We Don t Need No Stinkin Anchors! Using the Box Reinforcing Effect for Self Supporting SOE ADSC West Coast Chapter Annual Meeting Spring 2018 Pismo Beach, CA Presented by Ben Turner, Ph.D., P.E. Dan Brown and Associates, California Treasure of the Sierra Madre (1948), Warner Bros. Project Overview High GWT SAND/ Mixed Alluvium + Boulders GLACIAL TILL Boulders CLAY Mixed soil profile with variable, uncertain depth to hydraulic barrier layers SHALE, LIMESTONE Annual Meeting Spring 2018 2 1
Project Overview How can we design and build a supportof excavation (SOE) system for a 35+ ft deep cut? Annual Meeting Spring 2018 3 Project Overview Limited ROW How can we design and build a supportof excavation (SOE) system for a 35 ft deep cut without anchors? Annual Meeting Spring 2018 4 2
Project Overview How can we design and build a supportof excavation (SOE) system for a 35 ft deep cut without anchors or internal bracing? Annual Meeting Spring 2018 5 East Side Pump Station SOE Project Team: SOE D B Team: Goettle Construction and DBA GC: Dugan & Meyers Owner: City of Miamisburg, Ohio Owner s Engineer: Hazen and Sawyer Annual Meeting Spring 2018 6 3
East Side Pump Station SOE DBA Team: Mark Madgett Tim Seigel Ben Turner Tayler Day Goettle Team: Brent Burman PM Chad Linz PM Wes Campbell Super. Annual Meeting Spring 2018 7 Location Annual Meeting Spring 2018 8 4
Initial Project Development Specs originally called for dewatering Difficult with high groundwater, variable ground conditions Concerns re/ mobilizing nearby contaminant plume Annual Meeting Spring 2018 9 Alternative Concept Cutoff wall around footprint of pump station to separate from surrounding aquifer, eliminating need for dewatering outside wall 694 684 660.5 Annual Meeting Spring 2018 10 5
Alternative Concept Cutoff wall around footprint of pump station to separate from surrounding aquifer, eliminating need for dewatering outside wall 694 684 660.5 Requires stiff wall? Uncertainty w.r.t. water cutoff Annual Meeting Spring 2018 11 Alternative Concept Requires stiff wall 694 684 Uncertainty w.r.t. water cutoff Boulders sheetpile 660.5 Alternatives: Secant pile wall (DBA/Goettle)? Diaphragm wall Annual Meeting Spring 2018 12 6
Preliminary Design 694 694 694 684 684 684 660.5 ~40 645.5 660.5 Stage 1: Excavate to elev. 660.5 If excavation remains dry, pour slab/walls done. Stage 2: If can t maintain dry excavation, flood, then excavate another 8 15 for seal slab Stage 3: Tremie pour seal slab; dewater when cured. Similar to Stage 1 (dry), but with slab in place is less critical. Annual Meeting Spring 2018 13 Preliminary Design 1500 mm diam. secant piles 18 No. 11 bars, or Wide flange section 55 65 ft piles desirable Longer would require significant drilling through till w/ large boulders; uncertain depth to rock Annual Meeting Spring 2018 14 7
Preliminary Design Stage 2 unstable even with W44x335 Annual Meeting Spring 2018 15 Preliminary Design Based on 2 D (plane strain) methods, cantilever wall does not work even with large diam., heavily reinforced secant piles. Annual Meeting Spring 2018 16 8
Preliminary Design Based on 2 D (plane strain) methods, cantilever wall does not work even with large diam., heavily reinforced secant piles. But, this is not a 2 D problem! Annual Meeting Spring 2018 17 3 D Effects in Excavations lateral earth/water pressure deflected shape PLAN Long excavation sides are not influenced by adjoining wall segments Plane strain, 2 D analysis is appropriate ELEVATION Annual Meeting Spring 2018 18 9
3 D Effects in Excavations PLAN In circular excavations, lateral loads (radial stress) are converted to in plane loads (hoop stress) through arch effect E. Lindquist and R. Jameson. (2011). Secant Pile Shoring Developments in Design and Construction. Proc. DFI Annual Conf. 8 p. 3 D Effects in Excavations lateral earth/water pressure? deflected shape PLAN Short sides are restrained by adjoining segments Analogous to simply supported beam ELEVATION Annual Meeting Spring 2018 20 10
3 D Effects in Excavations Despite simple conceptual basis, support of adjoining wall segments not typically accounted for in design of rectangular excavations lateral earth/water pressure deflected shape PLAN Annual Meeting Spring 2018 21 3 D Effects in Excavations Despite simple conceptual basis, support of adjoining wall segments not typically accounted for in design of rectangular excavations Why? Lack of awareness, or perceived as poorly understood mechanism Commonly used analysis tools (e.g., PYWALL, LPILE) are poorly suited to capturing this effect lateral earth/water pressure deflected shape PLAN Annual Meeting Spring 2018 22 11
Finno et al. (2007) 3D 2D Finno, RJ, Blackburn, JT, and Roboski, JF (2007). 3 D Effects for Supported Excavation in Clay. JGGE, 133(1). Annual Meeting Spring 2018 23 Proposal Developed on the basis of box reinforcing effect Match contractor s tooling and strengths 1500 mm diam. secant piles Construction considerations Corner radius for guide wall construction Reinf. beams versus cages limited stockpile space, more overlap Annual Meeting Spring 2018 24 12
Design Phase More robust analysis method required to support 3 D box effect Provides means for estimating behavior and order of magnitude of deformation and stresses Provides point of reference for monitoring during construct. A tool, not a design method! Annual Meeting Spring 2018 25 Modeling Annual Meeting Spring 2018 26 13
Modeling Annual Meeting Spring 2018 27 Modeling Allow interface slip Annual Meeting Spring 2018 28 14
Modeling Reduced order model allows parametric analysis Vary stratigraphy and soil props Evaluate different pile lengths and reinf. Annual Meeting Spring 2018 29 Results 55 ft, 1500 mm diam. piles w/ W36x135 Max. conc. Stress 600 psi; min. 200 psi Max. inward deflect. 0.2 in. Informed monitoring plan (flag @ ¼ in.) Insights into box effect behavior Deformation patterns Stress concentrations corners and inside of piles Annual Meeting Spring 2018 30 15
Results Design sufficient to excavate extra 12 ft for seal slab if needed Allows computation of basal heave FoS index (also a 3D mechanism) Model allows evaluating effects of significant water infiltration or flooding to control basal heave Annual Meeting Spring 2018 31 Results Model allows evaluating effects of significant water infiltration But not a means for determining if it will happen in the first place! Depends on ground + hydraulic conditions (uncertain) Annual Meeting Spring 2018 32 16
Construction Guide wall template: Alignment Primary/secondary overlap Corners Annual Meeting Spring 2018 33 Construction: Corners Original Design Annual Meeting Spring 2018 34 17
Construction: Corners Potential kickout during drilling Original Design Annual Meeting Spring 2018 35 Construction: Corners Potential kickout during drilling Original Design Constructed Annual Meeting Spring 2018 36 18
Construction A572 GR50 W36x135 Annual Meeting Spring 2018 37 Construction Pour + drill same time Primary piles f c =2 ksi Secondary piles f c = 4 ksi 7 10 in. slump specified 9 in target Annual Meeting Spring 2018 38 19
Excavation Annual Meeting Spring 2018 39 Excavation Annual Meeting Spring 2018 40 20
Excavation Dry! Annual Meeting Spring 2018 41 Pump Station Floor Annual Meeting Spring 2018 42 21
Monitoring Prediction 0.07 0.09 Measured Annual Meeting Spring 2018 43 Monitoring Prediction range 0.05 0.22 Measured range 0.07 0.1 System is very stiff good! Gives confidence that predictions of max. stress used in design are within range Annual Meeting Spring 2018 44 22
Success! 45 Not so fast https://www.wunderground.com/cat6/biggest-flood-20-years-hits-ohio-river Annual Meeting Spring 2018 46 23
Just when you think it s over Annual Meeting Spring 2018 47 Just when you think it s over Annual Meeting Spring 2018 48 24
Just when you think it s over Annual Meeting Spring 2018 49 Just when you think it s over Analysis results gave confidence could dewater safely Annual Meeting Spring 2018 50 25
Final Disp. after Pumping Dry Annual Meeting Spring 2018 51 Summary Well built finished product Guide template High slump concrete Segmental casing With box effect, W36x135 worked compared to 2 D analysis (PYWALL) which predicted that W44x335 was insufficient Many applications where ROW or internal bracing undesirable Annual Meeting Spring 2018 52 26
Summary Numerical modeling should not drive a project; nature of project should dictate the appropriate analysis tool The best analysis tool is as simple as possible, but no simpler. ( Albert Einstein) Sometimes the software you have the license for is not the best tool for the job! Nonetheless, every program has weaknesses. Especially 3 D finite element/difference software. Annual Meeting Spring 2018 53 Summary When used appropriately, modeling can provide a good link between simpler analysis methods, expected behavior, and monitoring during construction Handled unforeseen flooding with confidence thanks to analysis Good agreement between model and observed behavior sleep better Annual Meeting Spring 2018 54 27
Thanks Annual Meeting Spring 2018 55 28