Manual Notice: 2020-1
From: Graham Bettis, P.E., Director, Bridge Division
Manual: Geotechnical Manual
Effective Date: July 13, 2020
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This manual provides policy for geotechnical investigation and design for project development.
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The revisions contained in each chapter of this version are to clarify the policy and high-level procedures published in 2018. Generally, revisions to the manual were to:
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- Update information in Chapter 2 regarding investigation around suspected karst formations, and provide more guidance when recording groundwater elevations during drilling operations.
- Make minor changes to the laboratory testing protocol for shear strength determination in Chapter 2.
- Update procedure in Chapter 3 on ‘Drill Hole Filling’ with current standard practices using mix of bentonite and/or grout.
- Include limits of any needed Temporary Special Shoring in Retaining Wall layouts standard specifications which would apply to Temporary Special Shoring in Chapter 6.
- Eliminate prior soil parameter assumptions on nailed embankments to account for independent analysis of wall systems in Chapter 6.
- Highlight in Chapter 6 the importance of utilizing proper parameters in the RW(MSE)DD sheet to standardize design.
- Update the minimum criteria for nail diameters in rock nailed walls section in Chapter 6.
- Provide greater clarification in Chapter 7 that global stability design factors of safety should be at minimum 1.3 and 1.5.
Chapter 5 underwent significant revisions and updates, which include:
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- geologic layer terminology clarification in Sections 1 and 2;
- updating guidance for Scour Summary Sheet and submission of Form 2605 into the bridge inspection system;
- updating method for calculating scour at bridge channels including reference to NCHRP reports;
- updating the scour guidance at bridge class culverts.
Supersedes
The revised manual supersedes prior versions of the manual.
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For more information about any portion of this manual, please contact the TxDOT Bridge Division.
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Past manual notices are available in a PDF archive.