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

Abstract

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.

IoT-Based Geotechnical Monitoring of Unstable Slopes for Landslide Early Warning in the Darjeeling Himalayas

“…Inclinometers can also be used for deep-seated installations [34] but cannot be chosen for low-cost installation in large areas due to the expense and expertise required for installation. Usage of several wireless sensors are reported in the literature for monitoring landslides [35][36][37][38][39][40][41], and in this study, a more reliable approach is attempted by using tilt sensors [38,42], which are found to be an economically viable solution.…”

Physical Model Experiments on Water Infiltration and Failure Modes in Multi-Layered Slopes under Heavy Rainfall

“…It should be noted that in multi-layer slopes, different geometric characteristics, such as different heights, slope ratios, and fronts, also have an influence on the water infiltration and water content distribution in the slopes, significantly affecting slope failure initiation. Model experiments with different geometries of the shallow soil cover will be conducted in further research [39].…”

Experimental Hazardous Rock Block Stability Assessment Based on Vibration Feature Parameters

“…Advances in Civil Engineering (microelectromechanical accelerometer, electromagnetic vibration exciter, LDV, etc.) [21,30,33], more studies are focusing on vibration feature parameters to monitor geotechnical slope. According to equation ( 3), there are quantitative relations between the natural frequency characteristics of rock blocks and their stiffness, while Figure 9 shows that there is a good correlation between five frequency-domain parameters and the safety factor of the rock block.…”