INSTRUMENTATION FOR FOUNDATION EGINEERING.

Introduction
Another broad category of construction services performed by geotechnical engineers is the installation of monitoring devices. There are many types of monitoring devices used by geotechnical engineers. The usual purpose of the installation of monitoring devices is to measure the performance of the structure as it is being built. Monitoring devices could also be installed to monitor existing adjacent structures, groundwater conditions, or slopes that may be impacted by the new construction.

Monitoring devices are especially important in urban areas where there are often adjacent structures that could be damaged by the construction activities. Damage to an adjacent structure can result in a lawsuit. Frequent causes of damage to an adjacent structure include the lowering of the groundwater table or lateral movement of temporary underground shoring systems. Monitoring devices are essential for adjacent historic structures, which tend to be brittle and easily damaged, and can be very expensive to repair. For example, Feld and Carper (1997) describe the construction of the John Hancock tower that damaged the adjacent historic Trinity Church, in Boston, Massachusetts. According to court records, the retaining walls (used for the construction of the John Hancock basement) moved 33 in. (84 cm) as the foundation was under construction in 1969. This movement of the retaining walls caused the adjacent street to sink 18 in. (46 cm) and caused the foundation of the adjacent Trinity Church to shift, which resulted in structural damage and 5 in. (13 cm) of tilting of the central tower. The result- ing lawsuit was settled in 1984 for about $12 million. An interesting feature of this lawsuit was that the Trinity Church was irreparably damaged, and the damage award was based on the cost of completely demolishing and reconstructing the historic masonry building (ASCE, 1987).

1 Commonly Used Monitoring Devices   Some of the more common monitoring devices are as follows: Inclinometers. The horizontal movement preceding or during the movement of slopes can be investigated by successive...

2 Development of an Instrumentation Program   Prior to the construction of the project, an instrumentation program may need to be developed. Figure 17.13 shows an example of an instrumentation program for a proposed 75 f...

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