POTENTIAL STABILITY ISSUES THAT COULD AFFECT PERFORMANCE OF BRIDGE - - PowerPoint PPT Presentation

▶
potential stability issues that could affect performance
SMART_READER_LITE
LIVE PREVIEW

POTENTIAL STABILITY ISSUES THAT COULD AFFECT PERFORMANCE OF BRIDGE - - PowerPoint PPT Presentation

Oct 22, 2023 261 likes •998 views

POTENTIAL STABILITY ISSUES THAT COULD AFFECT PERFORMANCE OF BRIDGE FOUNDATION UNITS Short Term: Bearing Failure due to Imposed Loading Long Term: Ground Loss into Shafts or Mine Voids erosion of shaft plugs dissolution of

slide-1
SLIDE 1

1

POTENTIAL STABILITY ISSUES THAT COULD AFFECT PERFORMANCE OF BRIDGE FOUNDATION UNITS Short Term: Bearing Failure due to Imposed Loading Long Term:

  • Ground Loss into Shafts or Mine Voids
  • erosion of shaft plugs
  • dissolution of limestone
  • roof cave
  • Increased Loading Related to Regional Groundwater

Lowering

slide-2
SLIDE 2

2

Potential Mine Shaft Locations

slide-3
SLIDE 3

3

LONG TERM STABILITY ISSUE RELATED TO SHAFT CLOSURES

H Re Q Strong, competent Weak, non-bearing h

slide-4
SLIDE 4

4

PUNCHING FAILURE COMPOSITE BEAM BENDING

SHORT TERM STABILITY – BEARING FAILURE MECHANISMS

slide-5
SLIDE 5

5

PUNCHING FAILURE ANALYSIS

H Be Q Weak, compressible Strong, competent Weak, non-bearing h Punching Failure: FS = Resisting Force / Driving Force = π BeH (c + σN(tanΦ)) Q + Wo +Wr Where: c = cohesion σN = normal stress Φ = friction angle Wo = weight overburden Wr = weight rock

slide-6
SLIDE 6

6

FINITE ELEMENT ANALYSES Performed by Wyllie & Norrish Rock Engineers

  • 1. Used Phase2 Ver 5.048 software from Rocscience Inc.

to perform sensitivity analysis.

  • 2. For the model replaced twin bearing pads with a

single circular footing with radius of 4.8m and with same total load and bearing pressure.

  • 3. Footing simplification to enable axisymmetric model –

3D model that is rotationally symmetric about the line

  • f loading.
  • 4. Groundwater assumed to be at top-of-rock.

Incorporated by using buoyant unit weight for the rock mass.

slide-7
SLIDE 7

7

Finite Element Analyses – Roof Stability over Void

“Stable” “Marginal”

FAIR QUALITY 10 m beam depth 20 m void width Self weight FAIR QUALITY 10 m beam depth 40 m void width Self weight

slide-8
SLIDE 8

8

Finite Element Analyses – Roof Stability over Void with Foundation Load

“Stable” “Marginal”

FAIR QUALITY 10 m beam depth 20 m void width Foundation Load FAIR QUALITY 10 m beam depth 40 m void width Foundation Load

slide-9
SLIDE 9

9

Finite Element Analyses – Roof Stability over Void with Foundation and Embankment Load “Unstable” “Marginal”

GOOD QUALITY 5 m beam depth 60 m void width Foundation & Embankment Load GOOD QUALITY 10 m beam depth 60 m void width Foundation & Embankment Load

slide-10
SLIDE 10

10

ROCK BEAM – VOID DIMENSION SENSITIVITY BASED ON FINITE ELEMENT ANALYSES

Key:

Unstable Marginal Stable

Beam

Rock Foundation Embankment Foundation Embankment Foundation Embankment

Thickness

Quality Load & Foundation Load & Foundation Load & Foundation Only Load @ 10m Load @ 10m Load @ 10m

(m)

(0.5 MPa) (0.696 MPa) (0.5 MPa) (0.696 MPa) (0.5 MPa) (0.696 MPa) Poor

5

Fair Good Poor

10

Fair Good Poor

20

Fair Good Poor

40

Fair Good Self Weight Self Weight Self Weight

Void Width (20m) Void Width (40m) Void Width (60m)

slide-11
SLIDE 11

11

CLOSED FORM PLATE BENDING ANALYSIS (after Wyllie, 1999)

H Be Q VOID Strong, competent Overburden / Embankment rv Bending Failure: FS = Resisting Rockmass Tensile Strength / Induced Tensile Stress (σt) Where: σt = 6M/H2 M = (Q + Wo + Wr/2) [(1+ν)loge(r/r0)+1], B>H, then ro = B/2 4π B<H, then ro = [1.6(B/2)2+H2]0.5 – 0.67H ν = Poisson’s ratio, rv = radius of void, Wo = weight of overburden, Wr = weight rock

slide-12
SLIDE 12

12

Comparison of Analytical Approaches

Unstable

FS<1.0

Marginal

FS<2.5

Stable

FS>2.5

Beam

Rock Foundation Embankment Foundation Embankment Foundation Embankment

Thickness

Quality Load & Foundation Load & Foundation Load & Foundation Only Load @ 10m Load @ 10m Load @ 10m

(m)

(0.5 MPa) (0.696 MPa) (0.5 MPa) (0.696 MPa) (0.5 MPa) (0.696 MPa) Poor 0.03 0.02 0.02 0.01 0.02 0.01

5

Fair 0.28 0.21 0.22 0.16 0.19 0.14 Good 1.53 1.12 1.16 0.85 1.02 0.74 Poor 0.12 0.09 0.08 0.06 0.07 0.05

10

Fair 1.29 0.96 0.93 0.69 0.8 0.6 Good >5 >5 5 3.73 4.3 3.21 Poor 0.61 0.47 0.39 0.3 0.32 0.24

20

Fair >5 >5 4.27 3.29 3.52 2.71 Good >5 >5 >5 >5 >5 >5 Poor 4.39 3.55 1.9 0.77 1.43 1.15

40

Fair >5 >5 >5 >5 >5 >5 Good >5 >5 >5 >5 >5 >5

Void Width (20m) Void Width (40m) Void Width (60m)

Self Weight Self Weight Self Weight

Unstable Marginal Stable

Beam

Rock Foundation Embankment Foundation Embankment Foundation Embankment

Thickness

Quality Load & Foundation Load & Foundation Load & Foundation Only Load @ 10m Load @ 10m Load @ 10m

(m)

(0.5 MPa) (0.696 MPa) (0.5 MPa) (0.696 MPa) (0.5 MPa) (0.696 MPa) Poor

5

Fair Good Poor

10

Fair Good Poor

20

Fair Good Poor

40

Fair Good Self Weight Self Weight Self Weight

Void Width (20m) Void Width (40m) Void Width (60m)

Closed Form Plate Bending Analysis Phase2 Finite Element Analysis

slide-13
SLIDE 13

13

CONFIRMED VOID ANALYSIS

Deep Good 47.0 B1 6 6149 Deep Good 45.5 A 1 6148 Deep Fair/Good 44.5 B2 3 6140 Deep Fair 42.5 B2 1 6149 Chaotic Good 22.6 B2 7 6149 Chaotic Poor 20.0 B2 2 6140 Chaotic Good 5.1 B2 8 6149 Chaotic Fair 1.5 B2 3 6150 Chaotic Fair 0.9 B2 1 6140 Mine Horizon Rock Quality Beam Thick (m) Foundation Type (prelim) Bent Bridge

slide-14
SLIDE 14

14

CONCLUSIONS – APPLICATION TO FOUNDATION DESIGN 1. Deep mine workings with “fair” or “good” rock quality should not represent a stability issue. 2. Deep mine workings with extreme lateral continuity and “poor” quality rock cover will require grout improvement (e.g. bridge A6149 – A6140 confluence). 3. Upper chaotic mine workings will require site specific probe and treatment approach during construction. Targets elevations for treatment can be provided in advance. 4. A number of locations will be suitable for spread footings subject to ground verification during construction.

slide-15
SLIDE 15

15

Presentation of Ground Conditions for Foundation Design Micropile Footing Spread Footing

slide-16
SLIDE 16

16

Foundations for Bents – Exploration and Pretreatment

Anticipated Grout Type Use Versus Ground Classification and Intensity of Treatment.

HMG 100% HMG 40% HMG 30% LMG 60% LMG 70%

Low Intensity Medium Inte nsity High Intensity Type 1 Type 2 Type 2

Relati ve Consumption Anticipated

  • f ea

ch Grout Type Treatment Intensity Ground Classification

slide-17
SLIDE 17

17

Anticipated Footing Types and Pretreatment Method

Low Intensity (7): A6140 - EB3 Treatment – Spread Ftgs A6148 – EB1, B2, B3, EB4 A6149 – EB9 A6150 – EB1 Medium Intensity (6): A6149 – B3, B6 Treatment – Micropile Ftgs A6150 – B2 A6165 – EB1, B2, EB3 High Intensity (10): A6140 – EB1, B2 Treatment – Micropile Ftgs A6149 – EB1, B2, B4, B5, B7, B8 A6250 – B3, EB4

slide-18
SLIDE 18

18 MSE Wall A7263 MSE Wall A7264 MSE Wall A7265

  • Br. A6149
  • Br. A6150
  • Br. A6148
  • Br. A6140
  • Br. A7262
  • Br. A7261
  • Br. A7260
  • Br. A6165

Structure Site Plan – 3 MSE Walls, 3 Box Culverts, and 5 Bridges

slide-19
SLIDE 19

19

MSE Wall A7263

MSE Wall Plan Layout

slide-20
SLIDE 20

20

MSE Wall Typical Section at Bridge End Bent

slide-21
SLIDE 21

21

  • Philosophy

– Locate and treat unforeseen mine features and/or voids prior to wall construction

  • Construction Procedure

– Drill primary holes (30-meters ea.) under the front face of wall – Drill primary holes (20-meters ea.) in predetermined pattern under the footprint of the wall reinforced mass – Grout primary holes utilizing Low Mobility Grout (LMG)

  • Small fissure grouting is not necessary

Ground Pretreatment at MSE Walls

slide-22
SLIDE 22

22

Typical Pretreatment Pattern at MSE Wall

slide-23
SLIDE 23

23

Ground Pretreatment at Bridge Embankments

  • Philosophy

– Locate and treat unforeseen mine features and/or voids below embankments around bridge foundations

  • Construction Procedure

– Drill primary holes (30-meters ea.) in predetermined pattern shown on drawings – Grout primary holes utilizing Low Mobility Grout (LMG)

  • Small fissure grouting is not necessary
slide-24
SLIDE 24

24

Typical Pretreatment Pattern at Bridge Embankments

slide-25
SLIDE 25

25

  • Philosophy:

– Locate and treat unforeseen mine features and/or voids below box culvert bottom slab

  • Construction Procedure

– Drill primary holes (20-meters ea.) in predetermined pattern within the footprint of each box culvert – Grout primary holes utilizing Low Mobility Grout (LMG)

  • Small fissure grouting is not necessary

Ground Pretreatment at Box Culverts

slide-26
SLIDE 26

26

Typical Pretreatment Pattern at Box Culverts

slide-27
SLIDE 27

27

Bridge A6140

Bridge Layout Showing Foundations

slide-28
SLIDE 28

28

Bridge A6148

Bridge Layout Showing Foundations

slide-29
SLIDE 29

29

Bridge A6149

Bridge Layout Showing Foundations

slide-30
SLIDE 30

30

Bridge A6149

Bridge Layout Showing Foundations

slide-31
SLIDE 31

31

Bridge A6150

Bridge Layout Showing Foundations

slide-32
SLIDE 32

32

Bridge A6165

Bridge Layout Showing Foundations

slide-33
SLIDE 33

33

  • Philosophy:

– Locate and treat unforeseen mine features and/or voids at bridge footings – Verify the nature of the rock mass under each footing – Treat the ground:

  • To improve mechanical properties of the rock mass
  • Limit subsequent micropile grout takes
  • “Intensity” of Ground Pretreatment

– Low Intensity – “Type 1” Ground Conditions – Medium Intensity – “Type 2” Ground Conditions – High Intensity – “Type 2” Ground Conditions

Ground Pretreatment at Bridge Foundations

slide-34
SLIDE 34

34

  • Low Intensity Ground Pretreatment

– Drill and grout primary and secondary holes (Low & High Mobility Grout) – Real time monitoring, processing and interpreting the drilling and grouting data is critical in determining need and location for additional treatment holes

Ground Pretreatment at Bridge Foundations

slide-35
SLIDE 35

35

Low Intensity Ground Pretreatment at Bridge Foundations

Spread Footings on Sound Limestone Type 1 Ground Conditions

slide-36
SLIDE 36

36

  • Medium Intensity Ground Pretreatment

– Drill and grout primary, secondary and tertiary holes (Low & High Mobility Grout) – Real time monitoring, processing and interpreting the drilling and grouting data is critical in determining need and location for additional treatment holes

Ground Pretreatment at Bridge Foundations

slide-37
SLIDE 37

37

Medium Intensity Ground Pretreatment at Bridge Foundations

Micropile Footing Type 2 Ground Conditions

slide-38
SLIDE 38

38

  • High Intensity Pretreatment

– Drill and grout primary, secondary, tertiary and quaternary holes (Low & High Mobility Grout) – Real time monitoring, processing and interpreting the drilling and grouting data is critical in determining need and location for additional treatment holes

Ground Pretreatment at Bridge Foundations

slide-39
SLIDE 39

39

High Intensity Ground Pretreatment at Bridge Foundations

Micropile Footing Type 2 Ground Conditions

slide-40
SLIDE 40

40

Ground Pretreatment at Bridge Foundations Typical Plan Sheet

slide-41
SLIDE 41

41

Spread Footing Construction – Typical Plan Sheet

slide-42
SLIDE 42

42

Micropile Footing Construction – Typical Plan Sheet

slide-43
SLIDE 43

43

Micropile Details in Plans

slide-44
SLIDE 44

44

Micropile Elevation View in Plans

slide-45
SLIDE 45

45

Micropile Section Views in Plans

slide-46
SLIDE 46

46

Micropile Design Summary in Plans

Total Number of Micropiles – Design Compression Load – 827 to 1891 kN Design Tension Load – 0 to 925 kN

slide-47
SLIDE 47

47 Good to Fair Quality Limestone 3 2 0.51 6 287 293 1439 8 Good Quality Limestone 3 2 0.53 6 288 294 1510 7 Good to Excellent Quality Limestone, Occasional Poorer Quality due to Thin Bedding

  • r Brecciation

3 2 0.55 6 288 294 1565 6 Weak, Weathered Limestone and Confused Ground 1,2 2 0.31 10 281 291 1480 5 Poor to Fair Quality Limestone 3 2 0.45 6 284 290 1271 4 Good to Excellent Quality Limestone, Occasional Poorer Quality due to Thin Bedding

  • r Brecciation

3 2 0.55 6 287.5 293.5 1556 3 Good to Excellent Quality Limestone, Occasional Poorer Quality due to Thin Bedding

  • r Brecciation

3 2 0.58 6 284.3 290.3 1649 2 Weak, Weathered Limestone, Shale, and Sandstone for top 6m, Improving Rock Quality Below 1,2 2 0.31 10 281 291 1437 EB-1 6149 Broken, Confused and Chaotic Limestone/Chert 1,2 2 0.26 15.5 275.5 291 1891 2 Weak, Weathered Limestone for top 3m, Improving Rock Quality Below with Voids Encountered 1,2 2 0.38 8 285 293 1423 EB-1 6140 End Begin Length (M) Elevation Geologic Description from Baseline Ground Conditions Verification Test Pile Number Ground Type Average Working Bond Stress (Mpa) Bond Zone Compressive Load (kN) Bent No Bridge No As-Designed Micropile Conditions

As-Designed Micropile Conditions

slide-48
SLIDE 48

48 Weak Shale, Highly to Moderately Disturbed, Minor Limestone 4 2 0.33 12 280 292 1846 EB-3 Weak Shale, Highly to Moderately Disturbed, Minor Sandstone 4 2 0.18 12 278 290 1035 2 Weak Shale, Highly to Moderately Disturbed, Minor Sandstone and Limestone 4 2 0.33 12 279 291 1846 EB-1 6165 Weathered Limestone and Lesser Amounts of Coal/Shale for top 6m, Rock Quality Below is Poor 1,2 2 0.38 10 279 289 1784 EB-4 Weathered Limestone and Coal/Shale for top 2m, Improving Rock Quality Below 1,2 2 0.29 6 279 285 827 3 Moderately Weathered Limestone and Shale, Good Rock Quality 1,2 2 0.35 5 284 289 827 2 6150 End Begin Length (M) Elevation Geologic Description from Baseline Ground Conditions Verification Test Pile Number Ground Type Average Working Bond Stress (Mpa) Bond Zone Compressive Load (kN) Bent No Bridge No As-Designed Micropile Conditions (Continued)

As-Designed Micropile Conditions (Con’t)

slide-49
SLIDE 49

49

Verification Test Program in Plans

slide-50
SLIDE 50

50

42 m3 LMG = volume and type of grout injected

= order installed

(Specific for Test Pile 2) 120º 1 2 º North

  • A

B C D 60º

  • 42 m3 LMG

12.3 m3 LMG 2.2 m3 LMG VP2 2 m 6.3 m3 HMG

Layout of Pretreatment Holes for Verification Test Pile 2

slide-51
SLIDE 51

51

  • Pre-production “sacrificial” piles with unbonded

length in overburden and bonded length in rock.

  • Maximum tension test load not to exceed 80% of

reinforcement structural capacity

  • Verify ultimate grout/ground bond values in different

ground types anticipated over the site

  • Verify creep performance at various load increments

and at maximum test load (10 and 60 minutes)

  • Verify a measured Factor of Safety (e.g., 2.0 to 3.0)

Verification Test Pile Program

slide-52
SLIDE 52

52

Verification Tests - Planned Program

Not Pretreated Not Pretreated Pretreated Not Pretreated Ground Pretreatment Constants:

  • 1. Hole Diameter: 152mm
  • 2. Rebar: 63.5mm, Grade 1034

Shale Good Limestone Poor & Confused Limestone Poor & Confused Limestone Bond Zone Material 3 m 3 m 4 m 4 m Bond Length VP4 VP3 VP2 VP1 Test Number

slide-53
SLIDE 53

53

Location of Verification Test Piles

slide-54
SLIDE 54

54

Note: Difference in ground for VP1, VP2 and VP3 Not Pretreated Not Pretreated Pretreated Not Pretreated Ground Pretreatment Shale Poor Quality Limestone (Good Limestone) Confused Shale and Clay (Poor & Confused Limestone) Sound Limestone (Poor & Confused Limestone) Bond Zone Material 3m 3.1m 4m 4m Bond Length VP4 VP3 VP2 VP1 Test Number

As Installed Program

As-Installed Verification Tests

slide-55
SLIDE 55

55

0.18 – 0.33 MPa 0.45 – 0.58 MPa 0.26 – 0.38 MPa 0.26 – 0.38 MPa Design Bond Values 1.46 MPa (F) 1.54 MPa 1.15 MPa (F) 1.16 MPa Average Bond at Maximum Load NA 0.057 mm 2.248 mm 0.248 mm Creep (1-10 min.) at Maximum Load 7.4 mm (F) 2.6 mm 12.9 mm (F) 2.8 mm Permanent Movement at Maximum Load Shale Poor quality Limestone Pregrouted confused shales and clay Sound Limestone Actual Geologic Conditions 2088 kN (Failure) 2210 kN 2210 kN (Failure) 2210 kN Maximum Load Sustained VP4 VP3 VP2 VP1 Test Number

Verification Test Summary of Results

slide-56
SLIDE 56

56

Verification Pile 1 (VP-1)

Pile (VP1) Top Displacement

10 100 1000 10000 5 10 15 20 25 30 35 40 Displacement, mm Load, kN 0.5DL 0.75DL 1.0DL 1.25DL 1.5DL 1.75DL 2.0DL

Pile (VP1) Top E lastic/Permanent Displacement

500 1000 1500 2000 2500 5 10 15 20 25 30 35 40

Displacement, mm Load, kN

Elastic Permanent Total

slide-57
SLIDE 57

57

Verification Pile 2 (VP-2)

Pile (VP2) Top Displacement

10 100 1000 10000 10 20 30 40 50 60 Displacement, mm Load, kN 0.5DL 0.75DL 1.0DL 1.25DL 1.5DL 1.75DL 2.0DL

Pile (VP2) Top E lastic/Permanent Displacement

500 1000 1500 2000 2500 5 10 15 20 25 30 35 40 45 50

Displacement, mm Load, kN

Elastic Permanent Total

slide-58
SLIDE 58

58

Verification Pile 3 (VP-3)

Pile (VP3) Top Displacement

10 100 1000 10000 5 10 15 20 25 30 35 40 Displacement, mm Load, kN 0.5DL 0.75DL 1.0DL 1.25DL 1.5DL 1.75DL 2.0DL

Pile (VP3) Top E lastic/Permanent Displacement

500 1000 1500 2000 2500 5 10 15 20 25 30 35 40

Displacement, mm Load, kN

Elastic Permanent Total

slide-59
SLIDE 59

59

Verification Pile 4 (VP-4)

Pile (VP4) Top Displacement

10 100 1000 10000 10 20 30 40 50 Displacement, mm Load, kN 0.5DL 0.75DL 1.0DL 1.25DL 1.5DL 1.75DL

Pile (VP4) Top E lastic/Permanent Displacement

500 1000 1500 2000 2500 5 10 15 20 25 30 35 40 45

Displacement, mm Load, kN

Elastic Permanent Total

slide-60
SLIDE 60

60

Verification Tests Conclusions

  • Tests were generally well conducted and produced

reliable data

  • VP1 and VP3 were tested to maximum test load

without failure

  • VP2 and VP4 failed at or slightly below the maximum

test load

  • Range of tested maximum bond values was 1.15 to

1.54 MPa

slide-61
SLIDE 61

61

Verification Test Conclusions (con’t)

  • FOS > 3 in all tests relative to design values
  • Design assumptions were verified as being

appropriate

  • Actual ground conditions may vary from what

was anticipated from design assumptions

  • Need for close monitoring of ground

pretreatment drilling and grouting as well as micropile drilling to confirm or modify unbonded and bonded lengths

slide-62
SLIDE 62

62

Micropile Reinforcement Assembly

slide-63
SLIDE 63

63

Micropile Reinforcement Installation

slide-64
SLIDE 64

64

Verification Load Test Setup

slide-65
SLIDE 65

65

Reference Beam and Dial Gauges

slide-66
SLIDE 66

66

Performing Load Test

slide-67
SLIDE 67

67

Recording Load Test Readings

slide-68
SLIDE 68

68

Jack and Load Cell

slide-69
SLIDE 69

69

Construction Monitoring - QA/QC

Contract included the monitoring, recording and analysis of construction data generated in real time

  • Ground pretreatment drilling and grouting data
  • Micropile drilling and grouting data

Analysis of these data is particularly important on this project in real time to assure that a responsive treatment is provided at each location and micropile lengths are acceptable The successful implementation of this concept required: (i) The engineering and technical cooperation of the Specialty Contractor (ii) The full-time on-site monitoring, recording, evaluation and decision making by the Design Team’s representative with the support of the other Design Team members.

slide-70
SLIDE 70

70

Outline of Geotechnical Baseline Report (GBR)

VOLUME I

  • Introduction
  • Site Geology
  • Mining and History of Site
  • Geotechnical Investigations
  • Groundwater Information
  • Laboratory Testing
  • Subsurface Conditions
slide-71
SLIDE 71

71

Outline of GBR (Continued)

  • Analysis Discussion Summary
  • General Design Philosophy
  • Contracting Procurement
  • Specifications and Design Quantities
  • Construction Monitoring Procedures
  • Bridge Foundations
  • MSE Walls
  • Box Culverts
  • Construction Considerations
  • Conclusions and Recommendations

VOLUME II – Current Study Information VOLUME III – Previous Study Information

slide-72
SLIDE 72

72

Client/Owner

  • Missouri Department of Transportation

Design Team Members

  • HNTB Geotechnical and Structural Engineering

Sections

  • Geosystems, L.P.
  • Isherwood Associates
  • Wyllie & Norrish Rock Engineers, Inc.

Specialty Contractor

  • Layne GeoConstruction
slide-73
SLIDE 73

73

QUESTIONS?