Study on the Deformation of Filling Bodies in a Loess Mountainous Area Based on InSAR and Monitoring Equipment

Several land-creation projects, such as the Lanzhou New Area (LNA), have been undertaken in China as part of the Belt and Road Initiative to bring more living space to the local people in loess areas. However, undisturbed loess and remolded loess have different mechanical characteristics, which may influence the stability of the filling process. Therefore, we monitored the deformation through InSAR and field monitoring to investigate the deformation characteristics and their causes. We obtained the horizontal and vertical displacements, internal deformation, water content, and pressure, according to the air–space–ground integrated monitoring technique. The results show that stress and deformation increase rapidly during construction. Deformation in different places is different during the winter: (1) for vertical displacement, uplift is present in the cut area, settlement is present in the fill area, and heterogeneity is evident in other areas; (2) for horizontal displacement, the expansion state is present in the filling area and the compression state is present at the boundary. Laboratory tests show that the difference in soil compression properties is one of the reasons for these deformation characteristics. Additionally, the difference in volumetric water content and permeability coefficient may trigger different mechanical properties on both sides of the boundary. All the evidence indicates that the boundary region is critical for filling projects. It is also necessary to install monitoring equipment to observe deformation. When abnormal deformations appear, we should take measures to control them

Integration of Spatial Probability and Size in Slope-Unit-Based Landslide Susceptibility Assessment: A Case Study

Landslide spatial probability and size are two essential components of landslide susceptibility. However, in existing slope-unit-based landslide susceptibility assessment methods, landslide size has not been explicitly considered. This paper developed a novel slope-unit based approach for landslide susceptibility assessment that explicitly incorporates landslide size. This novel approach integrates the predicted occurrence probability (spatial probability) of landslides and predicted size (area) of potential landslides for a slope-unit to obtain a landslide susceptibility value for that slope-unit. The results of a case study showed that, from a quantitative point of view, integrating spatial probability and size in slope-unit-based landslide susceptibility assessment can bring remarkable increases of AUC (Area under the ROC curve) values. For slope-unit-based scenarios using the logistic regression method and the neural network method, the average increase of AUC brought by incorporating landslide size is up to 0.0627 and 0.0606, respectively. Slope-unit-based landslide susceptibility models incorporating landslide size had utilized the spatial extent information of historical landslides, which was dropped in models not incorporating landslide size, and therefore can make potential improvements. Nevertheless, additional case studies are still needed to further evaluate the applicability of the proposed approach

A numerical study on artificial fill embankment with liquefiable foundation using FLAC

The problem of seismic liquefaction related to artificial fill embankment is complicated. In this study, by making using of Finn model, a typical artificial fill embankment was simulated by means of Finn model in FLAC. Numerical simulation results indicated that the pore water pressure of saturated sand soil increased extremely which resulted in the significant decrease of the effective stress. When the effective stress decreased approximately to zero, the liquefaction phenomena occurred. According to the change of pore water pressure at different locations and depths, three rules have been obtained. Firstly, the occurrence time for the first peak of pore water pressure coincided with the seismic peak acceleration of input wave. Secondly, the liquefaction occurred earlier in the upper layer of saturated sand soil than in the lower layer below the bottom of slope. However the duration of liquefaction in the lower layer of saturated sand soil was longer than in the upper layer. Thirdly, the upper layer of saturated sand soil was almost not liquefiable below the top of slope, while the lower layer was easily liquefiable with long duration time. In summary, the characteristics of seismic liquefaction in the artificial fill embankment were closely related to the seismic wave, locations and depths of saturated sand soil in a slope. 2013 American Society of Civil Engineers

Laboratory Investigation of the Mechanical Properties of a Rubber–Calcareous Sand Mixture: The Effect of Rubber Content

This paper introduces a rubber–calcareous sand mixture as a lightweight building material in offshore engineering. The mechanical properties of mixtures of varying rubber contents were investigated by performing a one-dimensional (1-D) compression test in a modified oedometer cell, as well as a resonant column test. A discussion on the test results, along with detailed interpretations regarding the role of rubber chips in the mixtures, are provided. It was found that the virgin compression curves of the rubber–calcareous sand mixtures tended to converge at a certain stress level, whilst the stress level depended on the rubber content. Moreover, the relative breakage was examined by comparing the particle size distribution curves of the calcareous sand before and after the compression test. It was shown that the grain crushing of calcareous sand was less remarkable with the inclusion of rubber chips. Furthermore, the small strain shear modulus (G0) of the mixtures decreased with the rubber content, yet the modulus reduction and damping curves exhibited little difference for the specimens of varying rubber contents

Comparisons of Dynamic Landslide Models on GIS Platforms

Numerical simulation is one of the methods to assess landslide movement processes, which is beneficial for engineering design and urban planning. With the development of computer technology, GIS has gradually become the mainstream platform for landslide simulation due to data availability and algorithm integrability. However, the dynamic processes of landslides are complicated, which makes integration difficult on GIS platforms. Some assumptions are applied to simplify these dynamic processes and solve this problem. Generally, there are two main types of numerical models on GIS platforms: models based on the Eulerian description and models based on the Lagrangian description. Case studies show that Eulerian models are suitable for flow-like movement, and Lagrangian models are suitable for discrete rigid bodies movement. Different models face different problems: the Eulerian-based models show numerical diffusion and oscillation, and the Lagrangian-based model needs to consider complicated shear and collision processes. In addition, the 3-D model can describe more details in the z-direction, while the depth-averaged model can obtain a reasonable range of motion, depth, and speed quickly. From the view of numerical simulation, inappropriate models, assumptions, and numerical schemes will produce errors. The landslide type refers to several forms of mass wasting associated with a wide range of ground movements, which guides establishing dynamic models and numerical schemes on GIS platforms and helps us obtain results accurately

River centerline extraction using the multiple direction integration algorithm for mixed and pure water pixels

The river centerline is a basic hydrological characteristic. Most prior studies have used remote sensing data to extract the river centerline from the open water region in a pure water pixel region. Extracting this type of river is relatively easy. However, extracting the centerline of a micro-river, which is mainly composed of mixed water pixels, is challenging. This paper presents a novel method, called the Multiple Direction Integration Algorithm (MDIA), to extract the river centerline using an image-enhancing method combined with river morphology. MDIA can be applied to regions mainly composed of pure water pixels, as well as to regions consisting of mixed water pixels in the index image. The method first calculates the normalized difference vegetation index (NDVI) and enhances the river linear structure using a Hessian matrix. Second, a small window is constructed as a circular structural element. In the window region, the local threshold is automatically obtained using water-oriented clustering segmentation and prior river knowledge to judge the pixel type. After completing the river centerline extraction in the current window, the next detecting window is generated to continue judgment. The structural element automatically executes river centerline judgment until the entire river centerline is extracted. The Landsat 8 images of six regions with different geomorphologies were chosen to analyze the method’s performance. The test sites include high mountain region, low mountain region, plains region with farmland and a residential region. The experimental results show that the optimal threshold of the processing results ranged from 0.2 to 0.3. In this range, the user’s accuracy is 0.813 to 0.997, and the producer’s accuracy is 0.981 to 1. The MDIA effectively and correctly extracts the river network in mixed-pixel regions. The presented method provides an effective algorithm for river centerline extraction that can be used to expand and update river datasets and provide reliable river centerline data for relevant hydrology studies

The role of rockfall intensity on its risk assessment

In many situations rock fall hazards cannot be eliminated because <span class="hit"><strong>the</strong></span> occurrence <span class="hit"><strong>of</strong></span> these hazards varies both spatially and temporally. Due to <span class="hit"><strong>the</strong></span> high mobility <span class="hit"><strong>of</strong></span> <span class="hit"><strong>rockfalls</strong></span>, their <span class="hit"><strong>intensity</strong></span> characteristics play important <span class="hit"><strong>role</strong></span> in <span class="hit"><strong>assessing</strong></span> their <span class="hit"><strong>risk</strong></span>. This paper discusses a <span class="hit"><strong>risk</strong></span> <span class="hit"><strong>assessment</strong></span> methodology by taking <span class="hit"><strong>the</strong></span> <span class="hit"><strong>intensity</strong></span> information <span class="hit"><strong>of</strong></span> <span class="hit"><strong>rockfalls</strong></span> into account. A <span class="hit"><strong>rockfall</strong></span> process modeling is performed to address such important <span class="hit"><strong>intensity</strong></span> information as frequency-magnitude relationship, runout distance, kinetic energy, and <span class="hit"><strong>the</strong></span> bouncing height <span class="hit"><strong>of</strong></span> rocks. A grid computing methodology is developed to combine important <span class="hit"><strong>intensity</strong></span> components <span class="hit"><strong>of</strong></span> <span class="hit"><strong>rockfalls</strong></span> for their <span class="hit"><strong>risk</strong></span> <span class="hit"><strong>assessment</strong></span>. A case study is conducted for <span class="hit"><strong>risk</strong></span> <span class="hit"><strong>assessment</strong></span> <span class="hit"><strong>of</strong></span> <span class="hit"><strong>rockfalls</strong></span> <span class="hit"><strong>of</strong></span> Du-Wen Highway. <span class="hit"><strong>The</strong></span> Due-Wen highway has been exposed to severe <span class="hit"><strong>rockfalls</strong></span> hazard induced by Wenchuan earthquake. <span class="hit"><strong>The</strong></span> <span class="hit"><strong>risk</strong></span> <span class="hit"><strong>assessment</strong></span> was performed <span class="hit"><strong>on</strong></span> a section <span class="hit"><strong>of</strong></span> Du-Wen Highway by combining <span class="hit"><strong>intensity</strong></span> characteristics <span class="hit"><strong>of</strong></span> <span class="hit"><strong>rockfalls</strong></span> hazard and <span class="hit"><strong>the</strong></span> vulnerability <span class="hit"><strong>of</strong></span> highway transportation. Different <span class="hit"><strong>rockfall</strong></span> scenarios have been taken into account involving combinations <span class="hit"><strong>of</strong></span> various <span class="hit"><strong>risks</strong></span> based <span class="hit"><strong>on</strong></span> different types <span class="hit"><strong>of</strong></span> consequences. Information <span class="hit"><strong>on</strong></span> historical records <span class="hit"><strong>of</strong></span> hazard events, frequency-magnitude and triggering mechanism provides additional insight to <span class="hit"><strong>the</strong></span> recognition <span class="hit"><strong>of</strong></span> <span class="hit"><strong>risk</strong></span> sites and <span class="hit"><strong>risk</strong></span> level. Further parameter calibration and expert judgment are required for practical <span class="hit"><strong>risk</strong></span> management. &copy; 2013 Taylor &amp; Francis Group, London

Seismic Response of Loess-Mudstone Slope with High Anti-Dip Angle Fault Zone

Earthquakes are one of the main factors inducing large-scale loess bedrock and especially loess-mudstone landslides in Western China, and these types of landslides are often closely related to fault zones. To study the influence of high anti-dip angle fault zones (HADAFZs) on loess-mudstone slopes (LMSs) during earthquakes, a scaled model with an HADAFZ of 80° using a shaking table test and numerical calculation, subjected to earthquake waves, was applied to reveal the rules of seismic response and failure characteristics. The acceleration dynamic response had a top surface amplification effect on the slope surface, an accelerated increase effect on the slope-surface hanging wall, an amplification effect away from the free slope face in the loess stratum, and a combination of elevation and lithology effects in the vertical section. At the loess–weathered mudstone (L–W) and weathered mudstone–mudstone (W–M) interfaces, the amplification response of a hanging wall was the largest, fault zone was the second, and foot wall was the smallest. Furthermore, the key value of input peak ground acceleration (PGA) for the dynamic response was a = 0.3 g. The hanging wall amplification effect became apparent while a > 0.3 g, and cracks appeared on the surface of the slope. The dynamic response of the soil pressure was influenced by the hanging wall amplification effect and had a positive correlation with the thickness of the overlying layers, both in the loess stratum and at the L–W interface. However, the dynamic soil pressure maximum variation (DSPMV) on both sides of the fault zone was larger than that in the fault zone. The development of an HADAFZ in the LMS hindered the integral connection of the potential sliding surface and restricted the overall sliding failure of the slope during the earthquakes