---
title: "Aggregate reserve: sandstone N44W/36, 82 m"
subject: "Engineering Geology II"
chapter: 7
key: "semester_4/engineering_geology_ii:reserve-sandstone-n44w-36"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/reserve-sandstone-n44w-36
site: BCT Engineering
---

# Aggregate reserve: sandstone N44W/36, 82 m

Engineering Geology II · Chapter 7: Geology and Construction Materials

- Asked in: 2075 Baisakh, 2 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/reserve-sandstone-n44w-36
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-7

## Question

The attitude of sandstone bedrock is N44°W/36°. The difference of top and bottom of bedrock is 82 m. Calculate the reserve of aggregate in 2.7 km strike length and 0.62 km dip length of rock quarry site.

## Short answer

True thickness = vertical thickness × cos(dip) = 82 cos36° = 66.34 m. Area along bed = 2700 m × 620 m = 1.674×10⁶ m². Reserve = area × true thickness = 1.11×10⁸ m³.

## Answer

**Principle:** reserve = area on the bed $\times$ true thickness, with $t = t_v\cos\delta$.

#### Given
Attitude N44°W/36° (dip $36^\circ$), vertical thickness $t_v = 82$ m, strike length 2.7 km, dip length 0.62 km (along the dip of the bed).

#### Calculation
$$
\begin{aligned}
t &= 82\cos 36^\circ = 66.34\ \text{m} \\
A &= 2700 \times 620 = 1.674 \times 10^6\ \text{m}^2 \\
V &= 1.674 \times 10^6 \times 66.34 = 1.11 \times 10^8\ \text{m}^3
\end{aligned}
$$

**Answer: reserve of aggregate = 1.11 × 10⁸ m³ (about 111 million m³ = 0.111 km³).**

## Check yourself

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

1. Which formula is used for the reserve?
   A. Area x tv sin δ
   B. Area x tv / cos δ
   C. Strike length x dip
   D. Area on the bed x (tv cos δ)
   Answer: D. Volume = area x true thickness. (Key point: Formula)

2. What is the true thickness for tv = 82 m, dip 36°?
   A. About 48.2 m
   B. About 66.3 m
   C. About 101.4 m
   D. About 82 m
   Answer: B. 82 x 0.8090 = 66.34 m. (Key point: True thickness)

3. What reserve results for 2.7 km x 0.62 km?
   A. About 1.37 x 10^8 m³
   B. About 1.67 x 10^6 m³
   C. About 8.1 x 10^7 m³
   D. About 1.11 x 10^8 m³
   Answer: D. 1.674 x 10^6 m² x 66.34 m = 1.11 x 10^8 m³. (Key point: Reserve)

## Close variants set in other exams

- [Aggregate reserve: sandstone N42W/34, 80 m](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Areserve-sandstone-n42w-34) — Engineering Geology II, chapter 7, asked 2×

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