Introduction; General Description - Geosense VWLSS-200 Installation Manual

V1.7 January 2021

1.0 INTRODUCTION

This manual is intended for all users of Vibrating Wire Liquid Settlement System
(VWLSS-200) manufactured by Geosense and provides information on its installation,
operation and maintenance.
It is VITAL that personnel responsible for the installation and

1.1 General Description

The Vibrating Wire Liquid Settlement System (VWLSS-200) is used to monitor
settlement or heave in soils and other structures such as embankments, earth & rockfill
dams. A typical installation is shown in Figure 1, below.
The main components are a fluid reservoir, liquid filled tubing and a vibrating wire
pressure transducer, mounted on a plate or, for a borehole application, attached to an
anchor.
The vibrating wire sensor is positioned at a point where settlement is to be detected. The
pressure sensitive side of the sensor is connected to a reservoir, located on stable
ground, by two liquid-filled tubes to create a continuous fluid column. As the sensor
settles with the surrounding ground, the height of the column is increased and the
corresponding higher pressure is detected by the sensor. Settlement or heave is
calculated by converting the liquid pressure registered by the sensor, into metres of liquid
head. The sensor is fitted with a 4 core cable to obtain the pressure and temperature
readings.
Each sensor contains a Thermistor for the temperature measurement, and gas discharge
tubes for lightning protection. The system uses de-aired solution of antifreeze and water
to prevent freezing and algae growth. The system uses two liquid lines so that it could be
flushed to remove air bubbles from the system.
The effects of changes in atmospheric pressure are removed by either using a vented
transducer or mathematically, using information from another sensor.
Height of the column of liquid
increases as the cell moves down
with the settlement of the ground
Figure 1
use of this Settlement System, READS and UNDERSTANDS
this manual, prior to working with the equipment.
The VW transducer cell
measures the pressure of the col-
Single or multiple
liquid reservoir(s)
Liquid filled tubing
3