scholarly journals Evaluation of Soil Moisture and Shear Deformation Based on Compression Wave Velocities in a Shallow Slope Surface Layer

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3406 ◽  
Author(s):  
Shangning Tao ◽  
Taro Uchimura ◽  
Makoto Fukuhara ◽  
Junfeng Tang ◽  
Yulong Chen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Surface Layer ◽  
Soil Moisture ◽  
Wave Velocity ◽  
Early Warning System ◽  
Slope Failure ◽  
Velocity Ratio ◽  
Warning System ◽  
Slope Surface ◽  
Wave Velocities

Rainfall-induced landslides occur commonly in mountainous areas around the world and cause severe human and infrastructural damage. An early warning system can help people safely escape from a dangerous area and is an economical and effective method to prevent and mitigate rainfall-induced landslides. This paper proposes a method to evaluate soil moisture and shear deformation by compression wave velocities in a shallow slope surface layer. A new type of exciter and new receivers have been developed using a combination of micro electro-mechanical systems (MEMS) accelerometers and the Akaike’s information criterion (AIC) algorithm, which can automatically calculate the elastic wave travel time with accuracy and reliability. Laboratory experiments using a multi-layer shear model were conducted to reproduce the slope failure. The relationships between wave velocities and soil moisture were found to be dependent on the saturation path (rain or drain); in other words, hysteresis was observed. The wave velocity ratio reduced by 0.1–0.2 when the volumetric water content (VWC) increased from 0.1 to 0.27 m3/m3. When loading the shear stress corresponding to slope angles of 24, 27, 29, or 31 degrees, a drop of 0.2–0.3 in wave velocity ratio was observed at the middle layer, and near 0.5 at the bottom layer. After setting the shear stress to correspond to a slope angle of 33 degrees, the displacement started increasing and finally, slope failure occurred. With increasing displacement, the wave velocities also decreased rapidly. The wave velocity ratio dropped by 0.2 after a displacement of 3 mm. Monitoring long-term elastic wave velocities in a slope surface layer allows one to observe the behavior of the slope, understand its stability, and then apply an early warning system to predict slope failure.

Landwarn: An Operative Early Warning System for Landslides Forecasting Based on Rainfall Thresholds and Soil Moisture

2013 ◽  
pp. 627-634 ◽  
Author(s):  
Francesco Ponziani ◽  
Nicola Berni ◽  
Marco Stelluti ◽  
Renato Zauri ◽  
Claudia Pandolfo ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Early Warning ◽  
Early Warning System ◽  
Warning System ◽  
Rainfall Thresholds

Research and Application of Phase Space Reconstruction Theory in the Prediction of Slope Failure

2013 ◽  
Vol 734-737 ◽  
pp. 791-795 ◽  
Author(s):  
Chuang Ye Wang ◽  
Hong Guang Ji ◽  
Wan Dong Han
Keyword(s):  
Phase Space ◽  
Predictive Model ◽  
Early Warning System ◽  
Prediction Error ◽  
Slope Failure ◽  
Warning System ◽  
Phase Space Reconstruction ◽  
Time Sequence ◽  
Evaluation Index System ◽  
Error Method

The research of slope failure, which is one of the main types of natural disasters, has become a hot topic. Effective landslide forecast can improve the early warning system of landslides and mitigate the landslide disasters. In this paper, a predictive model with the slopes displacement time sequence is established based on the phase space reconstruction theory, where the parameter of the predictive model is obtained by the minimum of prediction error method. The rationality of the evaluation index system is verified through the case studies.

scholarly journals Brief communication: Using averaged soil moisture estimates to improve the performances of a regional-scale landslide early warning system

2018 ◽  
Vol 18 (3) ◽  
pp. 807-812 ◽  
Author(s):  
Samuele Segoni ◽  
Ascanio Rosi ◽  
Daniela Lagomarsino ◽  
Riccardo Fanti ◽  
Nicola Casagli
Keyword(s):  
Soil Moisture ◽  
Early Warning ◽  
Early Warning System ◽  
Preliminary Investigation ◽  
Regional Scale ◽  
Back Analysis ◽  
Warning System ◽  
False Alarms ◽  
Rainfall Thresholds ◽  
Landslide Early Warning

Abstract. We communicate the results of a preliminary investigation aimed at improving a state-of-the-art RSLEWS (regional-scale landslide early warning system) based on rainfall thresholds by integrating mean soil moisture values averaged over the territorial units of the system. We tested two approaches. The simplest can be easily applied to improve other RSLEWS: it is based on a soil moisture threshold value under which rainfall thresholds are not used because landslides are not expected to occur. Another approach deeply modifies the original RSLEWS: thresholds based on antecedent rainfall accumulated over long periods are substituted with soil moisture thresholds. A back analysis demonstrated that both approaches consistently reduced false alarms, while the second approach reduced missed alarms as well.

P-to-S-wave velocity ratio in organic shales

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. MR205-MR222 ◽  
Author(s):  
Sheyore John Omovie ◽  
John P. Castagna
Keyword(s):  
Wave Velocity ◽  
Pore Space ◽  
Velocity Ratio ◽  
Organic Content ◽  
Theoretical Modeling ◽  
S Wave ◽  
Lower Velocity ◽  
Wave Velocities ◽  
Ultrasonic Measurements

In situ P- and S-wave velocity measurements in a variety of organic-rich shales exhibit P-to-S-wave velocity ratios that are significantly lower than lithologically similar fully brine-saturated shales having low organic content. It has been hypothesized that this drop could be explained by the direct influence of kerogen on the rock frame and/or by the presence of free hydrocarbons in the pore space. The correlation of hydrocarbon saturation with total organic content in situ makes it difficult to separate these possible mechanisms using log data alone. Theoretical bounding equations, using pure kerogen as an end-member component without associated gas, indicate that kerogen reduces the P- and S-wave velocities but does not in general reduce their ratio enough to explain the observed low velocity ratio. The theoretical modeling is consistent with ultrasonic measurements on organic shale core samples that indicate no dependence of velocity ratios on the kerogen volume alone. Sonic log measurements of P- and S-wave velocities in seven organic-rich shale formations deviate significantly (typically more than 5%) from the Greenberg-Castagna empirical brine-saturated shale trend toward lower velocity ratios. In these formations, and on core measurements, Gassmann fluid substitution to 100% brine saturation yields velocity ratios consistent with the Greenberg-Castagna velocity trend for fully brine-saturated shales, despite the high organic content. These sonic and ultrasonic measurements, as well as theoretical modeling, suggest that the velocity ratio reduction in organic shales is best explained by the presence of free hydrocarbons.

scholarly journals Strength Analysis and Assessment of Ina-TEWS Wave Glider

2020 ◽  
Vol 4 (3) ◽  
pp. 140
Author(s):  
Kusnindar Priohutomo ◽  
Wibowo Harso Nugroho ◽  
Rosi Dwi Yulfani
Keyword(s):  
Shear Stress ◽  
Maximum Principle ◽  
Early Warning System ◽  
Structural Strength ◽  
Warning System ◽  
Strength Analysis ◽  
Mooring System ◽  
Wave Glider ◽  
Fiberglass Material ◽  
Eva Foam

Indonesia as a country that often experiences tsunami disasters needs to have an early warning system against tsunami disasters. This system can use various existing technologies, one of which is the tsunami buoy system. The new tsunami buoy system does not use the natural mooring system but uses the wave glider system. This paper discusses the structural strength of the surface floater of wave glider using Eva Foam and Fiberglass material for skin and Alluminium material for frame and kell. The surface floater using 16 pieces for frame and 1 piece for keel. Enviromental loads is use in this paper like hydrodynamics load and weight load. The results from this paper is material from Eva Foam has a maximum principle stress is 12693 Pa and shear stress is 6114.6 Pa. For material from Fiberglass has maximum principle stress is 11.875 Pa and shear stress is 6076.3 Pa. Safety factor (SF) from maximum principle stress and shear stress for Eva Foams is up to 6x and SF for maximum principle and shear stress for Fiberglass is up to 26x. Conclusions for this paper is the desain for surface floater of wave glider it can be operated in the sea with draugh 0.18 m.

scholarly journals Experimental Study on Petrophysical Properties as a Tool to Identify Pore Fluids in Tight-Rock Reservoirs

2021 ◽  
Vol 9 ◽  
Author(s):  
Rupeng Ma ◽  
Jing Ba ◽  
José Carcione ◽  
Maxim Lebedev ◽  
Changsheng Wang
Keyword(s):  
Wave Velocity ◽  
Poisson’S Ratio ◽  
Velocity Ratio ◽  
Data Distribution ◽  
Poisson's Ratio ◽  
Petrophysical Properties ◽  
Pore Fluids ◽  
S Wave ◽  
Wave Velocities ◽  
Lame Constant

The petrophysical properties can be proper indicators to identify oil and gas reservoirs, since the pore fluids have significant effects on the wave response. We have performed ultrasonic measurements on two sets of tight siltstones and dolomites at partial saturation. P- and S-wave velocities are obtained by the pulse transmission technique, while attenuation is calculated using the centroid-frequency shift and spectral-ratio methods. The fluid sensitivities of different properties (i.e., P- and S-wave velocities, impedances and attenuation, Poisson's ratio, density, and their combinations) are quantitatively analyzed by considering the data distribution, based on the crossplot technique. The result shows that the properties (P- to S-wave velocity and attenuation ratios, Poisson's ratio, and first to second Lamé constant ratio) with high fluid-sensitivity indicators successfully distinguish gas from oil and water, unlike oil from water. Moreover, siltstones and dolomites can be identified on the basis of data distribution areas. Ultrasonic rock-physics templates of the P- to S-wave velocity ratio vs. the product of first Lamé constant with density obtained with a poroelastic model, considering the structural heterogeneity and patchy saturation, are used to predict the saturation and porosity, which are in good agreement with the experimental data at different porosity ranges.

scholarly journals An Experimental Study of Velocity-Saturation Relationships in Volcanic Rocks

2015 ◽  
Vol 8 (1) ◽  
pp. 142-152 ◽  
Author(s):  
Zhidi Liu ◽  
Jingzhou Zhao
Keyword(s):  
Wave Velocity ◽  
Water Saturation ◽  
Velocity Ratio ◽  
Volcanic Rocks ◽  
Junggar Basin ◽  
S Wave ◽  
Gas Reservoirs ◽  
Velocity Saturation ◽  
Wave Velocities ◽  
Water Saturated

In this paper, experiments are carried out under different pressures and water saturations using core samples of volcanic rocks from the Junggar Basin in China to understand how water saturation affects P- and S-wave velocities. The results show that water saturated rocks exhibit significantly higher P- and S-wave velocities than gas saturated rocks. In addition, the P- and S-wave velocity ratio declines with increasing water saturation. Furthermore, a P- and S-wave velocity ratio vs. resistivity cross plot is created to identify gas reservoirs in the volcanic rocks in the Junggar Basin.

scholarly journals Brief communication: Using punctual soil moisture estimates to improve the performances of a regional scale landslide early warning system

2017 ◽  
Author(s):  
Samuele Segoni ◽  
Ascanio Rosi ◽  
Daniela Lagomarsino ◽  
Riccardo Fanti ◽  
Nicola Casagli
Keyword(s):  
Soil Moisture ◽  
Early Warning ◽  
Early Warning System ◽  
Regional Scale ◽  
Back Analysis ◽  
Warning System ◽  
Threshold Value ◽  
False Alarms ◽  
Rainfall Thresholds ◽  
Landslide Early Warning

Abstract. We improved a state-of-art RSLEWS (regional scale landslide early warning system) based on rainfall thresholds by integrating punctual soil moisture estimates. We tested two approaches. The simplest can be easily applied to improve other RSLEWS: it is based on a soil moisture threshold value under which rainfall thresholds are not used because landslides are never expected to occur. Another approach deeply modifies the original RSLEWS: thresholds based on antecedent rainfall accumulated over long periods were substituted by soil moisture thresholds. A back analysis demonstrated that both approaches reduced consistently false alarms, while the second approach reduced missed alarms as well.

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