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Deep soil mixing tour
Tamar Estuary River Health Action Plan (TERHAP) project
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Rock-falls into water and potential wave damage
This paper presents the findings of experimental work undertaken to investigate the potential wave damage caused by rock-falls into partially water-filled open pit mines. A particular mine geometry has been used to model the situation in a wave flume, with a modelled rock-fall of 10,000 tonnes. The main findings of interest to the mining industry are: a) transfer of energy efficiency from a rock-fall to the water ranges between 5% and 80% depending on slide impact velocity; b) maximum wave run-up distance up slope is about 40 metres; c) available evacuation times for personnel located at a pumping station within the maximum wave run-up distance is about 37 seconds, which is insufficient.
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Pile settlement zones above and around tunnelling operations
This paper describes briefly the method of analysis of the response of a pile to tunnelling-induced movements, including estimation of the loss of axial capacity. The various pile settlement “zones” computed from this analysis are compared with those measured experimentally for tunnels in sand by Jacobsz et al. (2001). Some theoretical differences are identified between the cases of tunnels in sand and in clay. Finally, for an example case of a structure over a tunnel, a comparison is made between the performance of three alternative foundation types, a piled foundation, a piled raft foundation and a raft foundation without piles. It is shown that the tunnelling induced movements have less influence on the latter two foundation types than on the fully piled foundation.
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Cyclic Response of Railway Subgrade Prone to Mud Pumping
Given the fast pace of growth in today’s world, the need for a cost-effective and sustainable mode of transportation is indispensable. Railways provide a mode of mass transportation which facilitates travel between two places. Rails are often laid on subgrade soils with difficult conditions such as low bearing capacity, and high groundwater tables, etc., so when trains pass over these challenging ground conditions, the subgrade softens into a slurry and starts pumping the fines into the upper ballast layers. In Australia, this phenomenon is commonly known as mud pumping or mud holes. This paper investigates the cyclic response of subgrade prone to mud pumping. It is observed that the cyclic stress ratio (CSR) has a threshold value beyond which the cyclic axial strains and mean excess pore pressures rapidly accumulate. An empirical model is proposed to capture the generation of mean excess pore pressure in relation to the applied CSR. Further, numerical simulations have been carried out using PLAXIS2D to model vertical drain inclusions in the railway subsoil. The results indicate that vertical drains not only reduce the accumulation of excess pore pressure but also assist in their dissipation under cyclic loading, thereby providing a viable alternative to mitigate the effects of mud pumping.
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The Application Of Permanent Shotcrete And Sprayed Membrane In Soft Ground Tunnels
Short and variable profile tunnels such as cross passages and Y-junction caverns in soft ground require an open faced
‘mined’ tunnelling approach. Traditionally these mined tunnel approaches relied on forward support and temporary
shotcrete with a second pass permanent concrete lining. Advances in forward support, shotcrete and membrane technology has enabled contractors to utilise shotcrete as a permanent lining element in soft ground and low cover environments that have greatly reduced overall construction duration and surface impacts. A number of smaller tunnel projects have recently been built in Australia utilising shotcrete as the permanent lining with extremely shallow cover.The paper focuses on the innovations and experiences gained in adopting this type of approach from the perspective of the tunnelling contractor.