Effect on Deformation due to Presence of Extra Bars in Column Heads

The purpose of the work is to investigate the effect of additional bars at column ends, when column is subjected to axial load. Due to this; reduction in the axial and lateral deformations of heads of the column are examined. The experimental study examined both ends' behaviour after providing extra bar at top head and bottom head of the column and experimental values indicate that presence of extra bars in column heads decreases axial and lateral deformation in the heads. The experimental values of axial and lateral deformations were validated with the help of ANSYS software. The variation in these values with respect to percentage of steel and grade of concrete is also studied.

Three-dimensional analysis of unanticipated behavior of a deep excavation

A three-dimensional (3D) effective stress finite element analysis, modified to account for hydrofracturing and gassy soil behavior, is used to examine the potential for the venting of water and gas from a bedrock aquifer and through 13–14 m of low permeability clayey silt between the base of the excavation and the bedrock following excavation to about 24 m in an approximately 40 m thick clayey silt deposit. The clayey deposit contained sand lenses with dissolved gas. The analysis predicts that the exsolution of this dissolved gas, caused by a reduction in total stress due to the excavation, results in liquefaction of the sand in the lenses and consequent lateral deformations of the side slopes. The analysis predicts hydrofracturing through the remaining clayey silt when the excavation reaches its final depth and this explains the venting of water and gas from the underlying aquifer that was observed above a local bedrock high. The presence of gassy sand lenses created weak zones within the clayey deposit that influenced the path of the hydrofracturing. However, the analyses suggest that, for the depth of excavation and bedrock elevation examined, hydrofracturing and subsequent venting would have occurred even if there had been no sand lenses.

Mechanical behaviour of rammed earth column: A comparison between unreinforced, steel and bamboo reinforced columns

This paper presents an experimental study on the behavior of cement stabilized rammed earth (CSRE) column reinforced with steel under axial loading and its comparison with unreinforced and bamboo reinforced columns. Effects of structural parameters such as tie / stirrup spacing on the failure pattern, lateral and axial deformation of columns are studied. Test results show that the load-capacity of columns increases with increase in lateral / tie reinforcement ratio. Maximum axial and lateral deformations occur in columns with least tie spacing. Behavior of CSRE columns reinforced with close tie spacing is characterized by gradual spalling of cover at the failure zone. Steel reinforced columns perform better than other column types in terms of load-capacity; hence it may be used as structural member adjacent to walls for low-rise rammed earth houses. Proposed reinforcement technique can be adopted in the field for enhancement of greater strength and performance of columns.

Numerical analysis of geogrid contribution to railway track reinforcement

In this work, influence of geogrids on overall stabilization of railway tracks is studied numerically. It is expected that by geogrids implementation significant reduction in the downward propagation of stresses will be obtained, which consequently should assure more resilient long-term performance. In this first approach, however, only added value to the confinement level of the ballast layer is analysed, by evaluation of lateral deformations. A case study is related to a part of the Portuguese railway network. The track and the passing vehicle are modelled in commercial explicit dynamics software LS-DYNA. Firstly, the model is validated by comparison with experimental data. Then a fictitious scenario of the same track with a deteriorated region which is further rehabilitated by the geogrid placement is analysed. Different situations are compared in terms of lateral and vertical displacements at several levels, but for simplicity only rail deflections are shown here.

Estimating Actual 2D Ground Deformations Induced by Underground Activities with Cross-Heading InSAR Measurements

InSAR can only monitor relative ground deformations with respect to a reference area. In order to obtain actual deformations, GCPs or stable area is required in the study area, which, however, may be unavailable in the investigating of geohazards associated with underground activities (i.e., groundwater pumping, underground mining, and oil/gas exploitation). We propose a novel approach to estimate actual 2D deformations based on the InSAR relative LOS measurements acquired from cross-heading datasets. The errors induced by the arbitrary selection of reference areas can thus be avoided. The performance of the proposed approach is validated by a series of simulations. By providing the ascending and descending measurements with errors of 2 and 1.5 mm/year STDs, respectively, the RMSEs are 2.1 and 2.6 mm/year for the estimated vertical and east deformations, respectively. A case study is carried out in Cangzhou, China, for estimating the actual 2D ground deformations associated with groundwater pumping. By integrating ALOS ascending and ENVISAT descending datasets acquired between 2007 and 2010, we found that the Cangzhou area experienced ground subsidence of up to 23.4 mm/year in the suburbs but ground uplift of up to 20.9 mm/year in the urban area, both of which are accompanied by considerable lateral deformations.