up- and down-flow pathways. To test whether the stilt root's properties were consistent with gas flow, conductivities were measured. A technique was developed that measured flow conductivities in S.I. scientific units without using a flow meter and a calibrated pressure gauge. The core aerenchyma was more permeable to gas flow than any other plant tissue, except for those stems that are hollow tubes. Because there was little lateral leakage from the core aerenchyma, it had pipe-like properties. In the outer aerenchyma gas conductivity was high, and gas flowed easily through large lenticels on the surface of the stilt root. To complete the calculations, gas pressures in the stilt roots were measured. The calculated gas flow rates through mud roots was not sufficient to supply O2 for root respiration, suggesting that diffusion may be the more important mechanism for these plants.

Performing calculus: Asymmetric adaptive stimuli-responsive material for derivative control

Materials (e.g., brick or wood) are generally perceived as unintelligent. Even the highly researched “smart” materials are only capable of extremely primitive analytical functions (e.g., simple logical operations). Here, a material is shown to have the ability to perform (i.e., without a computer), an advanced mathematical operation in calculus: the temporal derivative. It consists of a stimuli-responsive material coated asymmetrically with an adaptive impermeable layer. Its ability to analyze the derivative is shown by experiments, numerical modeling, and theory (i.e., scaling between derivative and response). This class of freestanding stimuli-responsive materials is demonstrated to serve effectively as a derivative controller for controlled delivery and self-regulation. Its fast response realizes the same designed functionality and efficiency as complex industrial derivative controllers widely used in manufacturing. These results illustrate the possibility to associate specifically designed materials directly with higher concepts of mathematics for the development of “intelligent” material-based systems.

Determining Groundwater Potential Using Vertical Electrical Sounding Method In Manggar, Balikpapan City, Indonesia.

Clean water requirement in Manggar Urban Village of Balikpapan City is rising along with population growth. The main source of clean water that can be used is ground water in the aquifer layer. The Study of groundwater potential was conducted using vertical electrical sounding (VES) method to determine the presence and types of aquifer layers. The measurements along four measurement points revealed four aquifers buried in depth ranging from 48 to 53 m below the surface. The layer which is potential to be an aquifer is a sand layer with moderate-sized grain. The resistivity values for sand layer at each measurement point vary from 221 to 281Ωm. The estimation of sand to be an aquifer layer was supported by the calculation of formation factors. The calculation was based on the ratio of resistivity values from pore-filling water and resistivity values from water-saturated rocks layer. The aquifer revealed in this study is categorized as unconfined aquifer because the upper layer is restricted by sandy clay. The resistivity values vary from 12.8 to 35.4 Ωm which behaved as an aquitard layer. However, low resistivity values between 9.6 to 20 Ωm are detected under the aquifer layer. The layer is identified as clay which behaved as an impermeable layer or aquiclude.

Landside tritium leakage over through years from Fukushima Dai-ichi nuclear plant and relationship between countermeasures and contaminated water

There has been tritium groundwater leakage to the land side of Fukushima Dai-ichi nuclear power plants since 2013. Groundwater was continuously collected from the end of 2013 to 2019, with an average tritium concentration of approximately 20 Bq/L. Based on tritium data published by Tokyo Electric Power Company Holdings (TEPCO) (17,000 points), the postulated source of the leakage was (1) leaks from a contaminated water tank that occurred from 2013 to 2014, or (2) a leak of tritium that had spread widely over an impermeable layer under the site. Based on our results, sea side and land side tritium leakage monitoring systems should be strengthened.