Sloping excavations

Figure 6. Slope excavation and protection, 1-cut slope 2-backfill surface 3-bolting 4-drainage 5-flexible protection 6-monitoring system...

Recently, many studies have focused on this topic, however, information on slope excavation... 

Based on field observations and analysis of an open-pit mine, the kinematic behaviors of fault reactivations induced by slope excavation were identified and studied in this paper. The results will be helpful to the stability assessment, disaster prevention, and trend forecast of excavated slopes. 

TYPICAL FAULT REACTIVATIONS AND MECHANISMS CAUSED BY SLOPE EXCAVATION... 

Figure 6. Checkerboard-patterned fault reactivation caused by slope excavation. 

This topic is of course very important in engineering practice. Many geotechnical professionals are uncertain how to interpret readings from piezometers in non-hydrostatic conditions. This becomes very important when interpreting conditions in an unstable slope or comparing assumed or predicted conditions in finite element analyses (e.g. using Plaxis) with the field conditions they are supposed to represent. Misconceptions about the water regime often contribute to major failures in slopes, excavations and tunnels. 

All simple slope excavations 20 feet or less in depth shall have a maximum allowable slope of 1 V2 1 ... 

All other sloped excavations shall be in accordance with the other options permitted in 1926.652(b). 

After initial mine development work, a phase of slope excavation and preparation is undertaken to prepare the orebody for full extraction. Tbe sequence of operations that follows involves breaking up the ore material (by drilling and blasting), removal of the ore and its transportation to a concentrator (haulage). Haulage includes hoisting operations and conveyor, rail or truck transportation. 

A smooth coal pile surface, coupled with the gradual slope, minimi2es the differential wind pressures and consequent oxygen penetration. A 4-6 X 10 t lignite stockpile from the excavation for the Garrison Dam in North Dakota has been stable for many years as a result of this storage method. 

The top layer of the detonation ground was excavated to a depth of 0.5m. The exeavated soil was temporarily stored on the site. A Bentonit seal was installed and a protective and a drainage layer were built over the seal. The excavated soil was incorporated into the slopes of the reconstructed ground (Figure 6). The new top layer of the detonation ground was made Irom... 

The banks around evaporation ponds can be built from the existing soil and excavated earth. It is suggested that a layer the topsoil be removed from the pond area, and the subsoil underneath be used to form the inside of the bank. The outer slope of the bank can be covered in the removed topsoil, as this promotes the regrowth of vegetation (Singh and Christen 2000). An example of this is shown in Fig. 7.4. 

Contour mining is used in hilly areas, where the slope of the surface will permit only a narrow bench cut around the side of a hill the excavation is backfilled immediately after the removal of coal. It is the only method that can be used on slopes of 15 degrees or higher. 

With the exception of these small amounts of meteoritic matter, the lunar soil is derived from igneous rocks disrupted by impacts and gradually reduced to fine-grained dust. On all landing sites, the soil is much more abundant than rocks or breccias. Except on steep slopes, the whole Moon is covered with a layer dust of at least 5 m thick. The rock samples brought back are separate fragments embedded in the soil once part of the underlying bedrock, they were excavated by the impact of meteorites. 

K roly Hoffmann discovered in 1874 clefts filled with red clay in a quarry on the northern slope of M szkohegy (Templomhegy), the most easternly peak of the Villdny mountains ( the quarry opposite to the railway station ). Later, Loczy, Jr. collected from the large quarry on the ridge of the hill (then called the quarry of Prince Frederick ). Kormos had worked for 30 years on the material of various clefts and finally Kretzoi (1953-1955) and myself (from 1975) have carried out excavations. Of the 11 Villany localities listed by Kretzoi (1956), nos. 3, 5 and 11 will be discussed here because of their relevant age. 

I describe here in detail the nominate fauna of the Istallosko cave. The locality is a cave formed in Triassic limestone on the southwestern slope of Istdlldskd in the Biikk Mountains, at an altitude of 535 m a.s.l. The hollow itself is about 45 m long and 8-10 m wide. Hillebrand was the first to excavate in the cave (in 1912), then Kadic, Mottl, Saad, Hillebrand, Vertes and myself made collections on thirteen occasions. 

A combination method is called the progressive slope or ramp method, where the depositing, covering, and compacting are performed on a slope. The covering soil is excavated in front of the daily cell. Where there is no cover material at the site, it is then brought in from outside sources. 

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. 

Nailing is done to protect slopes as excavation proceeds—that is, it is a process that works from the top down. In contrast, when fill is placed to raise an area, the slope is created from the bottom up. For high fills, it may be necessary to reinforce the soil in order to prevent a slope failure. This may be done with geotextile sheets, which are placed horizontally to cover the entire fill surface at vertical intervals of several feet. The geotextile sheets add shear resistance to possible slip or failure planes. In order to be effective, the sheets must extend a significant distance beyond the failure planes for unreinforced soil. Rigorous design procedures are not yet available, and the parameters for field use are selected on the basis of past field experience. 

Soil nails are similar to ground anchors, but on a much smaller scale, and they are not pretensioned. Nails are installed on a grid from the top down, as a slope results from excavation. Reinforced fill is a method of supporting a slope as it is being constructed, from the bottom up. Geotextile sheets are applied over the entire fill on layers several feet apart. Like nails, the sheets add shear resistance to the soil mass. 

The requirement of water shut-off and strength increase may be interrelated. The stability of an excavation face or a slope in fine-grained granular material is lowered by the flow of water through the face. Thus water shut-off must be accomplished in order to increase strength. Grout selection for such cases is also based on penetrability. 

Barricading or isolating the work site, to prevent close approach by unauthorized persons. Placement locations for earth or other materials that are removed from the excavation. Protection provided against cave-in or collapse of trench or excavation walls, using shoring and/or sloping. 

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