Sheet Pile Construction Monitoring Methods

Sheet Pile Displacement Monitoring

1) Vertical position monitoring
Surveying use Trimble DINI12 Digital Precision  Levels and WILD NA2 + GPM3 precision optical levels. The vertical deformation point error is more than + 0.5 mm in control. To ensure the monitoring accuracy, according to the specifications in the dock construction impacts outside the security and stability, in the good visual area, they set the two elevation reference points and three point field levels, composed of vertical displacement of the control network,taking1 to 2 months once Regular individual test to  test its stability and ensure the quality of test facilities. The elevation of each monitoring point is composed of a close working standard line level loop, the vertical displacement of the monitoring points is calculated by the twice measured height difference of the monitoring points. The amount of vertical displacement is calculated to mm.

2) Horizontal displacement monitoring 
They use LeicaTC402 Total Station and the United States Ashtech Z-survey dual-frequency GPS receiver. Benchmark test for the monitoring network together once a month. Monitoring point observation use the measured edge intersection, the intersection angle controls between 60 ° ~ 120 °. Monitoring point’s prism used to force the final heart devices to boost the accuracy. Deformation point relative to the operating point of the position error control ≤ ± 2.0 mm.

The horizontal displacement of monitoring points is calculated by the difference between two measured data. The amount of horizontal displacement is to mm.

Sheet Pile Deformation (inclinometer) Monitoring
Steel sheet pile and the soil type inclinometer and domestic use U.S. Geokon603 CN-1-type inclinometer, bottom-up by 1.0 m equidistant measurement, automatic storage records, forward-backward two readings of 180 ° observed.  To ensure the accuracy of observation, each measurement, the test sensor isto be placed in the bottom of the hole to 10 ~ 15 min, to ensure that the temperature balance. Monitoring the value of precision is ± 0.1 mm.

Stresses and Pressure Monitoring
The test of stresses, earth pressure, pore water pressure use the domestic XP05-type vibrating wire frequency (temperature) readout and XP99-type vibrating wire multi-frequency instrument, taking the readings and automatic direct-reading.Thereading accuracy  is ± 0.5Hz, ± 0.5 ℃.. Monitoring accuracy: steel sheet pile stress is ± 0.01 Mpa and earth pressure is± 1 Kpa and pore water pressure value is± 1 Kpa.

Groundwater Monitoring
The underground water level observation use SWJ-8090 type selection of domestic electricity type ruler over the two DaXun and typhoon period. Practice has proved that the water level gauge to monitor selected to take direct readings, the smallest ruler depicts 1 mm. Monitoring methods is appropriate and monitoring points layout is reasonable and the value of the sensor accuracy is ± 2 mm. Scale design and observational accuracy are to meet the requirements of the project, playing a guiding role in the construction.

Underwater Slope Stability Monitoring
Underwater slope stability monitoring uses U.S. AshtechZ-survey, based on the monitoring of large-span steel sheet pile cofferdam works double frequency GPS receivers with choke-type antenna with domestic HY1700 bathymetric features, increasing the lateral earth pressure of steel sheet pile, inside and outside the row of steel sheet pile deformation detection instrument on board operations, automatic continuous record storage measuring with the stress changes of the standards supporting  process  and pore-water pressure outside the cofferdam and the steel rod depth rod method. The former measurement accuracy≤±the stress and guide beam stress. Monitoring, testing is very comprehensive The latter accuracy ≤ ± 5 cm, similar to hydraulic engineering at home and abroad is rare.