Tunnel entrance crossing spoil heap deformations control by micropile combine with coupling beams

Aiming at the deformation control problem of the tunnel entrance crossing the spoil heap at the Xialao junction,this paper adopts the micropile combined with the coupling beams method to treat the spoiled layers.The results show that the excavation of the tunnel after the construction of the micropile and coupling beam will cause vertical deformation of the tunnel and the slope surface.The main reason is that the soil layer structure is loose,and the tunnel excavation causes the whole displacement of the loose body.In addition,the buried depth of the tunnel is shallow,so it cannot form an effective soil arch.The stability process after the construction of the micropile method is the process of stress redistribution,and the rock and soil are gradually compressed and compacted.That is,the construction by the micropile method changes the surrounding rock level of the tunnel and reduces the height of the soil arch.Therefore,it is suggested that the tunnel excavation should be carried out when the micropile is constructed after the soil layers are consolidated completely.The micropile method treats the loose spoiled soil at the tunnel entrance,which saves 73%of the total cost compared with the scheme of directly digging out the accumulation,and the economic benefit is very obvious.

Sensitivity analysis of parameters and contrasting performance of ground filtering algorithms with UAV photogrammetry-based and LiDAR point clouds

Most ground filtering algorithms are primarily designed for airborne LiDAR point cloud processing and their successful use in identifying ground points from photogrammetric point clouds remains questionable.We compared six ground filtering algorithms implemented in Metashape,ArcGIS,CloudCompare,LAStools,and PDAL.We used UAV photogrammetry-based(acquired under leaf-off conditions)and airborne LiDAR(leaf-on)point clouds of the same area to:(i)compare accuracy of generated DTMs;(ii)evaluate the effect of vegetation density and terrain slope on filtering accuracy;and(iii)assess which algorithm parameters have the greatest effect on the filtering accuracy.Our results show that the performance of filtering algorithms was affected by the point cloud type,terrain slope and vegetation cover.The results were generally better for LiDAR(RMSE 0.13–0.19 m)than for photogrammetric(RMSE 0.19–0.23 m)point clouds.The behavior in varying vegetation and terrain conditions was consistent for LiDAR point clouds.However,when applied on photogrammetric point clouds,the algorithms’behavior was inconsistent,especially in areas of steep slope(except for the Progressive Triangulated Irregular Network in LAStools).Parameters related to the selection of the initial minimum elevation ground points were the most influential in all algorithms and point clouds.