(c) The pipes should be located such that gas rising vertically to
the underside of the floor slab does not have to travel more than 25 feet
laterally through the stone to reach a pipe.
(d) The pipes can be connected to a single, non-perforated pipe of
6-inch diameter, and vented to the atmosphere at roof level.
Further details on gas detection and venting can be found in
References 21, Sanitary Landfill Design Handbook, by Noble, and 22, Process
Design Manual, Municipal Sludge Landfills, by the EPA.
Section 10.
FIELD INSTRUMENTATION
1. UTILIZATION. Field instrumentation is used to measure load and
displacement and to monitor changes during and after construction. This
allows verification of design assumptions and performance monitoring, which
could indicate the need for implementation of contingency plans or design
changes. For additional guidance on planning and performing geotechnical
monitoring see Reference 23, Geotechnical Instrumentation for Monitoring
Field Performance, by Dunnicliff. See Reference 24, Equipment for Field
Deformation Measurements, by Dunnicliff, for instrumentation devices in
current use. See Figure 15 for an example of instrumentation adjacent to a
building and diaphragm wall.
a. Survey Technique. The most common uses of optical survey techniques
are for the determination of changes in elevation, or lateral displacement.
The laser geodimeter provides a significant reduction in time as well as
increased accuracy in monitoring of slopes. Survey techniques can be used
effectively to monitor surface movement of building and adjacent ground
movement of slopes and excavation walls. Figure 15 shows an application of
optical surveys.
b. Monitoring of Settlement and Heave. Many devices are available for
monitoring settlement and heave, including a number which will permit
measurement of the compression of the separate soil layers. Vertical
movement can also be measured by remote settlement gages utilizing closed
fluid systems, and by extensometers embedded beneath foundations in an
incompressible layer. These devices are also well suited to measuring
heave. For a more detailed description of field instrumentation equipment
see Reference 22, and the latest brochures of geotechnical instrumentation
companies.
c. Horizontal and Slope Movements. In addition to conventional
surveying techniques, horizontal movement can be measured by horizontal
movement gauges, inclinometers, and extensometers. Inclinometers are
especially useful for monitoring horizontal soil displacement along the
vertical face of a cofferdam or bulkhead, or as in Figure 15, adjacent to an
excavation. Tiltmeters can provide very precise measurements of slope
changes in soil and rock formations or in structures.
7.1-110
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