Search results for: Latest H19-461_V1.0 Exam Questions Vce 🏯 H19-461_V1.0 Labs 🐒 H19-461_V1.0 New Study Plan 🙊 Search for ✔ H19-461_V1.0 ️✔️ on 「 www.pdfvce.com 」 immediately to obtain a free download 🧎H19-461_V1.0 Best Vce
-
Stabilisation of reactive subgrades by cementitious slurry injection – A review
Slurry Injection Stabilisation is a cost-effective method for the remediation of discrete sections of railtrack subgrade. It is generally applied to subgrade soils that experience fluctuations in strength and volume with varying seasonal moisture contents, thereby undermining the performance of the track. This technique involves the direct injection of cementitious slurry to the subgrade where it reacts with soil particles to enhance the strength and stiffness while decreasing permeability and plasticity.
The aim of the slurry injection operation is to expose as much volume of subgrade soil to chemically active slurry material as possible. The mechanics of slurry infiltration of the subgrade strata and the subsequent reaction of the cementitious additives within the soil mass are two distinct fields of study that influence the scale of subgrade improvement. These fields have been examined in order to develop a comprehensive account of the technical processes involved in the stabilisation technique. This should help the improvement of slurry design and injection procedures to suit site-specific subgrade conditions.
-
The role of micro-mechanics on the consolidation history of granular materials
A discrete element method (DEM) was used to investigate the undrained behaviour of granular materials under a critical state soil mechanics (CSSM) framework. The laboratory works within CSSM framework are mostly confined to an isotropic condition; therefore, the experimental data for the same granular material under different consolidated conditions was limited in the literatures. The research employs DEM to investigate the effect of different consolidation conditions, i.e. isotropic (the principal stress ratio, K=σ′3/σ′1=1), anisotropic (K=0.5) and K0- conditions, on the same granular material. It was found that the consolidation condition influenced the micro- and macro- mechanical properties and so their undrained behaviour during shearing. However, a unique critical state line (CSL) was achieved regardless of consolidation condition. The state of granular material is often defined in terms of initial state parameter (ψ0) using the CSL. The instability stress ratio (ηIS), which characterizes the triggering of instability or liquefaction, showed good relation with ψ0 and the relation is known as the instability curve. Multiple instability curves were found depending on the consolidation condition. The particle contact at the onset of instability in terms of coordination number (CN) was almost the same for the same ψ0 for all consolidation conditions, however the fabric anisotropy in terms of von Mises fabric (FvM) showed similar correlation with ηIS as found for instability curves. This suggests that the difference in instability curves for different consolidation conditions may be related to fabric anisotropy.
-
Real-time monitoring and wireless data transmission to predict rain-induced landslides in critical slopes
Real-time landslide monitoring is an effective technique to minimise landslide risks, especially in circumstances where the potential for structural countermeasures is limited. Rainfall infiltration is considered as one of the most significant factors triggering slope instability. Hence real-time monitoring of parameters: rainfall, volumetric water content and surface deformations/displacements in the soil, enable the early detection of landslides, thus reducing the adverse impacts of landslides. This study involves low cost and simple to install miniature ground inclinometers equipped with MEMS (Micro Electro Mechanical Systems) tilt sensors, volumetric water content sensors, temperature sensors, a rain gauge and a wireless data transmission unit (DTU) for the prior identification of possible slope failure. The DTU receives data from sensor units via radio signal transmission at a higher data acquisition frequency and automatically transmits them via the mobile network to an internet server, and updates in an online web interface for the determination of slope instability. The monitoring programme in operation for more than two years in the Lake Baroon Catchment, Maleny plateau, Australia, accurately captured both creep movement of the slope with wetting and drying cycles and mass movements triggered by rainfall. The current study analysed the surface deformation and rainfall data produced by the real-time monitoring system and validated results using published study outcomes. Herein, a combination of rainfall data, I-D threshold equations and ground tilting rate was identified as a more suitable measure to detect possible slope failure in advance. Further, the issue of a ‘precaution’ at a tilting rate 0.01˚/hr, and a ‘warning’ at 0.1˚/hr is recommended by this study along with the consideration of rainfall data.
-
Identification and treatment of areas susceptible to tunnel erosion
Tunnel erosion is a soil loss process that can lead to rapid and irreversible degradation of valuable land affecting both natural and man made landforms. Where natural landscapes are affected the value of grazing, farming and recreational land can be rapidly lost. In man-made landforms such as dam embankments or reclaimed land constructed as part of land restoration or urban development, the tunnels can be hazardous to the integrity of the landform, pose a risk of dam failure or cause a safety hazard to persons and vehicles.
This paper describes the characteristics of tunnel erosion as observed in a land development area in western Sydney and the measures used to identify and treat at-risk areas. The land affected is intended for residential development and had to be assessed in detail to determine whether remediation was required and, if so, then how this would be achieved. A Tunnel Erosion Identification Rating system and innovative test procedures were developed for the study that could have wider application other than just the affected landforms encountered in the study. Also, relationships were established that correlate chemical properties of the soil to the physical properties, thus reducing the need for expensive chemical testing of the soil.
-
Impacts of longwall mining and coal seam gas extraction on groundwater regimes in the Sydney Basin: Part 2 – Practical applications
Part 1 of this paper presented simple equations for transient and steady state downwards flow in saturate and unsaturated ground that are considered to be useful in understanding flow and pressure regimes above extensive areas of longwall mining and coal seam gas extraction. This Part 2 paper presents filed data from longwall mines in the Sydney basin and relates the data to findings from Part 1. This part also analyses how different views have been expressed in relation to impacts of longwall mining on groundwater regimes and proposes that these differences have largely arisen out of poor differentiation between seepage flows and pressures.
The field data presented in this part support a finding of Part 1, namely that the question that should be asked in respect to groundwater impacts from longwall mining, and CSG extraction, is not “if” impacts will occur, but “how long” will they take to occur.