VIPSolutions1. Design Problem: A Sarda fall for a channel is carrying 24 m3/s of water at a depth of flow equal to 1.8 m. The bed width of the channel is 20 m. The following data is associated with the fall: us DIS FSL (m) 118.20 117.00 Drop (m) 1.20 Bed level (m) 116.40 115.20 (a) Design the dimensions of the crest and cistern downstream of the fall (b) Design the floor on the basis of Bligh's creep theory, considering coefficient of creep= 8.
Question:
1. Design Problem: A Sarda fall for a channel is carrying 24 m3/s of water at a depth of flow
equal to 1.8 m. The bed width of the channel is 20 m. The following data is associated with the
fall:
us DIS
FSL (m) 118.20 117.00
Drop (m) 1.20
Bed level (m) 116.40 115.20
(a) Design the dimensions of the crest and cistern downstream of the fall
(b) Design the floor on the basis of Bligh's creep theory, considering coefficient of creep= 8.
This is AI generated Response.
Asked by: Test User 100259
Created at: 2025-05-12 18:43:37
Asked by: Test User 100259
Created at: 2025-05-12 18:43:37
Final Answer:
Rendered
Raw Text
Did you like this answer?
Let's break down the problem step by step for clear understanding and calculation.
---
## Given Data:
- **Discharge (Q):** 24 m³/s
- **Depth of flow (h):** 1.8 m
- **Bed width (b):** 20 m
- **Upstream FSL:** 118.20 m
- **Downstream FSL:** 117.00 m
- **Drop:** 1.20 m
- **Upstream Bed Level:** 116.40 m
- **Downstream Bed Level:** 115.20 m
- **Bligh’s Coefficient of Creep (C):** 8
---
## (a) Design the dimensions of the crest and cistern downstream of the fall
### **1. Crest Length and Width:**
For Sarda falls (rectangular crest):
- **Length of crest (L):** Generally taken as the bed width of the channel = 20 m
- **Width of crest (W):**
- Standard practice: width = 0.6 to 0.75 × depth of water over the crest
- Let’s calculate depth over crest:
#### **Head over crest (H):**
Usually, water depth over crest = depth of flow = **1.8 m**
#### **Width of Crest (W):**
\[
W = 0.6 \times 1.8 = 1.08 \text{ m} \quad \text{to} \quad 0.75 \times 1.8 = 1.35 \text{ m}
\]
**Adopt:** \( W = 1.2 \) m (average value)
---
### **2. Cistern Design (Downstream):**
- **Depth of cistern (d):** 1/4th of drop = \( \frac{1.2}{4} = 0.3 \) m
- **Length of cistern (l):** 4 to 5 times the depth of cistern = \( 4 \times 0.3 = 1.2 \) m to \( 5 \times 0.3 = 1.5 \) m
**Adopt:** \( l = 1.3 \) m
---
### **Summary Table:**
| Parameter | Value |
|-----------------------|--------------|
| Crest Length (L) | 20 m |
| Crest Width (W) | 1.2 m |
| Cistern Depth (d) | 0.3 m |
| Cistern Length (l) | 1.3 m |
---
## (b) Design the floor on the basis of Bligh’s Creep Theory
### **Bligh's Creep Theory:**
- **Total Creep Length (L):**
\[
L = C \times H
\]
Where,
- \( L \) = Total length of creep (floor length)
- \( C \) = Coefficient of creep (= 8)
- \( H \) = Head difference (Drop) = 1.2 m
\[
L = 8 \times 1.2 = 9.6 \text{ m}
\]
**So, the length of the floor should be at least 9.6 m.**
---
### **Summary of Solution:**
#### (a) **Crest and Cistern Dimensions:**
- Crest Length: **20 m**
- Crest Width: **1.2 m**
- Cistern Depth: **0.3 m**
- Cistern Length: **1.3 m**
#### (b) **Floor Length as per Bligh’s Creep Theory:**
- **Floor Length:** **9.6 m**
---
**If you need detailed drawings or further explanation, let me know!**
📢 Instructions:
- Ask anything relatd to above question only.
- For new Question goto :