Application of Laser Scanning to Assess the Roughness of the Diaphragm Wall for the Estimation of Earth Pressure

Abstract

The correct estimation of earth pressure is important for the design of earth retaining structures and depends, among others, on the surface morphology of retaining structures. The diaphragm wall created as a protection of a deep excavation located in an urbanized area was selected as a research object. Terrestrial Laser Scanning (TLS) was used for the investigation of the unique surface (in real-world dimension) obtained by tremieying the concrete in different soil layers. An original and innovative procedure for concrete surface description was developed, which includes steps from the TLS measurement to the determination of the roughness parameters. The tested samples from anthropogenic soil, medium sand, and sandy gravel, map the real diaphragm wall surface. The surface roughness parameters in different soil layers were compared with the reference surface obtained by cast against steel formwork. The following parameters: Sa, Sdr, and Vmc are indicated as being the most useful in numerical description of the concrete surface type and in allowing the determination of the soil surface friction. The novelty of this study is the estimation of the parameter δ (friction angle between the retaining wall surface and the soil), which is, among others, a function of the wall surface roughness. The influence of the type of surface on earth pressure are generally recognized in laboratory tests. Based on the estimated in situ values of δ, the more reliable active and passive pressure coefficients Ka, Kp were calculated for the tested soil layers. The conducted study has a practical significance for designing of retaining construction and makes progress in determination of surface roughness required in Eurocode 7.

Error Analysis of Stonex X300 Laser Scanner Close-range Measurements

“…However, the reduction in the mean error was gradually decreased as the range increased to 30 m. The results proved the validity when the data was correctly analyzed and the error uncertainty was manipulated correctly to reduce the noise level. This was based on the careful selection of the kernel parameter that was used in the roughness tool and the roughness-assumption algorithm [35]. It is worth mentioning that the level of noise in the Stonex X300's range measurements increased as the range decreased and approached the minimum range of the range-finder component (see [23] for further details).…”

Hazard Reduction in Deep Excavations Execution

“…The type of sensors and their arrangement scheme depends on the type of housing. The lining considered by the authors-a diaphragm wall-is an example of a reinforced concrete lining, which allows for the execution of a deep excavation suitable even for several underground floors [26]. It is particularly important to monitor this type of support because it is a complex system, which is subject to many different loads that change in time, such as loads caused by construction equipment at the ground level, operational load inside the trench, soil pressure, thermal loads, and groundwater pressure.…”

Comparison of TLS and SLAM technologies for 3D reconstruction of objects with different geometries

“…Laser scanning can be applied in various fields, such as geodesy, civil engineering, urban planning, architecture, or mining. 3D data can be used, e.g., for monitoring the geometry of engineering structures or infrastructure [3,4,5], surface roughness assessment [6], 3D city modeling [7], BIM [8], architectural conservation [9]. In the mining sector LiDAR technology is often used to map underground tunnels and evaluate IOP Publishing doi:10.1088/1755-1315/1295/1/012012 2 their geometry [10,11], utilize 3D models of tunnels to analyze airflow [12] or to monitor the condition of mining infrastructure [13].…”