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Urban Geologic Mapping
Published in Daniel T. Rogers, Urban Watersheds, 2020
After examining the depositional layers from excavation pits as shown in Figure 5.4, evaluating and recording the strike and dip of the depositional units is required before a three-dimensional map can be developed (Lahee 1961). Strike refers to the attitude or trend of a particular deposit. For instance, if a geologist were mapping a sandy beach deposit from an ancient lake and recorded the trend of the deposit at several locations, the geologist would be able to determine the size of the lake. The Strike of a deposit, outcrop, or other planar feature is represented on a geologic map as a short straight-line segment oriented parallel to the compass direction of the strike. The dip is defined as the angle at which the geologic deposit, feature, or structure is tilted relative to the horizontal plane. The dip is represented on map as a line segment perpendicularly attached to the strike symbol.
Model testing and photo-elasticity in rock mechanics
Published in Ömer Aydan, Rock Mechanics and Rock Engineering, 2019
Figure 5.7 shows that a series of experiments were carried out on rock slope models with breakable material under a thrust faulting action with an inclination of 5.5 degrees. When layers dip toward valley side, the ground surface is tilted, and the slope surface becomes particularly steeper. As for layers dipping into the mountain side, the slope may become unstable, and flexural or columnar toppling failure occurs. Although the experiments are still insufficient to draw conclusions, they do show that discontinuity orientation has great effects on the overall stability of slopes in relation to faulting mode. These experiments clearly show that the forced displacement field induced by faulting has an additional destructive effect besides ground shaking on the stability of slopes.
Geological Maps
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
The strike of a surface is the direction of a horizontal line drawn at 90° to the direction of true dip. The direction N 120° (or N 300°) is the strike of the surface shown in Fig. 12.10 as is the direction of the line A′B′ in Fig. 12.12b. Because of its horizontality a line drawn in the direction of strike is equivalent to an elevation contour for the surface. Figure 12.13 illustrates how the strike directions of a planar surface can be extended to produce strike lines which are also contours for the surface and are called structural contours. However, the majority of geological surfaces are not planar and the unlimited extension of strike lines away from the points at which dip and strike are measured can result in incorrect predictions.
Comparison and analysis of different methods for structural planes measuring in underground roadways
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Hongdi Jing, Xiaobo Liu, Anlin Shao, Liancheng Wang
The dip angle of rock layer refers to the angle between the rock layer and the horizontal plane, which is always perpendicular to the rock strike. When measuring, the upper part of the compass is placed close to the rock layer, and the lower part of the compass is kept horizontal. At this time, the value indicated by the compass is the dip angle of the rock layer.
GIS-based soil planar slide susceptibility mapping using logistic regression and neural networks: a typical red mudstone area in southwest China
Published in Geomatics, Natural Hazards and Risk, 2021
Shuai Zhang, Can Li, Jingyu Peng, Dalei Peng, Qiang Xu, Qun Zhang, Bate Bate
The topological attributes, such as elevation, slope angle, slope aspect, slope structure, and curvature, are derived from the digital elevation method (DEM) with a resolution of 30 m. These are generated from a triangulated irregular network (TIN) model. As shown in Fig. 8b, the potential soil planar slides in the study area are mainly located between elevations of 500 m and 1000 m. The soil planar slides in the red layer area of Nanjiang are mainly distributed within the elevation range of 230–1500 m, and especially between 500–1000 m. According to the statistics, the elevation of the soil planar slides follows a normal distribution. The landslide densities in elevations of 230–500 m, 500–1000 m and greater than 1000 m are 0.63 landslides/km2, 0.68 landslides/km2, and 0.20 landslide/km2, respectively (Fig. 9b). It can be found that not only does the slope structure at the elevation of 500–1000 m is mainly monoclinic, making it easy for a landslide to occur, but it is also due to intense human activities, including cropland irrigation and engineering excavations. These human activities are concentrated mainly within the same range of elevation, which further reduces the stability of the slope. As shown in Fig. 8c, the density points of landslides with a slope angle smaller than 10°, between 10°–30°, and larger than 30° are 0.542, 0.664, and 0.346 landslides/km2, respectively. Soil planar slides are normally distributed in the monoclinic region within the range of 10°–30°. Rainwater can gather and penetrate the surface of the gentle slopes easily. Moreover, the dip-direction of the bedding slope is consistent with the inclination direction, which leads to the occurrence of bedding failures along with the soil-bedrock interface. Local human activities and land use within the affected area can accelerate the occurrence of landslides. Furthermore, the soil planar slides are evenly distributed at different slope aspects in the red mudstone area of Nanjiang, where landslides in the directions of 90°–180° and 270°–360° are the most accounted for (Fig. 9d). The majority of the soil planar slides are distributed in dip slopes with a density of 0.5926 landslides/km2, followed by oblique slopes with a density of 0.5811 landslides/km2, and anti-dip slopes of 0.5515 landslides/km2 (Fig. 9e). The dip slopes are prone to landslides due to the underlying dipping strata. Large sheets of rock tend to slide down the dip slopes, whereas for anti-dip slopes, the effect is the opposite.