Mueser Rutledge Consulting Engineers

Transcription

1 Mueser Rutledge Consulting Engineers - Geotechnical and Structural Foundation Engineering - Founded in New York City / Washington, DC - Practice areas Geotechnical Engineering Structural Design of Foundations Waterfront Structures

2 Managing Risk in Foundation Construction Srinivas Yenamandra, PE Structural Engineer Peter Deming, PE Geotechnical Engineer 2

3 3 About Our Firm

4 Commercial Development Four Seasons Hotel & Tower Baltimore, MD 4

5 Transportation The New NY Bridge Westchester County, NY 5

6 Education Columbia University s Manhattanville Campus, New York, NY 6

7 Healthcare SUNY Buffalo School of Medicine and Biomedical Sciences Buffalo, NY 7

8 Emergency Engineering NJ Transit Hoboken Terminal Train Crash, Hoboken, NJ 8

9 Forensic Engineering 9

10 Forensic Engineering Source: 10

11 Corvette Museum Engineering Goal cost efficient & quality construction Source: The National Corvette Museum Bowling Green, Kentucky 11

12 Corvette Museum Source: Source: 12

13 Corvette Museum Source: 13

14 Corvette Museum Storm water from dome infiltrated to ground, washing soil into void in rock. Loss of soil undermined slab, causing sudden collapse. Source: 14

15 Big Picture Risks Goal cost efficient construction Squeeze the design budget We don t have money until the construction loan comes in! Save time and money on field investigations figure it out later! 15

16 Big Picture Risks Ground movement = damage to adjacent properties / $$$ Differing Site Conditions = Construction delays and cost increase 16

17 Big Picture Risks Poor foundation performance: During construction = schedule bust & cost increase Completed structure = dissatisfied Owner / maintenance 17

18 Big Picture Risks Planning Pays off! Source: 18

19 Risk Areas Geotechnical Risks Soil Profile Non-uniform Difficult to define Poorly defined Soil Strength Not properly defined Non-uniform Influenced by groundwater Design error or omission Construction out of sequence Groundwater management Uncertainty introduces risk Swelling or softening of stiff clay 19

20 Risk Areas The Soil as Structural Component Soil profile and soil strength Used in design of temporary excavation support Used in design of permanent foundations Interpreted by the geotechnical engineer from facts (borings and test data). Source: 20

21 Risk Management in Design Boring spacing and depth Uniform soil conditions 300 ft spacing Non-uniform conditions 100 ft max spacing Split spacing in areas of change At least half # borings should extend below maximum depth of structure 21

22 Strength definition Soil load-history / Geology / Man-made influences Test strength and consolidation Confirm normal soil standard performance rule of thumb Risk Management in Design 22

23 Geotechnical Data Report Boring locations Soil Profile Test Data - Where What How Risk Management in Design Geotechnical Interpretation and Design Report Geologic setting and geotechnical history Interpret design parameters from Data Report testing Describe structure Define how structure obtains support Explain groundwater management in construction and permanent condition Provide calculations demonstrating safety factor / Code compliance Peer Review 23

24 Peer Review = Standard of Care and Code compliance Peer Review Third party review of planned work Subsurface conditions, design logic, and construction sequence Parameter assumptions, analysis methods, and analysis findings Factor of safety. NOT a computational check. Risk Management In Design Peer review deliverable - report and clarification conference Owner and designer determine what / how / if to address Peer reviewer liability limitations Source: 24

25 Risk Management In Design Peer Review is not Value Engineering Value Engineering = build a better mousetrap Alternative construction method for cost or schedule savings Performance of new design becomes responsibility of value engineer Source: 25

26 Risk Management In Construction Contract Drawings Define location of structure(s) Define required construction Describe instruments and criteria for construction monitoring Define construction sequence - coordinate with design expectation Drawing content is baseline for extra work 26 Source:

27 Risk Management In Construction Contract Specifications Set performance criteria often established by Code or estimated by calculation: Acceptable movement of adjacent structures Load test performance Identify Contractor obligations Outline Contractor submittals and approval authority Contract Specifications Include Add/Deduct Price provisions to manage unknowns (say rock excavation quantity) 27

28 Risk Management In Construction Contract Document Tips Beware of Means and Methods Specifications Don t specify HOW! End Product specifications are preferred Beware of conflict in contract documents Say it ONCE! Consistent use of common terms link work requirements: plan layout / details / specification criteria / Bid Form Set clear expectations for special inspections (paid by Owner or Contractor?) 28

29 Excavation Risks DEPTH (FT) FILL SOFT CLAY SAND COMPACT SAND Internal Brace Earth & Water Pressure Sheet Pile Hydraulic Cutoff at Glacial Till Excavation Support Design to support earth pressure and water pressure Earth pressure includes adjacent structure Design criteria = restrict deflection GLACIAL TILL BEDROCK 29

30 Excavation Risks DEPTH (FT) FILL SOFT CLAY SAND Depressed Water Table Lateral Load from Earth & Water Pressure Excavation Support Depress water table ahead of excavation Place braces as excavation progresses COMPACT SAND GLACIAL TILL BEDROCK 30

31 DEPTH (FT) FILL SOFT CLAY SAND COMPACT SAND Monitor Drawdown Mud Mat Excavation Risks Excavation Support Confirm water level below final subgrade Inspect final subgrade to confirm undisturbed and prove bearing capacity Protect final subgrade against disturbance (mud mat) GLACIAL TILL BEDROCK 31

32 DEPTH (FT) FILL SOFT CLAY SAND COMPACT SAND Mat Foundation Excavation Risks Excavation Support Maintain water level below final subgrade Place waterproofing, basement walls, and columns Place permanent floors and remove braces, in sequence GLACIAL TILL BEDROCK 32

33 Excavation Risks DEPTH (FT) FILL SOFT CLAY SAND COMPACT SAND Permanent Water Pressure Excavation Support Water level rebound after structure weight is sufficient Grout seal groundwater wells closed Lateral earth and water load permanently transferred to structure. Build out Sequence GLACIAL TILL BEDROCK 33

34 Excavation Risks Excavation Risks Adjacent Structures Construction Dewatering Foundation Construction / Subgrade Protection Permanent Waterproofing Build out sequence 34

35 Risk Management In Construction Strong Construction Management Engage design engineer for construction support and special inspections Establish clear lines of communications and responsibilities Maintain / respect project roles Timely RFI response Regular meetings / documented 35

36 Risk Management In Construction Instrumentation and Monitoring Allows Management Control to Reduce Risk: Pre-construction condition assessment Observe displacement of shoring or adjacent structures to evaluate performance. Technology allows remote precision survey and plotting almost real time. Monitor displacement trends Revise construction methods to reduce movement Monitor performance to confirm improvement Post-construction condition inspection 36

37 Risk in Foundation Construction Summary: How to reduce risk Up-front geotechnical information. Understand geotechnical design logic and construction sequence objectives. Design Report. Prepare quality Drawings and Specifications. Peer Review. Engage design engineer for construction support and special inspections. Communicate throughout the construction process. Monitor performance. Source: /how-to-be-successful/ 37

38 Srinivas Yenamandra, PE Peter Deming, PE Mueser Rutledge Consulting Engineers 14 Penn Plaza 225 West 34 th Street New York, NY USA Tel: Fax: