Design Information Bulletin 73 (DIB 73)
Design Information Bulletin Number 73 (DIB 73) - Slab Replacements With Existing Edge Drains - This DIB provides guidelines to designers for PCCP slab replacements with existing edge drains.
State of California
Business, Transportation and Housing Agency
||Deputy District Directors,
Project Development and
Ken Bandow, Central Design
|November 1, 1988
||DEPARTMENT OF TRANSPORTATION
Division of Project Development - Office of Project Planning and Design
||Design Bulletin No. 73 - Slab Replacements with Existing Edge Drains
We are transmitting Design Bulletin No. 73, Slab Replacements with Existing Edge Drains, to assist the designer. A proposed specification for slab replacements with existing edge drains has been submitted to Office of Office Engineer for publication.
This subject will be included in the next revision of the Highway Design Manual
Please reproduce the Design Bulletin and distribute to all Design Manual holders.
DEAN LARSON, Acting Chief
Office of Project Planning and Design
DESIGN INFORMATION BULLETIN NO. 73 -
PORTLAND CEMENT CONCRETE PAVEMENT (PCCP) SLAB REPLACEMENTS WITH EXISTING EDGE DRAINS
The objective of this design bulletin is to provide guidelines to designers for PCCP slab replacements with existing edge drains.
A problem is occurring with full depth PCCP slab replacement when side form(s) have to be placed where the existing edge drain is located in the shoulder. If the edge drain is replaced, the edge drain flow line will be too high to intercept water at the slab/subgrade interface. Water will flow to the bottom of the full depth slab, allowing pumping of the unbound subgrade material which may result in early slab distress and/or plugging of the edge drain. Each slab replacement location could require a new vent and outlet for the existing system and a new vent and outlet for the lower new edge drain, which is not recommended.
III. SLAB REPLACEMENT
Excavate and remove the treated permeable material (TPM) and edge drain, expose the edge drain approximately one foot past each end of the slab to be removed, place the side form(s) and place the full depth PCCP slab. Remove side form(s) after curing and place and compact commercial quality Class 2 aggregate base in the excavation for the side form(s) to the grade of the bottom of the existing edge drain stubs. Attach an unslotted PVC pipe to the existing slotted edge drains using band couplers. Place and compact additional commercial quality Class 2 aggregate base around and over the top of the unslotted PVC pipe to within 0.25' of the top of the new PCCP slab. Backfill the remainder of the excavation with 0.25' of dense graded AC. See attached sketch.