07a - subsurface drainage part 1 (new) - memphis - subsurface... · 2019. 2. 12. · edge drain...
TRANSCRIPT
Subsurface Drainage
Subsurface Drainage
Source: “Making Edge Drains Work,” Better Roads, January 2007
(Untreated orAsphalt Treated)
(Aggregate Filter,Geotextile or ATPB)
Flow from Groundwater
Flow from Groundwater
Flow net slide
Flow from Groundwater
Radius of influence slide
Flow from Groundwater
Radius of influence slide
03.8L H H
Flow from Groundwater
20
1 2
i
k H Hq
L
permeability drawdown
radius ofinfluence
Note that the equation in the book is missing the square!
Flow from Groundwater
Flow from Groundwater
Symmetrical drawdown slide
Flow from Groundwater
Flow from Groundwater
22g
qqW
Two Edge Drains
1 22g
q qqW
One Edge Drain
Example 1
Silty Sand (SM)k = 0.07 ft/day
Flow from Groundwater
Flow from Infiltration
Source: WSDOT Pavement Guide Interactive CD-ROM
Subgrade (Existing Soil)Base / Subbase (Optional)
Crack
Typical Soil Permeability
Flow from Infiltration
c c
i c ps
I Wq N kW C
length of transversecracks/joints
spacing oftransversecracks/joints
number of longitudinalcracks/joints
distance betweenthe outermostlongitudinalcracks/joints
crack/jointinfiltration
rate uncrackedpermeability
Flow from Infiltration
subjected to infiltradesign infiltration rate (volume per day per foot of crack)width of drainage blanket number of contributing longitudinal cracks or jointslength of contributing tran
tion
c
c
c
IWNW sverse cracks or joints
spacing of transverse cracks or jointssC
FHWA Highway Subdrainage Design ManualPublication FHWA‐TS‐80‐224 dated July 1990
Flow from Infiltration
ci L T p
Iq L L kW
avg. length of transverse
cracks/jointsper foot of travel
avg. length oflongitudinalcracks/jointsper foot of travel
distance betweenthe outermostlongitudinalcracks/joints
infiltrationper foot ofcrack/joint uncracked
permeability
Flow from Infiltration
Source: WSDOT Pavement Guide Interactive CD-ROM
Subgrade (Existing Soil)Base / Subbase (Optional)
Crack
1 ft
Flow from Infiltration
It is recommended that the “normal” values of Cs be taken as
the transverse joint spacing for new JPCP and JRCP and as the
anticipated average transverse crack spacing for new CRCP
and asphalt concrete pavements. A value of 40 feet has been
suggested for new asphalt pavements; however “normal”
transverse cracking as a result of thermal and moisture
changes can be extremely variable.
FHWA Highway Subdrainage Design ManualPublication FHWA‐TS‐80‐224 dated July 1990
Example 1 (Continued)
Silty Sand (SM)k = 0.07 ft/day
Example 2
Artesian Flow
0
a
k HqH
Excesshydraulichead
Example 3
Flow due to Spring Thaw
Flow due to Spring Thaw
Flow due to Spring Thaw
Flow due to Spring Thaw
Example 1 (Continued)
Silty Sand (SM)k = 0.07 ft/day
Flow due to Spring Thaw
Flow due to Spring Thaw
Drainage Blanket Design Flow
max , , n i g a mq q q q q
Edge Drain Design Flow
1 d nq q q WOne Edge Drain
1 2 d n
Wq q qTwo Edge Drains