Trenches excavations

Hematite in the soil is concentrated in spherules and their fragments, which are abundant on nearly all soil surfaces. Several trenches excavated using the rover wheels showed that the subsurface is dominated by basaltic sand, with a much lower abundance of spherules than at the surface. Olivine-bearing basaltic soil is present throughout the region. At several locations along the rover s traverse, sulfate-rich bedrock outcrops are covered by no more than a meter or so of soil. 

Slurry Transportation Piping, 19 480 Slurry trench excavation... 

Site facilities such as underground piping preclude practical trench excavation. 

Well construction minimizes the generation of significant quantities of potentially hazardous soils in contrast to significant volumes potentially generated by trench excavation. 

Samples were collected from a 2-m deep trench excavated prior to mining from the Bounty Gold Deposit in Western Australia. Bulk soil samples were analysed by ICP-... 

Trenches excavated across the veins are typically flooded by surface water however, three partially flooded trenches have exposed bedrock. From small (< 5m ) outcrops exposed in three of the trenches, it is apparent that the average grain size of the clastic sedimentary rocks and the abundance of coarse-grained detritus, increases from NE to SW away from the buried Caradocian shale, with arkosic sandstone most abundant in the SW near the Christopher vein. An extensive array of 98 drill holes provides excellent downhole, 3-D control on our understanding of the geology. 

Chemically resistant masonry joints in clay pipe are rigid. Ground movement, such as settlement, can therefore break the pipe. For this reason it is important that all industrial waste lines be laid with continuous support. No matter what opinion others may have of the stability of the soil in the area where the pipe is to be laid, this writer has never seen any trench excavation, no matter how well prepared, that did not require adjustment to attain the suitable smooth surface and slope after the trenching operation had been completed. These adjustments require fill in some spots and further surface removal in others. In addition bell excavations are required to provide working room to make the joints. After the line is in service, heavy rains, flooding and even percolation of groundwater can cause soil movement above and around the pipe, and eventually, without uniform support, movement will take place that breaks the pipe. 

Ward, W.H. The Use of Simple Relief Wells in Reducing Water Pressure A Trench Excavation. Proceedings of the Institution of Civil Engineers Geotechnical Engineering 119, pp 231-236, October 1996. 

The location site of the mosque is within the Kenny Hill Formation (quartzite and phyllite) of Kuala Lumpur, Malaysia. Inspection trenches excavated for examining the existing foundation and deep soil investigation boreholes revealed that the top 5 m was loose silty sand underlain by 3 m of medium dense sand. Below this were residual soils followed by weathered quartzite and phyllite of the Kenny Hill Formation. 

However, if you work in trenches/excavations you should know much of the same information your competent person does. Why A sudden change could mean disaster for you and fellow workers. 

To remove employees from the trench/excavation if any of the above hazards exist. 

Explain the requirements for means of egress from the trench. A stairway, ladder, ramp or other safe means of egress must be located in trench excavations that are 4 feet or more deep. The means of egress must close enough so as to require no more than 25 feet of travel for employees. 

Point out safety devices on an actual vehicle. Demonstrate spotter signals. Ask trainees to talk about any incident or near-miss backup incident. Have trainees pretend to be the site engineer for a site with a trench, excavator, storage area, fueling area, office trailer, and two dump trucks and one pickup going in and out of the site. Have them take 10 minutes to decide where vehicles are going to work, travel, and park and where employees on foot will be, all with the intent to reduce the risk of backup incidents. 

Information on the clearances that must be maintained between vehicles, and hazards, such as unstable surfaces, trenches, excavations, and overhead utility lines and... 

Figure 30.4 Trench excavation using steel trench sheets as runners. (BS 6031 1981f. Note Stages 1 and 2 are shown in the British Standard...

Position spoil heap at a distance not less than half depth from the edge of excavation. Tip if possible on blind side of excavator to ensure operator has visibility when swinging back to trench excavation. Provide personal protective equipment. 

Trench (Trench excavation) means a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width, but the width of a trench (measured at the bottom) is not greater than 15 feet (4.6 m). If forms or other structures are installed or constructed in an excavation so as to reduce the dimension measured from the forms or structure to the side of the excavation to 15 feet (4.6 m) or less (measured at the bottom of the excavation), the excavation is also considered to be a trench. 

Additional requirements for support systems for trench excavations, (i) Excavation of material to a level no greater than 2 feet (.61 m) below the bottom of the members of a support system shall be permitted, but only if the system is designed to resist the forces calculated for the full depth of the trench, and there are no indications while the trench is open of a possible loss of soil from behind or below the bottom of the support system. 

This is the traditional method of trench excavation and relies on the strength of the soil to support the trench walls. There is no safe depth for this technique since all soils vary in cohesiveness and many soils consist of a mixture of sand, gravel and clay. For many soils, the angle of repose of the sides (measured from the horizontal plane) is approximately 30°. This means that such excavation covers a considerable area. It is generally recommended that this type of excavation should not exceed 1.2 m in depth. 

If the bund has to be constructed on soft subsoil, stability considerations may require a staged construction with a limited height for each lift and a gentle overall slope. Alternatively, it may be possible to construct the bund on top of a trench excavated into the soft soils see Figure 6.5. Another solution is to increase the shear strength of the subsoil prior to or during construction of the bund by soil improvement techniques as discussed in Chapter 7. 

Hazard communication Fire extinguisher Confined space Trenching/Excavation Supervisor training HAZWOPER initial training HAZWOPER refresher training HAZWOPER 3-day OJT HAZWOPER supervisor Safe driver training Asbestos (ACM) PM ACM Supervisor ACM Project Designer ACM Worker... 

On cultivated lands, firstly, it is important to get the permission of the landowner but the local authorities must also be informed. The contact also provides logistic information for researchers about the existence of any possible human-made structures, such as waterworks, electricity cables, and oil/gas pipelines, which can easily be destroyed during a trench excavation. Moreover, these authorities, like local municipalities, may help in finding the work machines, which are used in trenching. 

The choices for trench excavation depend on several factors such as the kind of material being trenched, the width of the deformation zone, the fault type, the relief of the site, the target depth, the stability of the trench walls, and the style of working. 

Table 1. Stability of vertical sides of a trench excavation in soil with crust 1 -5-2 m thick...

Fig. 1. Trench excavation in conjunction with support by poling boards and walings...

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