---
title: "Khosla's simple profiles and corrections"
subject: "Irrigation and Drainage Engineering"
chapter: 5
key: "semester_6/irrigation_and_drainage_engineering:khosla-simple-profiles-corrections"
source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/khosla-simple-profiles-corrections
site: BCT Engineering
---

# Khosla's simple profiles and corrections

Irrigation and Drainage Engineering · Chapter 5: Diversion Headworks

- Asked in: 2066 Bhadra (old course), 3+3 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/khosla-simple-profiles-corrections
- Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-5

## Question

Draw four (4) simple Khosla's profiles for a weir of complex profiles. What corrections Khosla suggested to accommodate such simplifications?

## Short answer

Four simple profiles: pile at upstream end, pile at downstream end, depressed floor, and intermediate pile. Corrections: mutual interference C = 19√(D/b')((d+D)/b)% (positive upstream, negative downstream); floor thickness correction = (φD - φE)/d × t; slope correction from table (e.g., 11.2% for 1:1) multiplied by horizontal slope length over pile distance.

## Answer

#### Four simple Khosla profiles

Khosla's equations exist for simple forms into which a complex weir profile is broken down:

```text
(a) Pile at the upstream end    (b) Pile at the downstream end
 ~~~|                            ~~~~~~~~~~~~~~|
 ___|_______________              _____________|__
    |                                          |
    d  (E1,D1,C1)                              d (E2,D2,C2)

(c) Depressed floor             (d) Intermediate pile
 ~~~ __     ___________          ~~~  ______|_______
 ___/  \___/                     ___/       |
        |                                    d
```

(a) a horizontal floor with a pile at its **upstream end**; (b) a horizontal floor with a pile at its **downstream end**; (c) a **depressed floor** (a horizontal floor lowered below the river bed, the depression acting like a short pile); (d) a floor with an **intermediate pile**. Their pressures at the key points (E, D, C) are given by Khosla's formulas in terms of $\alpha = b/d$ and $\lambda$.

#### Corrections suggested by Khosla

1. **Correction for mutual interference of piles** – when a pile of depth $d$ is influenced by another pile of depth $D$ at a distance $b'$ (total floor length $b$):

$$
C = 19\sqrt{\frac{D}{b'}}\left(\frac{d+D}{b}\right)\ \%
$$

It is positive for points upstream of the interfering pile and negative for points downstream of it.

2. **Correction for thickness of the floor** – the key points are taken at the floor top, while the uplift acts on the underside; the pressure is interpolated linearly between the point at floor level and the pile tip:

$$
\text{Correction} = \frac{\phi_D - \phi_E}{d}\,t
$$

(positive at the u/s pile's $C_1$, negative at the d/s pile's $E_2$).

3. **Correction for the slope of the floor** – a sloping floor (glacis) differs from the horizontal floor of the simple profile. A correction factor from a table (e.g. 11.2% for 1:1, 6.5% for 2:1, 4.5% for 3:1, 3.3% for 4:1) is multiplied by the ratio of the horizontal length of the slope to the distance between the two pile lines between which the slope lies. It is positive for a down slope and negative for an up slope in the direction of flow.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which set lists Khosla's simple profiles?
   A. Pile at u/s end, pile at d/s end, depressed floor, intermediate pile
   B. Only u/s and d/s piles
   C. Glacis, crest, cistern and apron
   D. Pile at u/s end, d/s apron, blocks, filter
   Answer: A. A complex weir is broken into these four simple forms for which Khosla gave formulas. (Key point: Four simple profiles)

2. The correction for mutual interference of piles is applied for the pile that is:
   A. Positive for the pile downstream of the interfering pile
   B. Negative for the pile upstream of the interfering pile
   C. Positive for the upstream pile and negative for the downstream pile
   D. Always negative
   Answer: C. Interference raises the pressure at the pile upstream of the interfering pile (positive) and lowers it at the downstream pile (negative). (Key point: Mutual interference)

3. Why is a correction for floor thickness needed?
   A. Key points are at the floor top while uplift acts at the underside
   B. Thick floors have no uplift
   C. Piles are shorter in thick floors
   D. The exit gradient depends on thickness only
   Answer: A. The key points are taken at the floor top, but uplift acts on the floor underside, so pressure is interpolated linearly. (Key point: Thickness correction)

4. The slope correction (e.g. 6.5% for 2:1) is multiplied by the ratio of slope length to total floor length and is:
   A. Negative for a down slope, positive for an up slope
   B. Positive for a down slope, negative for an up slope in the flow direction
   C. Always positive
   D. Always negative
   Answer: B. The correction is added for a down slope and subtracted for an up slope in the direction of flow. (Key point: Slope correction)

## Related in Irrigation and Drainage Engineering

- [Diversion weir: Bligh and Khosla, 4000 m3/s](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Adiversion-weir-bligh-khosla-q4000) — Irrigation and Drainage Engineering, chapter 5
- [Khosla: percentage pressure and piping, pond 503](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Akhosla-floor-piping-abcd-503) — Irrigation and Drainage Engineering, chapter 5
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