Load Transfer In Soil Anchors – Finite Element Analysis Of Pull-Out Tests

Soil anchors are widely used to stabilise soils and provide additional support to earth retaining structures. They are found in critical civil infrastructure such as transportation networks like highways and railways. Understanding their behaviour is important for the safety of these structures and the public. Therefore, careful design with appropriate soil parameters is required to ensure their efficiency.Finite element (FE) analysis is a powerful engineering tool that is able to predict the response of soil anchors. Various types of FE models are used, such as 2D axisymmetric or full 3D solid continuum and the more practical load-transfer FE analysis. Usually relevant field or laboratory tests are required in order to define the model parameters. Field pull-out tests are one of the most common and reliable type of such tests.This study presents field data from such field tests that were carried out on in-situ ground anchor systems, using strain gauges to evaluate the changes in the variations of axial load and skin friction along the nail during the tests. The results of these field tests provide details about the development of skin friction with induced displacements, thus offering the opportunity to perform load-transfer finite element analyses of the soil anchor.A FE model based on the load-transfer approach is developed to analyse this soil-structure interaction problem. A number of FE analyses using parameters derived from the field tests are run to validate the finite element load-transfer models which are compared with the field test results and exhibit an excellent agreement

Displacement mapping of point clouds: application of retaining structures composed of sheet piles

AbstractThe measurement of displacement is an important factor to evaluate the stability of a retaining structure. In this paper, a large-scale retaining structure with a width of 70 m and a height of 6 m was monitored using 3-D laser scanning. Displacement mapping was proposed to globally monitor the entire retaining structure. The point cloud obtained immediately after the excavation was converted into the mesh, and the point clouds obtained on the second and seventh days after excavation were compared to the mesh using the Cloud to Mesh (C2M) comparison method. Since the C2M displacement can be underestimated in the inclined section of the sheet pile, after filtering using the azimuth and element angles automatically, only the flat sections of the sheet pile can be segmented from original point clouds collectively and consistently. The displacement mapping results identify not only the local behavior of the sheet pile, such as the bending point and the maximum displacement position, but also the global behavior, such as the expansion of the maximum displacement in the retaining structure. The results of the displacement mapping were confirmed through site investigation as well. In the displacement mapping result, the maximum displacement was found around rows 2 and 3 of the 37th sheet pile, and the analyzed result of the load cell installed on the anchor indicated that the anchor constructed in the 37th sheet pile shows the plastic behavior. It was established that other sheet piles are affected by the damage to the local anchor through the H-beam and the maximum displacement in the displacement mapping is expanded horizontally in a positive parabola shape. Therefore, it was confirmed that displacement mapping using laser scanning can complement existing monitoring techniques and can contribute to evaluating the behavior of a large-scale retaining structure during excavation.</jats:p

Observation of trapped-modes excited in double-layered symmetric electric ring resonators

We report on experimental observations of trapped-mode resonances in double-layered symmetric electric ring resonators separated by dielectric inserts. The resulting metamaterial introduces trapped-mode resonances that were thought to be produced only by asymmetric metamaterial unit cells. Experimental verification of the newly observed trapped modes, along with the analysis of the stacked metamaterial geometry reported in this paper, opens an alternative way of forming sharp resonances in a symmetric metamaterial structure extended in all three dimensions.open9

Net load‐displacement estimation in soil‐nailing pullout tests

Soil-nails are used to stabilise a soil mass by exploiting the resistance generated by the skin friction between the ground and grout and the tensile stiffness of the reinforcing material. A load–displacement curve is obtained from in situ pullout load tests performed by considering the elastic shear modulus and ultimate skin friction capacity between the soil and grout. This study determines the shear behaviour between the soils and grout analytically, especially the soil-dilation effect during shearing that is one of the main factors affecting the ultimate skin friction, even though this estimation is rather cumbersome. Many studies assume a full bond between the grout and the steel reinforcing bar, thus neglecting their relative displacement. In this study, the net load–displacement between the ground and grout is obtained by subtracting the nail elongation from the load–displacement of the pullout tests when estimating the shear displacement. Numerous field pullout tests are performed in this study under various ground conditions and through various construction methods. The dilatancy angles are estimated dependent on the soil type by comparing the net load–displacement curve obtained in the field with that obtained theoretically. </jats:p

WaterScenes: A Multi-Task 4D Radar-Camera Fusion Dataset and Benchmark for Autonomous Driving on Water Surfaces

Autonomous driving on water surfaces plays an essential role in executing hazardous and time-consuming missions, such as maritime surveillance, survivors rescue, environmental monitoring, hydrography mapping and waste cleaning. This work presents WaterScenes, the first multi-task 4D radar-camera fusion dataset for autonomous driving on water surfaces. Equipped with a 4D radar and a monocular camera, our Unmanned Surface Vehicle (USV) proffers all-weather solutions for discerning object-related information, including color, shape, texture, range, velocity, azimuth, and elevation. Focusing on typical static and dynamic objects on water surfaces, we label the camera images and radar point clouds at pixel-level and point-level, respectively. In addition to basic perception tasks, such as object detection, instance segmentation and semantic segmentation, we also provide annotations for free-space segmentation and waterline segmentation. Leveraging the multi-task and multi-modal data, we conduct numerous experiments on the single modality of radar and camera, as well as the fused modalities. Results demonstrate that 4D radar-camera fusion can considerably enhance the robustness of perception on water surfaces, especially in adverse lighting and weather conditions. WaterScenes dataset is public on https://waterscenes.github.io

Tilt mapping for zigzag-shaped concrete panel in retaining structure using terrestrial laser scanning

AbstractTraditional monitoring systems are not able to monitor the global behavior of large retaining structures, and terrestrial laser scanning was performed for monitoring a retaining structure for this paper. The three-dimensional point cloud was obtained by scanning at seven locations with seven reference targets to cover the retaining structure having 180 m length and 25 m high. To evaluate the long-term behavior of the retaining structure, point clouds obtained by performing eight laser scanning at the same locations over 4 years were compared with each other. In this paper, the tilt mapping method was applied to define the global behavior of the entire retaining structure. The P2P-TA (Plane-to-Plane-Tilt Angle) comparison method was used to calculate the tilt angle by comparing the normal vectors of the planes created by the point clouds, because simple comparison methods are not able to be applied to compare points clouds of zigzag-shaped concrete panels. A laboratory test was conducted to determine the applicability of laser scanning and P2P-TA analysis, and the error range was conservatively set to 0.15°. The results of laser scanning and P2P-TA analysis applied to 231 concrete panels are shown in the tilt mapping of the retaining structure. The differential tilt angle was significantly increased every year at the bottom of the concrete panel adjacent to the tunnel. It can be seen that the concrete panel having a large differential tilt angle affects the differential tilt angles of others, because it is linked to other concrete panels.</jats:p