Drainage System Calculation MASMA
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Transcript of Drainage System Calculation MASMA
BUILDING
Area = 221.57m2,Perimeter = 64 mFrom table 13.A1, minor system design ARI = 5 years (Terengganu, Kuala Dungun )
Table 13.A1 Coefficients for the IDF Equations for the Different Major Cities and Towns inMalaysia (30 t 1000 min)
Determine tc :
Overland flow =32 mCatchment area average slope = 0.5%From design chart 14.1 for bare soil surface, to = 13.5 ~ 8 minDrain length = 64mAssume, v = 1.0 m/s
td = L/V = 64/1.0 = 64 s = 1.07 min
Total tc = to + td
= 8 + 1.07 =9.07~ 10 min
Determine I and C :
t = 30
ln (5I30) = a + b (ln t) + c (ln t2) + d (ln t3)= 5.5077- 0.0310(ln 30) – 0.0899(ln 30)2 +0.0050(ln 30)3
= 4.559 mm/hr(5I30) =95.49 / 2 mm/hr P30 =47.75mm
t = 60
ln (5I60) = a + b (ln t) + c (ln t2) + d (ln t3)= 5.5077 – 0.0310 (ln 60) -0.0899(ln 60)2 +0.0050 (ln 60)3
= 4.217 (5I60) =4.217 mm/hrP60=67.83mm
Rainfall depth
Using Equation 13.3
Pd= P30 – FD ( P60 - P30 )= 47.75 mm –1.28(67.83mm - 47.75 mm) =22.05 mm
where,
Pd = design rainfall depth
P30, P60 = 30 and 60 minutes duration rainfall depths respectively
FD = adjustment factor for storm duration from Table 13.3
To determine FD :
1) Determination of tc byrefer to Design Chart 14.1
Length of overland flow (m) = 32 m
Average surface slopes = 0.5%
tc = 10 min
2) Value of FD for Equation 13.3, from Table 13.3 – East Coast
FD = 1.28
Intensity
Equation 13.4, I = Pd / d
=22.05mm/(10/60)
=132.3mm/hr
Determination of Qy
Qy = C y I EA
360
where,
Runoff coefficient, C = 0.83
Refer Design Chart 14.3, Category 3
Intensity, I =132.3 mm/hr ~ 133 mm/hr
Drainage area, A = 221.57m2= 0.0548ha
Peak Flow for 5 year ARI :
Qy = C y I EA
360
= (0.83 x 133 x 0.0548)
360
= 0.016 m
3
/s
Proposed Building Perimeter Drain Section
0.45 m
0.45 m
Check :
Area of build up drain section, A = 0.2025 m2
Wetted perimeter of drain section, P = 1.35m
R = A/P = 0.2025/1.35= 0.15
S = 1 : 300 = 0.003
Manning coefficient, n = 0.04
Therefore, Qcapacity= 1.49AR2/3 S1/2 / n
= 1.49 (0.2025)(0.15) 2/3 (0.003) 1/2 / 0.04
= 0.116m3/s
Qdischarge<Qcapacity
0.016 m3/s <0.116 m3/s OK!
BOUNDRY
Area = 32000m2, Perimeter = 800mFrom table 13.A1, minor system design ARI = 5 years (Johor Bahru, Johor )
Determine tc :
Overland flow =400 mCatchment area average slope = 0.5%From design chart 14.1 for bare soil surface, to = 8 minDrain length = 800m
Assume, v = 1.0 m/std = L/V = 800m /1.0 = 800s = 13.3 min ~ 14min
Total tc = to + td
= 8 + 14 =22 min
Determine I and C :
t = 30
ln (5I30) = a + b (ln t) + c (ln t2) + d (ln t3)= 5.5077- 0.0310(ln 30) - 0.0899(ln 30)2 +0.0050(ln 30)3
= 4.559 mm/hr(5I30) = 95.49 / 2 mm/hr P30 = 47.74 mm
t = 60
ln (5I60) = a + b (ln t) + c (ln t2) + d (ln t3)= 5.5077 – 0.0310(ln 60) – 0.0899(ln 60)2 +0.0050(ln 60)3
= 4.217 (5I60) = 67.83mm/hrP60=67.83mm
Rainfall depth
Using Equation 13.3
Pd = P30 – FD ( P60 - P30 )
= 47.74 mm - 0.376(67.83mm-47.74 mm)
=40.19mm
where,
Pd = design rainfall depth
P30, P60 = 30 and 60 minutes duration rainfall depths respectively
FD = adjustment factor for storm duration from Table 13.3
To determine FD :
Determination of tc byrefer to Design Chart 14.1
Length of overland flow (m) = 400 m
Average surface slopes = 0.5%
tc = 22 min
Value of FD for Equation 13.3, from Table 13.3 – East Coast
FD = 0.376
Intensity
Equation 13.4, I22 = Pd / d
= 40.19/(22/60)
= 109.61 mm/hr
Determination of Qy
Qy = C y I EA
360
where,
Runoff coefficient, C = 0.8
Refer Design Chart 14.3, Category 3
Intensity, I = 40.19mm/hr ~ 41mm/hr
Drainage area, A = 32000m2 = 7.907 ha
Peak Flow for 2 year ARI :
Qy = C y I EA
360
= (0.80 x 41 x 7.90)
360
= 0.72 m
3
/s
Proposed Remaining Road Drain Section
Type of channel = bare soil surfaceManning coefficient, n = 0.04Slope gradient, So = 1:300 = 0.003Proposed U drain = 1000 x 1000 mm
1m
1m
where,
Cross sectional area channel, A = 1 m × 1 m = 1 m2
Hydraulic Radius, R = A/P = (1/3) = 0.33 m
Slope of drain, S = 1:300
Manning’s roughness coefficient, n = 0.04
Flow :
Therefore, Qcapacity = 1.49AR2/3 S1/2 / n
= 1.49 (1.0)(0.33) 2/3 (0.003) 1/2 / 0.04
= 0.974m3/s
Qdischarge<Qcapacity
0.72 m3/s <0.974 m3/s OK!
As a conclusion, this drain is adequate to cater for the overall requirement
Q = 1.49 A R2/3S1/2 / n
Proposed Size of Drain Sump
Drain sump basically acting as a connection for all the drainage. Sump is defined as a drain consisting of an outer tube which is vented to the outside with a smaller tube within it that is attached to a suction pump. Both tube have multiple perforations that allows fluid and air to be carried away through the suction tube.
Refer to road and drainage plan for the proposed location for all the drain sump.
Maximum flow from the drainage, Q = 0.639m3/s
The velocity of water flow in drain, v = Q/A = 0.639 / 0.25
= 2.56 m/s
Calculation size of sump
The width of drainage size = 0.50 m
The length => 0.25 m2 / 0.5 m = 0.50 m
The minimum size of sump:
Length = 0.50 m
Width = 0.50 m
Depth = 0.50 m
Thus, the minimum size of sump is 500mm×500mm
Therefore, the propose size of sump is 1100mm×1100mm according to standard size.
Refers to road and drainage plan for the detailing sump.