Instrumentation & Monitoring

Building Settlement Marker

The purpose of this test is to determine the vertical displacement of existing building infrastructure due to ground excavation and construction activities.

The building settlement marker consists of 16mm diameter steel female socket and stainless steel male threaded plug to fit into female socket.

A precision leveling equipment is used for the monitoring of the Building Settlement Marker.

  
Crack Monitoring Using Demec Gauge

The method described here covers the use of DEMEC gauge to monitor the widening or closing of cracks on exposed concrete surfaces.

The DEMEC gauge consists of an Invar bar to which is attached the body of a dial gauge. A fixed point is provided at one end of the Invar bar, and a movable point is pivoted at opposite end. The movement of this point is measured by the dial gauge. The points are used to sit on DEMEC stainless steel studs attached to the concrete surface across the width of a crack. The widening or closing of the crack width will cause the distance between the studs to lengthen or shorten respectively, and this can be measured by the dial gauge of the DEMEC gauge.

Inclinometer

In soft ground situation, these instruments are installed to monitor the large lateral displacement that are just below a desicated crust.

An inclinometer consists of a tiltsensor torpedo usually fitted with sprung wheel and containing a gravity operated tilt sensor which generate a signal to a readout unit which is connected to a power source. The signals are captured to enable the determination of the angle between the torpedo axis from the vertical.

Measurement of tilt and probe depth are used to compute the horizontal deviation of the guide tube from the vertical.

The instruments measure ground movement only in the direction perpendicular to the borehole axis.





Open Standpipe

This test is commonly employed for the purpose of monitoring the ground water levels.

Borehole drilled during the course of site investigations can be left open or cased if necessary to provide an observation point.

The open standpipe generally consists of a 25mm or 50mm diameter PVC pipe with perforations or slots over its lower end and installed in the completed borehole. A dipmeter is used to measure the levels of water from ground surface in the open standpipe.



In-Situ Pressurremeter Test

The purpose of performing the borehole pressuremeter test is to measure the strengths and the deformation of soil or rock.

The apparatus consist of radially expendable cylinder probe (Pressuremeter probe) a pressure measuring unit (pressure gauge), a volume measuring unit (Volumeter) and back pressure annular plastic tube (double tubing). The pressuremeter probe is BX 58mm diameter with three independent cells, namely, two guards cell at both ends and a measuring cell at the centre. One commonly used instruments is Menard Pressuremeter.

The pressuremeter test is carried out accordance to ASTM D4719 standard.

  
Standpipe Piezometer

This test is commonly employed for the purpose of monitoring the piezometric water levels. Borehole drilled during the course of site investigations can be left open or cased if necessary to provide an observation point. The standpipe piezometer generally consists of a 25mm diameter PVC pipe with an attached Casagrande Piezometer tip at its end and installed in the completed borehole. A dipmeter is used to measure the levels of water from ground surface in the Standpipe Piezometer.

  

Surface Settlement Marker

The purpose of installing the surface settlement marker is to monitor the settlement or heaving of the ground surface.

The surface settlement marker consist of 20mm outer diameter stainless steel rod with a length of 0.50m. The steel rod is installed 0.48m into the ground with 0.02m above the ground surface.

A precision levelling and positioning apparatus (Survey equipment ) is used for the monitoring of the surface settlement marker.

  
Tiltmeter

The purpose of installation of tiltmeter is to measure and monitor the tilt of building and structures.

The tiltmeter system comprises of a Tiltplate (reference plate), Tiltmeter sensor and Data logger readout.

  
Pneumatic Piezometer

The purpose of the installation of the piezometer is to measure the dissipation of induced pore pressure and should therefore placed within the clay stratum in such a way that the reading will indicate the actual patterns of the dissipation.

The basic principle of operation of the piezometer is that a porous element is placed in soft ground so that the soil/water is continuously pressing through the pores of the element. The water collected inside the element units and the measurement of pore water pressure in the element units will determine the pore water pressure in the ground at the location of the piezometer.
Settlement Plate

The purpose of this test is to determine the surface settlement of existing ground due to filling of embankment.

The settlement plate consists of a 0.50m x 0.50m x 8mm thick mild steel base plate with a 25mm diameter GI. Pipe of 1000mm height welded in the middle of the plate. The schematic drawing of the settlement plate.

A precise leveling equipment is used for the monitoring of the settlement plate.