Subsurface pitting

S-28 Br- 200 1500 15.000 30.000 Severe subsurface pitting Severe subsurface pitting... 

Burn Pit. This pit is at the end of the blooey line and provides a location for the cutting returns, foam and for natural gas or oil products from the subsurface to be ignited by the pilot light and burned off. The burn pit should be located away from the standard mud drilling reserve pit. 

FIGURE 22.1 Aspects of metallic corrosion (a) uniform general (b) nonuniform general (c) localized (spots) (d) large pits (e) small pits (/) intercrystalline (g) subsurface. 

We use sampling grids mainly for surface soil sampling, however, it is not unusual to place soil borings and collect subsurface samples on a grid pattern. Grids are also used for soil sampling from the bottom and sidewalls of excavation pits and trenches. 

In the course of remediation projects we often need to sample from the bottom and sidewalls of excavation pits. A variation of excavation pit sampling is sampling from test pits and trenches. Test pits are small excavations usually made with a backhoe for a purpose of collecting a subsurface soil sample. A trench is a long and narrow excavation originating from a pipeline removal or placed with earth moving equipment for exploratory purposes. 

Another, easily detected, example of structural changes in fruit tissue is that of bitter pit, which causes necrosis of the subsurface tissues in apples this in turn creates a localized dehydration such that the bitter pit spot appears white when using a very simple, one-band (1200nm) setting (Figure 8.7). 

Another defect, which is more difficult to detect than bruises, is bitter pit this appears as a subsurface necrosis of apple tissues, as spots of 2-5 mm diameter. Bitter pit appears as white spots in NIR images, as do old bruises showing dehydration (see Figure 8.7). 

The utility of explosives lay in the strongly energetic and exothermic reaction initiated upon detonation or ignition. Most modem explosives are reasonably stable and require percussive shock or other triggering devices for detonation. Fortunately, subsurface Explosives-Associated Compounds (XAC) contamination usually occurs as dilute, aqueous solutions and thus presents no explosion hazard. However, masses of pure crystalline explosive material have been encountered in soils associated with wastewater lagoons, leach pits, bum pits, and perhaps firing ranges. 

CF cracks are always initiated at the surface, unless there are near-surface defects that act as stress concentration sites and facilitate subsurface crack initiation. Crack initiation takes place independently of fatigue limit in air as it can be decreased or eliminated through the increase of dissolution rates at anodic sites. Localized corrosion such as pitting favors fatigue crack initiation through stress concentration and a local acidic environment. The two main mechanisms of CF are anodic slip dissolution and HE (80). 

Subsurface investigations and sampling-. The objective is to determine the groimd conditions for geotechnical design, performance and detect potential difficulties and problems. There are various methods to obtain samples that include the digging of test pits, trenches and boreholes. 

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