Subsurface Compacted Rubble Raft (SCRR) Technology for Ground Improvement

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1 Subsurface Compacted Rubble Raft (SCRR) Technology for Ground Improvement Zhaodong Du & Dr Mohamed Shahin Curtin University, Perth WA 6845, Australia 1

2 Index Preface What is SCRR? SCRR Mechanism & Construction SCRR Advantages & Limitations Design & Quality Control Further Research Conclusion 2

3 Preface 1. House on Bamboo raft on water (Kirill Cherezov, 2016) ( 2. House on gravel raft on problematic ground ( inforced%20gravel%20rafts.pdf, 2016) 4. How about a subsurface raft? 3. Submarine floats on water, & hovers in water (2016, It can, only if it is economic, environment friendly, & technically make senses. 3

4 Work Sample Liquefaction Damage Removed! Figure 1. Liquefaction analysis overall plots. 4

What is SCRR? New acquaintance: Subsurface Compacted Rubble Raft. Continuous robust rubble cuboid underground. Patent Technology for Ground Improvement (NZ Patent 714011 by Z. DU).

5 What is SCRR? New acquaintance: Subsurface Compacted Rubble Raft. Continuous robust rubble cuboid underground. Patent Technology for Ground Improvement (NZ Patent by Z. DU). Primary purpose: solving liquefaction problems. Figure 2. Rubble cuboid underground Two Major Uses: eliminate reverse effects of problematic soils: e.g. liquefaction, weak, clay. Provide a layer with much higher bearing capacity 5

6 What is SCRR? SCRR Bases & References: Christchurch rebuild work experience across 550 sites: Approximately 980 CPT tests, 420 Scala tests, 200 HA, 150 sites mapping, and 30 investigation reports and foundation solutions designs Mature theory of CRUST (Ishihara 1985) Figure 3: surface un-liquefiable layer & underlying liquefiable sand layer (Ishihara 1985). Practices: Compacted gravel raft foundations (NZGS 2015) Raft Structure & functions Surface dynamic compaction Huge Compaction energy. FRANKI piles (Franki Foundations Group 2015) large subsurface bases. Bearing Base piles (Mr Jizhong Wang 1998) Demolition rubbles use and bases. Stone Columns (Germany 1950s) Bottom compaction and bases. 6

7 SCRR STURCTURE & FORMATION SCRR Construction: an underground dynamic compaction Franki piling - bottom formation Stone column - bottom formation Similar to: base bearing piling - bottom formation Compacted sand pier - bottom formation Procedure consists of 7 steps (Fig. 4). Figure 4. Procedure to create a SCRR bulb (adapted from Franki Foundations Group 2015, Qi 2007). 7

SCRR Structure & Formation SCRR: an integrity of a number of SCRR bulbs (or units), Every bulb = a compacted rubble zone + a densified soil zone Each bulb consumes rubbles at 1.5 to 2 m 3 (D=1.42~1.

8 SCRR Structure & Formation SCRR: an integrity of a number of SCRR bulbs (or units), Every bulb = a compacted rubble zone + a densified soil zone Each bulb consumes rubbles at 1.5 to 2 m 3 (D=1.42~1.56 m). Thickness of a single layer of jointed bulbs is about m. Figure 5. SCRR bulb structure. Figure 6. Cross section of two bulbs. Bulb intervals: m. 2 bulbs strongly joint rubble to rubble/very dense common soil. 8

9 SCRR Structure & Formation SCRR Structure: A four-bulb pyramid structure. Figure 7. left: the base of 3 bulbs. right: a four bulb pyramid structure. A site may require 1 ~ 3 layer structure. Mostly 2-layer structure: 1st layer is the framework, 2 nd /3 rd for reinforcement 9

10 SCRR Structure & Formation Surface Ram-compaction Influence Depth Menard & Broise (Bo et al., 2009) equation: D: D = n (w h) ½ (1) SCRR compaction at hole bottom in depth, D = 0.5 (4 5) ½ = 2.2 m. Improvement effect of liquefiable soils by in-situ test, Tongxian, Beijing Table 1 Soil SPT readings before & after compaction (adapted from Yang & Wang 2012). Bore hole Test depth (m) SPT critical blows, n SPT, n before compaction SPT, n after compaction Liquefaction potential before Liquefaction potential after SPT improved % yes no yes no no no yes no yes no yes no yes no yes no no no yes no 38 10

11 SCRR Mechanism & References Improvement effect of liquefiable soils 2nd in-situ test: by heavy dynamic penetrometer (DPH) DPH blows increased from 19 for intact soil to 33 at 10 m. The sand property increases from medium dense to dense, and very dense. The DPH test should have advanced further. 3-4 m surrounding liquefiable soil loses liquefaction properties. Figure 8. The DPH test outcomes before and after RBB compaction, Langfang, China (adapted from Luo 2010). 11

12 SCRR Mechanism & References Ishihara 1985 Crust Theory: Liquefaction Potential Mitigation Figure 9: Definition of surface un-liquefiable layer & underlying liquefiable sand layer (Ishihara 1985). Thin/weak stable layer on top. Liquefiable soil gets displaced modified, densified, & consolidated Liquefiable potential got bridged by the reliable SCRR CRUST. Figure 10: liquefaction potential removed 12

13 SCRR Mechanism & References 1st layer is the major structural layer, 2nd layer is the reinforced layer. Figure 11: work sample liquefaction potential removed. 13

14 Refusal Design Design & Quality Control Penetration test Pt, 4 T ram, 5 m free falling distance. Penetration Pt designed; capacity Ra designed, small & even settlement Vertical bearing strength per bulb, Ra: R a = f a A e (2) Table 2. Effective bearing area of SCRR bulb in sand (adapted from CMC 2007). Three drive penetration, cm Strengthened layer Medium dense 2.4~ ~ ~2.2 Fine sand Slightly dense 2.8~ ~ ~2.6 Medium to coarse sand f a = f ak + η d γ m (d - 0.5) (3) or f a = n x (in situ testing value, CPT, SPT) (4) Medium dense 2.7~ ~ ~2.4 Slightly dense 3.1~ ~ ~2.8 Verification of SCRR Quality SCRR raft: consistency & integrity validated by MASW (Park et al. 2007). Piles + SCRR option: traditional testings (Yang et al. 2010, Franki 2015, Puissant 2015). 14

15 SCRR Mechanism Sum-up partially similar to: 1. Surface Dynamic Compaction: surface scattered improvement 3. Franki Pile or Enlarged Base piling: piling 2. Stone Columns or Compacted Sand Pier: scattered improvement to a depth 5. Surface gravel raft: limited depth, excavation cost & risk, retaining, dewatering, stocking space, high cost, pipelines & planting issues. Figure 12: SCRR and Referenced Mechanism 4. Bearing base piling: pile with enlarged base 15

16 Advantages & Limitations Advantages Eliminating liquefaction damages: robust way to solve liquefaction problems Displacing, densifying, bridging and separating, Construction work realisable in Red Zone in Christchurch (Red zone TC2 & TC3, TC1). Permanent foundation: (timber, rebar, H column, screw) Environmental & ecological benefits: Each SCRR bulb uses m 3 of rubbles. SCRR sites are tidy without mud, dewatering and excavation. No reverse impact on plants & underground networks. Easy quality control: penetration test. Materials easy to source, low cost: construction or demolition wastes, concrete, stone. Economic benefits: comprehensive SCRR foundation saves 30-60% cost. Fast in construction: 1-2 m 2 per hour. Figure 13. SCRR under underground networ Government wastes minimisation policies: NZ (2002) & Australia (2011). Wide application: most engineering & geological conditions: problematic ground. Limitations Needs further detailed research and site experiments. 16

and/or weak soil layers. SCRR densifies weak layers Increase foundation bearing strength.

17 Implied Applications SCRR increases upper critical thickness. Road foundations; Underground services; Residential buildings on liquefiable soil sites and/or weak soil layers. SCRR densifies weak layers Increase foundation bearing strength. Decrease settlement & differential settlement. Figure 14. SCRR under a main road. Figure 15. SCRR under underground network. 17

Implied Applications Use of SCRR in addition to piles is an appropriate solution Multi-storey buildings or. Normal houses with heavy cladding and roofing materials.

18 Implied Applications Use of SCRR in addition to piles is an appropriate solution Multi-storey buildings or. Normal houses with heavy cladding and roofing materials. Such as those in Christchurch TC2 and TC3 zones. Where, SCRR eliminates liquefaction potential, Provides reliable bearing capacity. Figure 16. SCRR for multi-storey house with pile foundations. 18

19 1. Numerical modelling Research Proposal Dynamic installation simulations available for referenced techniques. Compacted gravel raft foundations (NZGS 2015) Raft Structure & functions. Surface dynamic compaction Huge Compaction energy. FRANKI piles (Franki Foundations Group 2015) large subsurface bases. Bearing Base piles (Mr Jizhong Wang 1998) Demolition rubbles use & bases. Stone Columns (Germany 1950s) Bottom compaction and bases. None involved in multi-cycle insertion & compaction at depth. Therefore, the SCRR dynamic numerical modelling work is challenging. 2. Lab tests and site experiments Heavy CPT: density, consistency & uniformity for quality assurance. CPT data are inputted into C-Liq to analyse liquefaction potential alterations. 19

20 Advantages & Applications Conclusion &Discussion Eliminate the liquefaction risk. Improves the bearing capacity of weak ground. Consumes quantities of demolition wastes. It is suitable for most engineering and geological conditions. Its quality control is easy to manage. Economical and environment-friendly technology. Further research to gain a wide acceptance, it requires: Further advanced and rigorous analysis. Numerical modelling studies. In-situ experiments. Significance Technical, economical and environmental benefits to the society. 20

Thank you! Questions? Reference Bo M. W., Na Y. M., Arulrajah A, & Chang M. F. 2009. Densification of granular soil by dynamic compaction, Proc. ICE - Gr. Improv., vol. 162, no. 3, pp. 121 132.

21 Thank you! Questions? Reference Bo M. W., Na Y. M., Arulrajah A, & Chang M. F Densification of granular soil by dynamic compaction, Proc. ICE - Gr. Improv., vol. 162, no. 3, pp Chinese Ministry of Construction Chinese Professional Standards: Design Specification of Ram-compacted Piles with Base Bearing (JGJ ), Construction Industry Publisher, Beijing, China, 2007 (in Mandarin). Department of Environment Australia Construction and demolition waste status report-management of construction and demolition waste in Australia, retrieved from on 20 Feb Franki Foundations Group FRANKI pile, retrieved from GeoLogismiki Software CLiq v.1.7 Soil liquefaction software, Ishihara K Stability of natural deposits during earthquakes, Proc., 11 th Int. Conf. on Soil Mechanics and Foundation Engineering., San Francisco, 1985, Leonards G. A., Cutter W. A. and Holtz R. D Dynamic compaction of granular soils. Journal of the Geotechnical Engineering Division, ASCE, 106, No. 1, Ministry for the Environment New Zealand The Guide to Managing Cleanfills: Acceptable cleanfill material, retrieved from NZGS Geotechnical earthquake engineering practice, MODULE 5A: Specification of ground improvement for residential properties in the Canterbury region, New Zealand Geotechnical Society (NZGS), Ver. 1, Park C.B., Miller R.D., Xia J.H & Ivanov J Multichannel analysis of surface waves (MASW). The Leading Edge, January 2007, /doi/abs/ / Puissant Group Ltd The profile of Puissant Group Ltd, Beijing, July 2015 (in Mandarin). Qi, Y.SH Application of Ram-compacted Pile with Base Bearing, National Seminar for Enforcing the New Chinese National Standards JGJ Beijing (in Mandarin). Robertson P. K & Cabal K.L. (Robertson) Guide to Cone Penetration Testing for Geotechnical Engineering, Gregg Drilling & Testing, Inc. 6th Edition, pp140. Retrieved from State Intellectual Property Office of the PRC Construction method for concrete pile, CN C, retrieved from on 20 Feb Tonkin & Taylor Ltd Liquefaction vulnerability study Report, Earthquake Commission New Zealand, Report, Tonkin & Taylor Ltd, T&T Ref /v1.0, pp59. Wang, J.Z Birth and development of the Ram-compacted Pile with Bearing Base, Building and Structure, Vol 38 (4), April 2008, Beijing, China (in Mandarin). Yang, J., Zhang, B.L., & Chong, Y Design Practice of the Ramp-compacted Pile with Bearing Base, Engineering of Coal Industry, 2010 (11) Yang, Q.A. & Wang, J.Z Expansive Research of the Ram-compacted Piles with Bearing Base, Eng. of Road and Foundations, Vol 156 (3), 68-71, 2011 China (in Mandarin). Yang, Q.A. & Wang, J.Z Effect of Ramp-compacted Pile with Bearing Base to Nearby Soils, J. of Foundation Technology Forum, 2012, China (in Mandarin). Youd, T.L. & Garris, C.T Liquefaction-induced ground surface disruption, J. Geotech. Eng. 121 (11), Zhu, X.F Application of Bearing Base Pile Composite Foundation in Liquefied Soil Treatment in a High Speed Railway Project, Guangdong Highway and Traffic, Issue 124, 2013, Guangdong, China (in Mandarin). 21

Evaluation the Effectiveness of Rapid Impact Compaction (RIC) as a Ground Improvement Technique

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