A new geotechnical method for natural slope exploration and analysis

Abstract

Geotechnical investigation of natural slopes is challengeable especially when natural slopes having higher gradients and access is difficult. Also, it is even more problematic to find the shear strength parameters spatially to evaluate the stability of slopes as most of the methods available to find the shear strength parameters in the literature are uneconomical or such methods cannot be applied in vegetated slopes. Recently, authors have conducted a series of in situ investigations based on the newly developed lightweight dynamic cone penetrometer to examine its applicability in analyzing the slopes covered with weathering remnants of decomposed granite. Six patterns were identified based on the penetration resistance varies with the depth. Spatial variability analysis conducted on different grid spaces showed that the coefficient of variation of cone resistance varies from 0 to 35 %. Semi-variogram analysis showed that the Spherical Models can be used to evaluate the spatial variability of weathering remnants of decomposed granite. A series of laboratory calibration tests based on the lightweight dynamic cone penetration tests and direct shear tests with pore pressure measurements were conducted at different void ratios and degrees of saturation. Based on the laboratory calibration test results, a method to determine the void ratio, e, from the data of q d was presented. Based on this, two formulas to evaluate the shear strength parameters, apparent cohesion and friction angle, were established with the cone resistance and degree of saturation. Slight modification was proposed in evaluating the apparent cohesion with respect to the different fine content in the soils. As a whole, the proposed method can be successfully applied to individual slopes to determine the profile thickness and to evaluate the shear strength parameters spatially. Based on this, hazard assessment of individual slopes can be made.

Toward improved prediction of the bedrock depth underneath hillslopes: Bayesian inference of the bottom‐up control hypothesis using high‐resolution topographic data

“…Research into measurement methods has led to the development and use of direct and indirect sensing techniques to determine the bedrock depth at point and larger support. Examples of direct measurement methods include rod penetrometers [ Kuriakose et al ., ; Tesfa et al ., ; Fu et al ., ; Lanni et al ., ; Lucà et al ., ], excavated pits [ Boer et al ., ; Heimsath et al ., ; Pelletier and Rasmussen , ; Catani et al ., ; Pelletier et al ., ], hand and gasoline or electric‐powered augers [ Fernandes et al ., ; Ziadat , ; Liu et al ., ], road cuts, and erosion gullies [ Kuriakose et al ., ; Wilford and Thomas , ], and dynamic cone penetrometers [ Kosugi et al ., ; Fujimoto et al ., ; Ohnuki et al ., ; Tsuchida et al ., ; Askarinejad et al ., ; Wiegand et al ., ; Athapaththu et al ., ; Liang and Uchida , ]. This last measurement device is particularly promising as it can help delineate soil stratigraphy and layers with contrasting hydraulic properties [ Eguchi et al ., ; Masaoka et al ., ].…”

Geotechnical Assessment of Natural Slopes and Valleys Based on Real Time Rainfall Data

“…A same methodology which was adopted for weathered Granite (ex. [6], [8]) was used when carrying out the tests for weathered Rhyolite. Calibration tests were conducted for the void ratios ranging from 0.7 to 1.1 in 0.1 intervals and degrees of saturation ranging from 40% to 80% in 10% increments.…”

“…A typical procedure for the investigation of natural slope was established based on the previous studies carried out and is available the literature published by Athapaththu et al [8]. The procedure with slight modifications is as follows.…”

“…(8) Where, cd, is the cohesion , ϕd is the friction angle , H is the thickness of the soil layer, hw is the height of water table, γsat is the saturated unit weight , γt is the unit weight of water, and β is the slope angle.…”

“…The detailed information of the procedure and outcomes are available in the literature published by Tsuchida et al [6], [7], and Athapaththu et. al [8], [9].…”