EQC is investigating new land strengthening methods for properties such as those in TC3 that are prone to liquefaction (see EQC article New Earthquake Simulator in Canterbury). The methods being trialled include:

Rapid Impact Compaction: Rapid ground compaction using a hydraulic ram attached to a digger.
Rammed Aggregate Piers: Drilling into the ground, filling the holes with gravel, and then compacting the gravel with a hydraulic ram.
Low Mobility Grout: Injecting a cement-based grout into the ground under pressure to form a series of underground pillars.
Horizontal Soil Mixing: Directional drilling beneath a structure to mix cement into the soil and create horizontal beams.

This page will provide previews of three groups of figures containing the results from the testing. The initial release gives the site layouts and most of the pre-trial test results. The geophysical test results, namely P and S wave velocities, will be added in early August and the dynamic test results from the T-Rex testing, namely strain and porewater pressure responses, will be added later in August.

The figures published on this page provide a preliminary preview the test programme data. While the figures have had quality checks, they are a preliminary release only. Figure content and numbering may change as analysis and reporting progresses or further figures are added to this page.

Trial Area Layouts (Figure Series 1)

The Trial Area Layout figure series shows the relative positions of the trial, test and practice areas (Figures 1A3, 1A4, and 1A6). Detailed maps of each of these areas show the locations of the ground improvements along with pre and post ground improvement CPT (Figures 1B3, 1C3, etc.). The detail figures also summarise construction details and tabulate the locations, applied hammer drop heights, blow counts and penetration depths for the CPT.

The investigation, ground improvement and sensor locations were surveyed using dGPS equipment. Material volumes, distances, construction times and other information tabulated within the figures from measurements recorded by instruments within or supporting the installation equipment may imply greater accuracy or precision than the instruments calibration, but the supplied information is recorded in these figures to allow relative comparisons.

Pre Improvement CPT within T-Rex Testing Area (Figure Series 2)

The CPT profiles from before the ground improvements (Figures 2F) show the CPT tip resistance and friction ratio, the inferred Soil Behaviour Type Index (Ic) and the estimated fines content. The measured P and S wave velocities are plotted alongside the CPT profiles. The potential to liquify was estimated for the profile using the Idriss and Boulanger (2008) method. Profiles of the potential to liquify with Peak Ground Accelerations (PGA) of 0.13 g, 0.20 g and 0.35 g (all for a M7.5 earthquake) are plotted alongside the CPT profiles. Groundwater level records and a key showing the trial panel layout and investigation locations are also included in the figures.

Pre Improvement SWS within T-Rex Testing Area (Figure Series 3)

The SWS profiles from before the ground improvements (Figures 3F) show the SWS revolution count profiles at CPT and test panel locations. The Figure Series 2 CPT tip resistance and profiles of the potential to liquify with Peak Ground Accelerations (PGA) of 0.13 g, 0.20 g and 0.35 g (all for a M7.5 earthquake) are plotted alongside the SWS profiles. Groundwater level records and a key showing the trial panel layout and investigation are also included in the figures.

Post Improvement CPT Comparisons (Figure Series 4, 5 & 6)

The CPT profiles from before the ground improvements and a nominal 5, 14 and 28 days after the improvements (Figures 4, 5 and 6) show the CPT tip resistance and friction ratio, the inferred Soil Behaviour Type Index (Ic), and the Cyclic Resistance Ratio (CRR) calculated using the Idriss and Boulanger (2008) method for each of the CPT. A profile of the estimated Idriss and Boulanger potential to liquify is plotted for Peak Ground Accelerations (PGA) of 0.13 g, 0.20 g and 0.35 g (all for a M7.5 earthquake) alongside the CPT profiles. The average CRR less than CRR = 2 in the profile depths between 1.0 and 2.5 m and between 2.5 and 4.0 m are also plotted with distance from the ground improvement.

Figures

IMPORTANT NOTICE

This data was prepared or compiled for The Earthquake Commission (EQC) to assist in assessing insurance claims made under the Earthquake Commissions Act 1993. It was not intended for any other purpose. EQC and its engineers, Tonkin & Taylor, have no liability to any user of this data or for the consequences of any person relying on them in any way. The data is made available solely on the basis that:

Any Database User has read and agrees to the Terms of Use for the Database;
Any Database User has read any explanatory text accompanying the Data; and
The "Important Notice" accompanying the data must be reproduced wherever the data is reproduced.

This project has many similar types of figure so the figure numbers finish with a site/area/panel identifier and a site number to provide a more convenient referencing system.

Site/Area/Panel Identifier		Site Number
Letter	Area or Panel Description	Site	Location
A	Site Overview (showing the five areas)	3	Wainoni
B	Rapid Impact Compaction (RIC) Spacing trial area	4	Avondale
C	Rammed Aggregate Piers (RAP) Spacing trial area	6	Bexley
D	Low Mobility Grout (LMG) Spacing trial area
E	Horizontal Mixing (HM) Practice area
F	T-Rex Testing area (showing investigation panels)
G	T-Rex Testing area (As-built summary)
H	Rapid Impact Compaction (RIC) Investigation panel
I	Rammed Aggregate Piers (RAP) Investigation panel
J	Low Mobility Grout (LMG) Investigation panel
K	Horizontal Mixing (HM) Investigation panel 1
L	Horizontal Mixing (HM) Investigation panel 2

Figure Series	Site 3 (Wainoni)			Site 4 (Avondale)			Site 6 (Bexley)
Figure Series	RIC	RAP	LMG	RIC	RAP	LMG	RIC	RAP	LMG
1. Trial Area Layouts	Figures 1A3 to 1L3			Figures 1A4 to 1J4			Figures 1A6 to 1L6
2. Pre Improvement CPT	Figure 2F2			Figure 2F4			Figure 2F6
3. Pre Improvement SWS	Figure 3F3			Figure 3F4			Figure 3F6
4. 5 Day Post Improvement CPT	-	Fig 4C3	-	-	Fig 4C4	-	-	-	-
5. 14 Day Post Improvement CPT	Fig 5B3	-	Fig 5D3	Fig 5B4	-	Fig 5D4	Fig 5B6	Fig 5C6	Fig 5D6
6. 28 Day Post Improvement CPT	Fig 6B3	Fig 6C3	Fig 6D3	Fig 6B4	Fig 6C4	Fig 6D4	Fig 6B6	Fig 6C6	Fig 6D6

Reference

Idriss, I.M. & Boulanger, R.W. (2008). Soil liquefaction during earthquakes, MNO-12, Earthquake Engineering Research Institute, 242p