Constructability Reviews Minimize the Need for Drilled Shaft Remediation and Repair

1
Constructability Reviews - Minimize the Need for
Drilled Shaft Remediation and Repair
Caltrans / ADSC CIDH Pile Workshop
ADSC The International Association of Foundation
Drilling Pacific Center 1 14180 Dallas
Parkway, Suite 510 Dallas, TX. 65254 Telephone
214-343-2091 Fax [phone] WWW.ADSC-IAFD.CO
M
PRESENTED BY JOHN J. ROE, P.E.
2
Outline

• What Causes Problems with CIDH Piles?

• How Can We Reduce Anomalies and Defects in
  CIDH Piles?

• Constructability Reviews Can Be a Win- Win
  Solution for All !!!

3
What Causes Problems in Drilled Shafts?

• Difficult Geologic Conditions / Insufficient
  Soils Information

• Design Problems

• Poor Construction Practices

4

• Difficult Geologic Conditions

• Are the Easy Sites All Gone?

• Cobbles and Boulders

• Weak Caving Soils

• High Groundwater

• Changed Conditions

5

• Project Soils Information (Cont.)

• Complete Investigation

• Rock Strength Data (Not Ranges)

• Groundwater Data

• Drill Logs Handwritten Logs

• Drill Cores

• Eliminate Exculpatory Clauses

6

• Additional Exploratory Information (Cont.)

• Small Diameter Borings at Each Bent Location

• Large Diameter Test Shaft

• Bid Item / Contractor Investigation

7

• Design Problems

• Insufficient Rebar Spacing in Cages

• Overly Large Aggregate

• Multiple Layers of Reinforcing

• Insufficient Concrete Coverage

8
Rebar Cage Couplers and Inspection Pipes Can
Restrict Flow of Concrete
Rebar Too Tightly Spaced !!!
9
Sufficient Concrete Cover
Design Must Allow for Tolerances
10
Socket Permanent Casing into Competent Rock Not
Caving Rock that Acts like Soil
11
Seal Course
Use of Rock Sockets with Casing
12
Best Practices / Pre-Bid Checklist

• Review All Documents

• Conflicts / Ambiguities

• Pre-Bid Notifications

• Special Requirements

• Risk Assessment

• Constructability

• Construction Tolerances

13
Best Practices / Site Visit

• Access

• Site Hazard Analysis

• Photographs

• Geologic Features

• Equipment Requirements

14

• Poor Construction Practices

• Inappropriate Concrete Mix Designs

• Inexperienced Drill Crews

• Inappropriate Equipment

• Faulty Slurry Management Techniques

• Improper Cage Handling

15

• Poor Construction Practices (Cont.)

• Inadequate Cleaning of the Bottom of Shaft

• Insufficient Wasting of Contaminated Concrete
  at the Top of Shaft

• Constructing the Shaft Too Rapidly

• Problems Associated with the Tremie

16
Concrete Mix Design Standardize Regionally

• 3/8 or 1/2 Max. Aggregate

• 7-9 Slump

• Flowable

• Minimize Bleed Water

• Minimize Segregation

• Restrict Early / Flash Set

17
Shaft Drilling Considerations

• Proper Slurry Techniques

• Sufficient Fluid Head

• Drilling in the Dry

• Telescoping Casing

• Drill Slowly Minimize Suction Created by the
  Tool

• Minimize Over Drilling the Bottom

18
Size the Equipment to Meet Job Requirements
Soilmech-825 Drill Unit
Medium Size Drill Unit
19
Wet-Method Drilling Special Considerations
Exiting Shaft with Bucket
20
Hydrate the Polymer Slurry
Baker Tanks
Proper Slurry Management
21
Maintain Sufficient Head
Slurry Piping into Shaft
22
Drilling Operations
23
Four Tests Required
Slurry Testing Equipment
24
pH Testing
25
Mud Density
26
Viscosity
27
Sand Content
28
Slurry Test Report (Per Specifications)
29
Shaft Cleaning Considerations

• Clean-out Bucket

• Bottom (Over Drilling)

• Hydraulic Pump

• Airlift

• Sand Content

• Silt/Clay Content (Exchange the Slurry)

30
Rebar Cage Placement

• PVC Tube Stabilizers

• Record Coupler Locations

• Internal Bracing

• Centralizers / Dobbies

• Record Rebar Splices and Significant
  Concentrations

31
Stabilization Rods
Install PVC Tubes with Rods
32
Log Tube Coupler Locations
33
Internally Braced
Engineered for Lifting
Lifting the Rebar Cage
34
Rebar Cage Suspended Overhead
35
Light-Weight Centralizers
Install Roller Spacer Assemblies (Centralizers)
36
Centralizers
Template in Place
37
Chain Binders
Tie-Off Rebar Cage
38
Template
Rebar Cage Tied Off In Place to Template
39
Tremie Considerations

• Check for Seal Leaks at Joints

• Ball / Pig

• Cap

• Disallow Milking

• Maintain Tremie within the Concrete

40
10 to 16 Diameter
Mobile Tremie Rack
41
Sectional Tremie
Installation of Tremie Pipe
42
Concrete Placement

• Check for Slump / Segregation

• Significant Interruption in Concrete Pour
  Deliveries

• Problems Stop!

43
Concrete Chute
Check for Segregation of Paste from Aggregate
44
Concrete Pump
Concrete Pumping
45
Concrete Pump
Tremie Pipe
Concrete Pumping
46
Baker Tank
Submersible Pump
Pump Slurry Back to Tank as Concrete is Placed
47
Equal Level of Level of Concrete
Concrete Flowing Outside Cage
48
Weighted Tape Measure
Measure Depth of Concrete
49
Lift Casing During Concrete Pour
50
Removal of Casing
51
Remove Template
52
Do Not Vibrate Top of Concrete
53
Concrete Placement Log
54
Fill Tubes with Water (Warm)
55
Cleaning the Top of Shaft

• Over-pour Concrete

• Remove All Laitance

• Remove Stabilizer Bars

• Fill PVC Tubes with Water

• Access for NDT Testing

56
How Can We Reduce Anomalies and Defects in
Drilled Shafts?
57
Team Approach

• Design Phase

ADSC and Caltrans

• Quality Control

• Quality Assurance

• Training/Education

• Improved Construction Techniques

• Constructability Reviews

58
Constructability Reviews Win-Win

• Specification Conflicts

• Soils Information

• Drawings

• Rebar Cage Configuration

• Construction Joints

• Rock Sockets

• Permanent Casing

• Construction Tolerances

59
Team Approach Results

• Quality Product

• More Competitive Bids

• Reduced Bid Prices

• Minimize Delays

• Reduce Construction Claims

60
QUESTIONS ???
QUESTIONS ???
COMMENTS ???