PAPAMOA EAST URBAN DEVELOPMENT PART 1 AREA LIQUEFACTION HAZARD REVIEW Technical Report

Transcription

1 PAPAMOA EAST URBAN DEVELOPMENT PART 1 AREA LIQUEFACTION HAZARD REVIEW Technical Report

2 Tauranga District Council Papamoa East Urban Development Strategy Part 1 Area Liquefaction Hazard Review Technical Report Prepared by P Brabhaharan Principal, Geotechnical Engineering & Risk Dougal Mason Engineering Geologist Opus International Consultants Limited Wellington Office Level 9, Majestic Centre 0 Willis Street, PO Box Wellington, New Zealand Telephone: Facsimile: Date: March 2006 Reviewed by Report Number SPT 2006 / 6 Dr Alexei Murashev Reference: 5C Senior Geotechnical Engineer Status: Final Doc ref: g:\localauthorities\tauranga\proj\5c _pa pamoa_east_liquefaction_hazard\report\papa moaeast_liquefaction_hazard_final.doc This document is the property of Opus International Consultants Limited. Any unauthorised employment or reproduction, in full or part is forbidden. Opus International Consultants Limited 2006

3 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review 1 Introduction Previous Study Scope of the Study Site Location Geology and Site Description Site Investigations Boreholes Static Cone Penetration Tests Laboratory Tests Ground Conditions Papamoa East Part 1 Area Future Bell Road Interchange Area Seismicity Earthquake Ground Shaking Magnitude Weighted Peak Ground Accelerations Liquefaction Hazard Definition Mechanism of Liquefaction Historical Evidence of Liquefaction Liquefaction Assessment Liquefaction Hazard Mapping Liquefaction Induced Ground Damage Conclusion References C March 2006 i

4 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review List of Figures Figure 1 Figure 2 Figure 3 Site Location Plan Locations of Site Investigations Liquefaction Hazard Map List of Appendices Appendix A Appendix B Appendix C Borehole Logs Static Cone Penetration Test Results Laboratory Test Results 5C March 2006 ii

5 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Summary The Western Bay of Plenty microzoning study report presents a regional liquefaction hazard map. This map indicates the Papamoa East Part 1 Area to have a widespread liquefaction potential, with extensive liquefaction likely in earthquake shaking levels of both % and 2% probability in 50 years. The microzoning study maps were based on only a limited amount of available information, and are meant to be used at a regional scale and recommended that site specific assessment should be undertaken for specific areas. A specific study of this Papamoa East Part 1 Area has now been carried out. This study included site specific investigations, comprising the drilling of three boreholes, 19 Static Cone Penetration Tests and some laboratory classification tests. The liquefaction hazard assessed based on the additional information indicates a generally minor to moderate liquefaction hazard for the area, with possibly widespread liquefaction along the Wairakei Stream and at the boundaries of the area. The minor liquefaction hazard generally applies to the sand hills where less than 0 mm subsidence due to liquefaction can be expected, and the moderate liquefaction hazard in inter-dunal lower lying areas, where subsidence of the order of 0 mm to 300 mm could be expected in strong earthquake shaking (return periods of 475 years and 2,500 years used in the assessment). Therefore, the study indicates a lower level of hazard from earthquake induced liquefaction, than that suggested in the microzoning study report. The liquefaction hazard at the proposed future Bell Road Interchange site remains higher and widespread liquefaction can be expected in that area. 5C March 2006 iii

6 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Tauranga City Council (The Council) is considering a District Plan change that would allow development in the Papamoa East area, see Figure 1. This would allow residential development to occur in this area. Environment Bay of Plenty has highlighted the liquefaction hazard identified in the area by the earthquake microzoning study (Opus International Consultants, 2002). The Council has commissioned Opus to review the liquefaction hazard in the area under consideration, and provide a report. The Council also requested that some additional investigations be carried out immediately southeast of the Part 1 area, to provide information for a potential interchange on Bell Road. This report presents the results from site investigations carried out for this study in Papamoa East area, the results of the assessment of liquefaction and associated ground damage from earthquakes, and a map showing the updated liquefaction hazard in the area. The Western Bay of Plenty Lifelines Study, Microzoning for Earthquake Hazards (Opus International Consultants, 2002) was carried out for the Western Bay of Plenty Lifelines Group. This study included consideration of the liquefaction hazard in the Western Bay of Plenty area, and provided regional scale maps showing the liquefaction and consequent ground damage hazards. The liquefaction hazard study map from the lifelines study indicates that the Papamoa East area under consideration for development may be prone to widespread liquefaction in moderate to large earthquakes. This indicates that liquefaction is likely to be extensive in both % and 2% probability of occurrence in 50 years (475 year and 2,500 year return periods respectively) earthquake shaking. The report also included liquefaction ground damage hazard maps, where the ground damage from liquefaction is expected to be moderate in the Papamoa East area. Moderate ground damage meant that there is the potential for large subsidence (say greater than 300 mm) in these earthquakes. However, the microzoning study maps are based on only a limited amount of available information, and are meant to be used at a regional scale. The report recommended that site specific assessment should be undertaken for specific areas. 5C March

7 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review This study comprised: Site reconnaissance of the Papamoa East Part 1 area to view the geomorphology; Site investigations comprising the drilling and logging of boreholes and Static Cone Penetration Tests; Laboratory classification tests on samples of soil recovered from the drilling; An assessment of the liquefaction hazard in the area; Map and present the liquefaction hazard. The site investigations also included some additional work at the potential interchange site, south of the Part 1 Area, see Figure 1. The Papamoa East Part 1 Area is located about 14 km east-southeast of Tauranga city centre, and 4 km east of Papamoa village. The NZMS 260 map grid reference is U The area is bound by existing development to the north and west, and open pasture to the south and east. The 1:250,000 geological map of the Rotorua region (Department of Scientific and Industrial Research, 1964) indicates the Papamoa East Part 1 Area to be underlain by dune sand and undifferentiated alluvium. The area comprises small hills (fixed sand dunes) with inter-dunal lower lying areas. The Wairakei Stream runs along the northern boundary of the site, between the Part 1 Area and the existing development along the coast. Preliminary groundwater information recorded by S&L Consultants (2005) prior to this study indicates the groundwater level to be generally between 1 m and 4 m depth below the ground surface. 5C March

8 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review 6.1 Scope and Location Site investigations, comprising 19 static Cone Penetration Tests (CPT) and the drilling of three boreholes, were carried out from the 22 nd to the 27 th of February These were followed by laboratory classification tests on samples recovered from the boreholes. Access to the western part of the site was not available, and hence was not investigated. The site investigations at the Part 1 Area and the proposed Bell Road Interchange sites are summarised in Table 1. Table 1 - Site Investigations for the Part 1 Area and proposed Bell Road Interchange Area Boreholes Static Cone Penetration Tests Papamoa East Part 1 Area BH and BH CPT to CPT Proposed Bell Road Interchange Site BH CPT to CPT 6.2 Boreholes Three boreholes (BH to BH) were drilled by Perry Drilling Ltd between 22 and 27 February The locations of the boreholes are shown on Figure 2. Standard Penetration Tests (SPT) were carried out in accordance with NZS 4402 : 1988 (Standards New Zealand, 1988) during drilling, at 1.5 m depth intervals. Standpipe piezometers were installed in each of the three boreholes to allow monitoring of the groundwater levels. Table 2 lists the depths of the boreholes, and the depths to which standpipe piezometers were installed. Table 2 - Summary of Boreholes Borehole No Easting (NZ Map Grid) Northing (NZ Map Grid) Depth of Borehole Depth of Base of Standpipe BH m 6.0 m BH m 6.0 m BH m 12.0 m Bulk samples, core samples and samples from SPT tests were collected during the drilling of the boreholes, and were logged by an engineering geologist from Opus. The engineering geological logs of the boreholes are presented in Appendix A. 5C March

9 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review 6.3 Static Cone Penetration Tests The Static Cone Penetration Tests (CPT) were carried out by Opus (Hamilton Laboratory) from 22 to 24 February Nineteen CPTs (CPT to CPT) were carried out across the site at locations shown on Figure 2. The CPTs were carried out to a depth of 20 m or a cone resistance of 30 MPa. A summary of the depths and groundwater levels at each CPT is provided in Table 3. Table 3 - Summary of Static Cone Penetration Tests Test No Easting (NZ Map Grid) Northing (NZ Map Grid) Penetration Depth Depth to Ground Water Level* CPT m 0.8 m CPT m 0.6 m CPT m 0.4 m CPT m 5.0 m CPT m 7.5 m CPT m 4.0 m CPT m 4.0 m CPT m 3.0 m CPT m 4.0 m CPT m 2.0 m CPT m 1.3 m CPT m 4.0 m CPT m 2.5 m CPT m 3.2 m CPT m 3.8 m CPT m 5.2 m CPT m 4.0 m CPT m 6.5 m CPT m 1.8 m * Based on porewater pressure measurements 5C March

10 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review The results of the CPTs are available in electronic format, and results of the tests are included in Appendix B. 6.4 Laboratory Tests Soil classification tests were carried out on five samples recovered from the boreholes by Opus (Tauranga and Hamilton Laboratories). A summary of the tests carried out on the samples is given in Table 4. Table 4 - Summary of Laboratory Soil Classification Tests Borehole No Depth Material Test Undertaken BH 2.0 m SAND Particle size distribution.0 m SAND with silt Particle size distribution 2.5 m SAND Particle size distribution BH 7.5 m SAND Particle size distribution 18.0 m clayey SILT Particle size distribution & Atterberg Limits The results of the laboratory classification tests are presented in Appendix C, and summarised in Table 5. Table 5 - Summary of Laboratory Classification Tests Borehole No Depth Material Particle Size Distribution (%) Clay Silt Sand Gravel Plasticity Index (%) BH 2.0 m SAND with silt m SAND m SAND BH 7.5 m SAND m clayey SILT C March

11 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review 7.1 Papamoa East Part 1 Area The site investigations carried out in the Papamoa East Part 1 area indicate the ground conditions to comprise predominantly medium dense sand with some loose and some dense layers, over the upper 20 m depth, see borehole logs in Appendix A and Static Cone penetration Test results in Appendix B. A shallow near surface silt layer was encountered to up to 3 m depth in borehole BH and CPTs (CPT 1 to CPT 3). A silty clay layer below about 15 m depth was penetrated in borehole BH and some CPTs (e.g., CPT1, CPT, CPT). There are a greater proportion of loose sand layers indicated in some of the CPTs (CPT, 11, 12, 13, 15 and 17). These CPTs are generally located in relatively wide lower lying inter-dunal areas. 7.2 Future Bell Road Interchange Area The future Bell Road interchange is expected to be located on a low lying flat area, to the southwest of the Part 1 Area, see Figure 2. Borehole BH and Static Cone Penetration Tests CPT, CPT, CPT, CPT and CPT- 5 were located in this area, and indicated the ground conditions to comprise predominantly medium dense sand with some loose gravel layers and soft clay layers. 5C March

12 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review 8.1 Earthquake Ground Shaking Earthquake ground shaking levels in terms of peak ground accelerations for % and 2% probability of occurrence in 50 years (equivalent to 475 year and 2,500 year return periods) is presented in the microzoning for earthquake hazards study report (Opus International Consultants, 2002). Maps presenting the peak ground accelerations (PGA) for these hazard levels are presented in that report. The peak ground accelerations extracted from the report for the Papamoa East area are presented in Table 6. Table 6 - Earthquake Ground Shaking in the Papamoa East Part 1 Area Earthquake Hazard Level Peak Ground Acceleration % probability in 50 years (return period 500 years) 0.25g to 0.3g 2% probability in 50 years (return period 2,500 years) 0.35g to 0.4g *(from Opus International Consultants, 2002) The New Zealand loadings code AS /NZS 1170 requires normal structures (including single family dwellings) to be designed to a 500 year return period earthquake shaking assuming a 50 year design life. 8.2 Magnitude Weighted Peak Ground Accelerations The microzoning report also presents magnitude-weighted peak ground accelerations. The magnitude-weighted peak ground accelerations recognise that for a given peak acceleration level, a larger magnitude earthquake is of more significance for liquefaction because of its greater duration and greater strength of long-period components. For use in assessing the potential for liquefaction, the microzoning study report (Opus International Consultants, 2002) provides maps showing peak ground acceleration estimates scaled by the magnitude-weighting factors of Idriss (1985) for probabilities of exceedance of % and 2% in 50 years. Magnitude-weighting factors are used to convert PGA produced by an earthquake of magnitude M into the PGA value from a magnitude 7.5 earthquake that has equivalent effect in terms of liquefaction potential. The magnitude weighted peak ground acceleration values for Site Class or Ground Class D that is applicable for the Papamoa east area, have been extracted from these maps and are presented in Table 6. These values have been used in the liquefaction assessment. 5C March

13 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review 9.1 Definition Liquefaction includes all phenomena giving rise to a loss of shearing resistance or to the development of excessive strains as a result of transient or repeated disturbance of saturated cohesionless soils (National Research Council, 1985). The American Society of Civil Engineers (1978) give a comprehensive definition of the terms associated with liquefaction. They define liquefaction as the act or process of transforming cohesionless soils from a solid state to a liquefied state as a consequence of increased pore pressure and reduced effective stress. 9.2 Mechanism of Liquefaction Ground shaking associated with earthquakes gives rise to an increase in the porewater pressure in saturated, loose, mainly cohesionless soils, leading to earthquake induced liquefaction. In soils where the increasing porewater pressures cannot dissipate rapidly, and become equal to the overburden stress, the soil particles no longer have interparticular friction, and the soil liquefies, losing most of its strength. This state with a peak cyclic pore pressure ratio of 0%, is known as initial liquefaction. The soil is at a liquefied state. The strength of earthquake shaking has to be sufficient to cause significant increases in porewater pressures, and its duration has to be long enough for soils to reach this state. Liquefaction most commonly occurs in saturated loose sands and silty sands. These were the only soil types thought to be prone to liquefaction. Increasingly it has become apparent from observations in earthquakes that that loose sandy gravels and low plasticity sandy silts and silts also have liquefied. While soils may develop initial liquefaction, their subsequent behaviour depends on many factors such as the soil characteristics, strength and duration of shaking and layering of the soil deposits. Soft cohesive soils such as clays and silty clays do not strictly undergo liquefaction, but could nevertheless cause similar ground damage, such as lateral spreading, flow slides or failure of structures founded on them as a result of significant loss of strength due to ground shaking. Loose sands above the water table will not liquefy. However, some densification of loose dry sands could occur in earthquakes, and cause some subsidence of the ground. 9.3 Historical Evidence of Liquefaction There is no historical evidence of liquefaction in the Western Bay of Plenty study area, from past records. This could be attributed to the lack of strong earthquake shaking in the Western Bay of Plenty study area during the relatively brief recorded history of European settlement in New Zealand. However, there have been many historical records of liquefaction in New Zealand, including in the adjacent Whakatane District during the 1987 Edgecumbe Earthquake. 5C March

14 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Given the absence of historical records in the area, the liquefaction assessment has been based on consideration of the geology and ground conditions, estimated ground shaking hazards and empirical methods developed internationally for the assessment of liquefaction. 9.4 Liquefaction Assessment Approach The approach used for assessment and mapping of the liquefaction hazard is adapted from that developed by Brabhaharan (1994). This approach, tailored to suit this study, comprised : Analyses of the potential for liquefaction using state-of-the-art empirical methods, using the results of the site investigations Consideration of the geomorphology at the site investigation locations and the assessed liquefaction potential Mapping the liquefaction hazard using the point assessments and the geomorphology maps Liquefaction Analyses The liquefaction analysis was carried out using the Robertson and Wride (1998) method for liquefaction assessment, with the aid of the software Liquefypro. The method is based on empirical correlation of cyclic stress ratio and Standard Penetration Test N values or Static Cone Penetration Test cone resistances, and consideration of the values where soils liquefied and where they did not liquefy in past earthquakes. The correlations are based on a large database of records from past earthquakes. Cyclic stress ratio = a max. o. r d / o. g (1) where, a max o r d peak ground acceleration (pga) total overburden stress at the depth under consideration stress reduction factor that reduces from 1 at the ground surface o effective overburden stress at the same depth g gravitational acceleration The penetration test values were corrected for overburden pressure. The fines contents of the soils were used (where not available assumed) for the assessment from borehole and SPT records, to make allowance for the increased liquefaction resistance associated with the proportion of fines in the soils. For the assessment from CPT results, the method made allowance for fines content based on the friction ratio (ratio of sleeve friction to cone resistance which is related to the soil type). 5C March

15 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review The liquefaction hazard was assessed for the two uniform hazard levels of : % probability in 50 years (475 year return period), and 2% probability in 50 years (2,500 year return period). Magnitude-weighted peak ground accelerations, derived as discussed in Section 8.2, were used in the liquefaction analysis to account for the contribution from a variety of earthquake events with different magnitudes. This enabled the magnitude of the earthquakes and hence the duration of ground shaking to be taken into consideration. The assessment enabled an assessment of the thickness and depth of the soil horizons likely to liquefy at each investigation location. An assessment of the possible ground subsidence likely as a result of liquefaction was also assessed using the method of Ishihara and Yoshimine (1992). The liquefaction assessment gave point estimates of the potential for liquefaction and the associated magnitude of subsidence in the two levels of earthquake shaking, at each site investigation location. The liquefaction potential was classified into five classes in the microzoning study (Opus International Consultants, 2002), as set out in Table 7. Table 7 - Liquefaction Potential Classes Class Liquefaction Potential Description 1 No Liquefaction Liquefaction unlikely in any scenario, except locally such as stream deposits or fill. 2 Localised liquefaction Liquefaction is generally unlikely but there may be limited areas that are likely to liquefy in a large earthquake event. 3 Minor Liquefaction No liquefaction likely in a % in 50 year pga, but liquefaction of limited layers may occur in a larger 2% in 50 year earthquake event. 4 Moderate Liquefaction Liquefaction is likely in both % and 2% in 50 year pga, in localised areas or are associated with limited ground damage. 5 Extensive Liquefaction Liquefaction is likely to be extensive in both % and 2% in 50 year pga and could lead to significant ground damage. The liquefaction analysis indicates that there is a potential for liquefaction of only some limited layers of sand in a significant proportion of the CPT and borehole locations at the Papamoa East Part 1 Area. At these locations, the subsidence due to liquefaction is expected to be minor at less than 0 mm. This is classified as Class 3, Minor Liquefaction, see Table 7. These locations generally are on the sand hills. 5C March 2006

16 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review However, at some CPT locations (CPT, 11, 12, 13, 15 and 17), a greater thickness of sand is likely to liquefy in the two levels of shaking considered. This is expected to lead to a moderate amount of subsidence of about 0 mm to 300 mm. This is classified as Class 4 Moderate Liquefaction, see Table 7. These locations are generally wide low lying areas between the sand hills. The liquefaction at the future proposed Bell Road interchange area, see Figure 2, is likely to be extensive in both earthquake levels considered, with liquefaction of a significant thickness of the ground indicated by the analysis. This is expected to lead to large subsidence exceeding 300 mm. This is classified as Class 5 Extensive Liquefaction, see Table 7. This occurs in the flat low lying area where the proposed interchange will be located. 9.5 Liquefaction Hazard Mapping The areal extent of liquefaction hazard was then mapped by considering the assessed point estimates of liquefaction potential, at each site investigation location, and the geographical spread of the point estimates and the geomorphology of the area. The liquefaction potential has been mapped using the five classes in Table 7. These geomorphological characteristics have been used to map the liquefaction hazard over the whole Part 1 Area including the western portion that was inaccessible for carrying out site investigations. The liquefaction hazard is generally: minor in the sand hills, moderate in the wide lower lying valleys between the sand hills, and extensive on the low lying flat plain. The liquefaction hazard is extensive in which the proposed future Bell Road Interchange will be located. It is also probable that the liquefaction hazard could be extensive along the Wairakei Stream at the northern boundary of the Part 1 Area. The liquefaction hazard was mapped based on the above characteristics and the geomorphology of the area identified from the site reconnaissance and aerial photographic and contour maps. A liquefaction hazard map has been prepared with the aid of a geographical information system, and is presented as Figure 3, at a scale of 1 : 20,000. 5C March

17 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review 9.6 Liquefaction Induced Ground Damage Consequences of Liquefaction Liquefaction can lead to the following effects, that can cause damage to infrastructure, buildings, lifelines and related facilities : Ground damage subsidence, lateral spreading, flow failure, slope failure Bouyancy of buried services, tanks and chambers (manholes) Foundation failure due to reduction / loss of bearing capacity Settlement of structures on liquefied materials Liquefaction Induced Ground Damage Liquefaction can lead to ground damage in the form of subsidence, failure of sloping ground, flow failure and lateral spreading of ground towards natural banks and embankments built on liquefiable ground. The presence of a surface layer that is resistant to liquefaction could reduce the ground damage at the surface due to the liquefaction of underlying layers. However, where lateral spreading is likely, the presence of a nonliquefiable layer may not preclude ground damage. The actual ground damage will depend on the properties of the liquefiable soils, their thickness, and the topography of the area. The possible ground damage has been assessed based on the subsidence analysis discussed in Section 9.4.2, literature and engineering judgement. Ground subsidence has been assessed based on the method of Ishihara and Yoshimine (1992) as discussed in Section The subsidence estimates range from less than mm to over 500 mm. These are very approximate estimates only. Indicative magnitudes of ground subsidence for the different liquefaction potential classes in a % in 50 year earthquake shaking are given in Table 8. Table 8 - Liquefaction Induced Subsidence Class Liquefaction Potential Order of Magnitude of Subsidence 1 No Liquefaction None. 2 Localised liquefaction Variable, but likely to be small. 3 Minor Liquefaction Less than 0 mm. 4 Moderate Liquefaction 0 mm to 300 mm. 5 Extensive Liquefaction Greater than 300 mm, and possibly over 00 mm in places. 5C March

18 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Lateral spreading could occur along river / stream banks and coastal areas, where the liquefied ground could displace towards the free surface. Any embankments or bridge abutments built on liquefiable ground are also likely to be affected. The simple rules given in Table 9 were developed by Brabhaharan and Thrush (2003) to provide an indication of the degree and extent of liquefaction induced lateral spreading, recognising that the extent damage could be variable. Table 9 - Liquefaction Induced Lateral Spreading Assumptions Liquefaction Potential Class Distance from bank / shore % in 50 years 2% in 50 years 1 No liquefaction ground damage 2 and 3 No significant ground damage or uncertain 4 5 Within 50 m Significant ground damage Extensive ground damage 50 m to 0 m Minor ground damage Significant ground damage Within 50 m Extensive ground damage Extensive ground damage 50 m to 200 m Significant ground damage Significant ground damage Notes: Ground deformation definitions Minor s of millimetres to 200 mm Significant 0s of millimetres to 1 metre Extensive metres While these rules are approximate only, they could provide a basis for identifying areas where lateral spreading damage needs to be considered. In the Papamoa East Part 1 Area, lateral spreading could be experienced in the vicinity of the Wairakei Stream. The liquefaction assessment has been carried out as an area-wide hazard assessment based on the available information. It should not be considered as a substitute for sitespecific site investigations and geotechnical engineering assessment for any development. While the zones of liquefaction potential have been shown on the map, there is no certainty of liquefaction in a particular area due to an earthquake of any size. The classification liquefaction potential is indicative only, and does not imply any level of damage to particular structures or lifelines. 5C March

19 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review The magnitudes of ground damage suggested in the report are indicative only. The boundaries of the various liquefaction zones are approximate only based on the geomorphology and should be used with caution. Site specific consideration should be given for the performance at a particular site. The development of the Papamoa East Part 1 Area may comprise bulk earthworks to form building platforms and landscaping. Earthworks for example may comprise the lowering of sand hills and filling of lower lying inter-dunal areas. The effects of liquefaction on development in lower lying areas are expected to be somewhat reduced if a layer of dense engineered fill is placed to raise these areas. The lowering of sandhills may expose the development to liquefiable layers near the lowered ground surface. Such layers could be compacted given the small thicknesses of liquefiable layers or the limited effects of such liquefaction can be taken into consideration in the design of the development. Given the minor to moderate level of liquefaction hazard, low rise residential and light commercial development could be suitably developed by taking simple measures to limit potential damage from the limited liquefaction hazard in the area. Consideration may be given to adapting the layout of any development to avoid any sensitive structures in the areas of moderate liquefaction hazard. 5C March

20 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review The Western Bay of Plenty microzoning study report presents a regional liquefaction hazard map indicating the Papamoa East Part 1 Area to have a widespread liquefaction potential, with extensive liquefaction likely in both % probability of occurrence in 50 years and 2% probability of occurrence in 50 years level earthquake shaking. However, the maps are based on only a limited amount of available information, and are meant to be used at a regional scale and recommended that site specific assessment should be undertaken for specific areas. A specific study of this Papamoa East Part 1 Area indicates a generally minor to moderate liquefaction hazard for the area, with widespread liquefaction along the Wairakei Stream and at the boundaries of the area, in the % and 2% probability of occurrence levels of earthquake shaking (475 year and 2,500 year return periods). The minor liquefaction hazard generally applies to the sand hills where less than 0 mm subsidence can be expected, and the moderate liquefaction hazard applies to the inter-dunal lower lying areas, where subsidence of the order of 0 mm to 300 mm could be expected. Therefore, the study indicates a lower level of hazard from earthquake induced liquefaction, than that suggested in the microzoning study report. The liquefaction hazard at the proposed future Bell Road Interchange site remains higher and widespread liquefaction can be expected in that area. 5C March

21 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Brabhaharan, P, Hastie, W J, and Kingsbury, P A (1994). Liquefaction hazard mapping techniques developed for the Wellington Region, New Zealand. Annual NZNSEE Conference, Wairakei, 18 March Brabhaharan, P and Thrush, J (2003). Liquefaction Hazards in the Western Bay of Plenty. Geotechnics on the Volcanic Edge. NZ Geotechnical Society Symposium, Tauranga, New Zealand, 260 March Department of Scientific and Industrial Research (1964). Healy, J, Schofield, JC and Thompson, BN. Sheet 5 Rotorua (1st Ed.). Geological Map of New Zealand 1 : 250,000, Wellington. Idriss, I.M. (1985). Evaluating seismic risk in engineering practice. Proceedings of the 11th International Conference of Soil Mechanics and Foundation Engineering, San Francisco, USA, 1: Ishihara, K and Yoshimine, M (1991). Evaluation of Settlements in Sand Deposits following Liquefaction during Earthquakes. Soils & Foundations 32, No 1, pp1738. Opus International Consultants (2002). Microzoning for Earthquake Hazards for the Western Bay of Plenty. Prepared by Brabhaharan, P, Thrush, J, Wood, P, Dellow, GD, McVerry, G, Lynch, R, Dennison, D of Opus International Consultants and the Institute of Geological & Nuclear Sciences. Wellington, 4 p. Robertson, PK and Wride, CE (1998). Cyclic liquefaction and its evaluation based on the SPT and CPT. Proceeding of the NCEER Workshop on Evaluation of Liquefaction Resistance of Soils, Salt Lake City, USA: 418. S & L Consultants (2005). Groundwater level records. Standards New Zealand (1988). NZS 4402 : Methods of Testing Soils for Civil Engineering Purposes. 5C March

22 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Figures 5C March 2006

23 N E W S Title: Project: Job No: Date: Figure: 5C March Site Location Plan Papamoa East Urban Development Strategy Part 1 Area - Liquefaction Hazard Review Prepared for: Prepared by: Study Area Papamoa East Part 1 Bell Road Interchange Mt Maunganui TAURANGA Te Puke m E 28000m E m N Motiti Island Papamoa Kilometers LEGEND m N m E Papamoa East Part 1 Area Bell Road Interchange

24 N W E S $ CPT17 CPT16 $ $ BH3 CPT15 $ CPT14 $ CPT13 $ CPT12 $ CPT8 LEGEND Cone Penetration Tests Bore Holes Study Area Papamoa East Part 1 Bell Road Interchange $ $ CPT11 $ CPT $ BH2 CPT9 $ $ CPT1 $ CPT2 CPT7 $ $ $ CPT6 $ CPT4 CPT3 BH1 CPT5 $ $ CPT18 CPT19 Title: Project: Prepared for: Locations of Site Investigations Papamoa East Urban Development Strategy Part 1 Area - Liquefaction Hazard Review Prepared by: Kilometers Job No: 5C Date: March 2006 Figure: 2

25 W N S E IMPORTANT NOTES Accompanying Report This map should be used in conjunction with the report "Papamoa East Urban Development - Part 1 Area Liquefaction Hazard" (Opus International Consultants, 2006). Limitations The zone boundaries on this map are approximate only and have been determined with the aid of the geomorphology, regional geological maps and available borehole and Static Cone Penetration Test data. The classification of the liquefaction hazard is indicative only, and the level of damage to any facility will depend on a variety of factors such as the potential for liquefaction, the thickness and depth of liquefying layers and their relationship to other layers, and the topography and the nature of the facility itself. Further limitations are given in the report. Localised areas of enhanced hazard may be present within areas identified as having a low hazard, and also the hazard may be lower in some sections identified as having a high hazard. Site-specific assessment of the hazard based on site-specific investigations and risk should be considered for assessing the performance or design of a specific facility. LEGEND Study Area Papamoa East Part 1 Bell Road Interchange Liquefaction Hazard No Liquefaction Localised Liquefaction Minor Liquefaction Moderate Liquefaction Widespread Liquefaction Liquefaction unlikely in any scenario, except locally such as stream deposits or fill. Liquefaction is generally unlikely but there may be limited areas that are likely to liquefy in a large earthquake event. Minor liquefaction likely in a % in 50 year earthquake shaking, and liquefaction of some layers may occur in a larger 2% in 50 year earthquake event Liquefaction is likely in both % and 2% in 50 year earthquake shaking, in localised areas or are associated with limited ground damage Liquefaction is likely to be extensive in both % and 2% in 50 year earthquake shaking and could lead to significant ground damage Title: Liquefaction Hazard Map Project: Papamoa East Urban Development Strategy Part 1 Area - Liquefaction Hazard Review Prepared for: Prepared by: Kilometers Job No: Date: Figure: 5C March

26 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Appendix A Borehole Logs 5C March 2006

27

28

29

30

31

32

33

34

35

36 Papamoa East Urban Development Strategy : Part 1 Area : Liquefaction Hazard Review Appendix B Static Cone Penetration Test Results 5C March 2006

37 Cone resistance in MPa (qc) Friction ratio in % (Rf) Sleeve friction in MPa (fs) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 1/14

38 Dynamic pore pressure in MPa (u) Equilibirum pore pressure in MPa (uo) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 2/14

39 Corrected cone resistance in MPa (qt) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 3/14

40 Excess pore pressure in MPa (du) Dynamic pore pressure ration in MPa (u/qc) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 4/14

41 Effective cone resistance in MPa (qe) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 5/14

42 Total vertical stress in kpa (rov;z) Effective vertical stress in kpa (rov;z`) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 6/14

43 Net cone resistance in MPa (qn) Pore pressure ratio in % (Bq) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 7/14

44 Normalised cone resistance in MPa (qnorm) Normalised local friction in % (fnorm) > Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 8/14

45 Soil behaviour type index (Ic) Kiezelachtig zand Zandsoorten Zand Slib mengsels mengsels Kleisoorten Organische grond Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 9/14

46 Undrained shear strength in kpa (Su) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 /14

47 Relative density (consolidated) in % Relative density (over-consolidated) in % Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 11/14

48 Equivalent SPT N60 Value Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 12/14

49 Soil Classification Soil (Qt,Fr) Soil (Qt,Bq) Soil (Avarage) (0) not defined (0) not defined (0) not defined (3) clays-clay to silty clay (3) clays-clay to silty clay (3) clays-clay to silty clay (7) gravelly sand to sand Depth in m below ground level (G.L.) (3) clays-clay to silty clay (2) organic soils-peats (3) clays-clay to silty clay (3) clays-clay to silty clay (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (5) sand mixtures (4) clayey silt to silty clay (0) not defined (0) not defined (0) not defined (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (3) clays-clay to silty clay (0) not defined (4) clayey silt to silty clay (3) clays-clay to silty clay (5) sand mixtures (3) clays-clay to silty clay (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (5) sand mixtures (3) clays-clay to silty clay (5) sand mixtures (3) clays-clay to silty clay (3) clays-clay to silty clay 0 = not defined 1 = sensitive, fine grained 2 = organic soils-peats 3 = clays-clay to silty clay 4 = clayey silt to silty clay 5 = sand mixtures 6 = sands 7 = gravelly sand to sand 8 = very stiff sand to clayey sand 9 = very stiff fine grained Date : 2306 Cone no. : CCFIP.C97 0, 0 CPT no. : 01 13/14

50 Internal friction angle in Date : 2306 Cone no. : CCFIP.C97 CPT no. : 01 14/14

51 Cone resistance in MPa (qc) Friction ratio in % (Rf) Sleeve friction in MPa (fs) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 1/14

52 Dynamic pore pressure in MPa (u) Equilibirum pore pressure in MPa (uo) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 2/14

53 Corrected cone resistance in MPa (qt) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 3/14

54 Excess pore pressure in MPa (du) Dynamic pore pressure ration in MPa (u/qc) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 4/14

55 Effective cone resistance in MPa (qe) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 5/14

56 Total vertical stress in kpa (rov;z) Effective vertical stress in kpa (rov;z`) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 6/14

57 Net cone resistance in MPa (qn) Pore pressure ratio in % (Bq) > Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 7/14

58 Normalised cone resistance in MPa (qnorm) Normalised local friction in % (fnorm) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 8/14

59 Soil behaviour type index (Ic) Kiezelachtig zand Zandsoorten Zand Slib mengsels mengsels Kleisoorten Organische grond Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 9/14

60 Undrained shear strength in kpa (Su) E003 -> Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 /14

61 Relative density (consolidated) in % Relative density (over-consolidated) in % Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 11/14

62 Equivalent SPT N60 Value Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 12/14

63 Soil Classification Soil (Qt,Fr) Soil (Qt,Bq) Soil (Avarage) (7) gravelly sand to sand (5) sand mixtures (5) sand mixtures (7) gravelly sand to sand (7) gravelly sand to sand (7) gravelly sand to sand (7) gravelly sand to sand Depth in m below ground level (G.L.) (4) clayey silt to silty clay (3) clays-clay to silty clay (2) organic soils-peats (3) clays-clay to silty clay (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (5) sand mixtures (4) clayey silt to silty clay (4) clayey silt to silty clay (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (5) sand mixtures (4) clayey silt to silty clay (0) not defined (4) clayey silt to silty clay (0) not defined (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (5) sand mixtures (3) clays-clay to silty clay (3) clays-clay to silty clay (5) sand mixtures (3) clays-clay to silty clay (5) sand mixtures (3) clays-clay to silty clay (5) sand mixtures (3) clays-clay to silty clay (3) clays-clay to silty clay (0) not defined (5) sand mixtures (3) clays-clay to silty clay (3) clays-clay to silty clay (7) gravelly sand to sand 0 = not defined 1 = sensitive, fine grained 2 = organic soils-peats 3 = clays-clay to silty clay 4 = clayey silt to silty clay 5 = sand mixtures 6 = sands 7 = gravelly sand to sand 8 = very stiff sand to clayey sand 9 = very stiff fine grained Date : 2306 Cone no. : CCFIP.C97 0, 0 CPT no. : 02 13/14

64 Internal friction angle in Date : 2306 Cone no. : CCFIP.C97 CPT no. : 02 14/14

65 Cone resistance in MPa (qc) Friction ratio in % (Rf) Sleeve friction in MPa (fs) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 1/14

66 Dynamic pore pressure in MPa (u) Equilibirum pore pressure in MPa (uo) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 2/14

67 Corrected cone resistance in MPa (qt) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 3/14

68 Excess pore pressure in MPa (du) Dynamic pore pressure ration in MPa (u/qc) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 4/14

69 Effective cone resistance in MPa (qe) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 5/14

70 Total vertical stress in kpa (rov;z) Effective vertical stress in kpa (rov;z`) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 6/14

71 Net cone resistance in MPa (qn) Pore pressure ratio in % (Bq) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 7/14

72 Normalised cone resistance in MPa (qnorm) Normalised local friction in % (fnorm) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 8/14

73 Soil behaviour type index (Ic) Kiezelachtig zand Zandsoorten Zand Slib mengsels mengsels Kleisoorten Organische grond Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 9/14

74 Undrained shear strength in kpa (Su) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 /14

75 Relative density (consolidated) in % Relative density (over-consolidated) in % Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 11/14

76 Equivalent SPT N60 Value Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 12/14

77 Soil Classification Soil (Qt,Fr) Soil (Qt,Bq) Soil (Avarage) (7) gravelly sand to sand (7) gravelly sand to sand (7) gravelly sand to sand (0) not defined (0) not defined (7) gravelly sand to sand (7) gravelly sand to sand (7) gravelly sand to sand (7) gravelly sand to sand Depth in m below ground level (G.L.) (3) clays-clay to silty clay (3) clays-clay to silty clay (3) clays-clay to silty clay (3) clays-clay to silty clay (4) clayey silt to silty clay (5) sand mixtures (4) clayey silt to silty clay (7) gravelly sand to sand (7) gravelly sand to sand (3) clays-clay to silty clay (4) clayey silt to silty clay (4) clayey silt to silty clay (5) sand mixtures (3) clays-clay to silty clay (0) not defined (4) clayey silt to silty clay (5) sand mixtures (4) clayey silt to silty clay (5) sand mixtures (5) sand mixtures (5) sand mixtures (3) clays-clay to silty clay (3) clays-clay to silty clay (3) clays-clay to silty clay (5) sand mixtures (5) sand mixtures (5) sand mixtures (5) sand mixtures (5) sand mixtures (5) sand mixtures (4) clayey silt to silty clay (3) clays-clay to silty clay (4) clayey silt to silty clay 0 = not defined 1 = sensitive, fine grained 2 = organic soils-peats 3 = clays-clay to silty clay 4 = clayey silt to silty clay 5 = sand mixtures 6 = sands 7 = gravelly sand to sand 8 = very stiff sand to clayey sand 9 = very stiff fine grained Date : 2306 Cone no. : CCFIP.C97 0, 0 CPT no. : 03 13/14

78 Internal friction angle in Date : 2306 Cone no. : CCFIP.C97 CPT no. : 03 14/14

79 Cone resistance in MPa (qc) Friction ratio in % (Rf) Sleeve friction in MPa (fs) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 1/14

80 Dynamic pore pressure in MPa (u) Equilibirum pore pressure in MPa (uo) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 2/14

81 Corrected cone resistance in MPa (qt) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 3/14

82 Excess pore pressure in MPa (du) Dynamic pore pressure ration in MPa (u/qc) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 4/14

83 Effective cone resistance in MPa (qe) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 5/14

84 Total vertical stress in kpa (rov;z) Effective vertical stress in kpa (rov;z`) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 6/14

85 Net cone resistance in MPa (qn) Pore pressure ratio in % (Bq) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 7/14

86 Normalised cone resistance in MPa (qnorm) Normalised local friction in % (fnorm) Date : 2306 Cone no. : CCFIP.C97 CPT no. : 04 8/14