---
title: "Drilling type and field tests, Kathmandu core"
subject: "Foundation Engineering"
chapter: 2
key: "semester_5/foundation_engineering:drilling-field-tests-kathmandu"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/drilling-field-tests-kathmandu
site: BCT Engineering
---

# Drilling type and field tests, Kathmandu core

Foundation Engineering · Chapter 2: Soil Exploration

- Asked in: 2075 Asoj, 5 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/drilling-field-tests-kathmandu
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-2

## Question

In a core of Kathmandu valley a geotechnical investigation is to be carried out. As an engineer, recommend the type of drilling and the suitable field tests such that the test data can be used as much as possible.

## Short answer

Rotary wash boring with casing and bentonite is recommended for the soft lake clays and sands. Suitable field tests: SPT every 1.5 m, electric cone penetration with pore pressure (CPTu) for continuous profiling, field vane shear in soft clay, and shear-wave velocity measurement, complemented by laboratory consolidation and triaxial tests.

## Answer

**Site nature:** Kathmandu valley is a lacustrine basin filled with soft to stiff lake clays and silts, fine micaceous sands, thin peat/black clay and gravelly layers, with high groundwater table, low strength at shallow depth and high liquefaction/amplification risk.

#### Recommended drilling
- **Rotary (wash) boring with casing and bentonite mud** to the required depth (15-30 m or more), because soft clay and sand below water table would collapse in simple augering; percussion is not recommended for disturbance.
- Use a thin-walled piston (Shelby) sampler in clay/silt for undisturbed samples and split-spoon sampling in sands.

#### Suitable field tests
| Test | Where | Data obtained |
|---|---|---|
| SPT (every 1.5 m) | sand, silt, stiff clay | $N$, $\phi$, density, liquefaction, bearing capacity |
| Electric cone penetration test with pore pressure (CPTu) | whole profile, good for soft clay and silt | continuous profile, $q_c$, $f_s$, $u$, undrained strength, layering |
| Field vane shear | soft clay | undrained strength $c_u$ and sensitivity |
| Groundwater observation / pore pressure | all holes | seasonal water level |
| Shear-wave velocity (downhole/MASW) | seismic design | site class, amplification |

Laboratory tests (consolidation, triaxial/UCS, Atterberg limits) on the undisturbed samples complement these. CPTu and SPT give the greatest amount of directly usable design data for bearing capacity, settlement of soft clay, pile capacity and liquefaction.

## Check yourself

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

1. Kathmandu valley soil is mainly
   A. hard granite at surface
   B. dry dune sand
   C. soft to stiff lake clays and silts with high groundwater and liquefaction risk
   D. dense glacial till
   Answer: C. It is a lacustrine basin. (Key point: Soil nature)

2. The recommended drilling is
   A. simple dry augering
   B. rotary wash boring with casing and bentonite mud
   C. percussion
   D. hand digging only
   Answer: B. Soft clay and sand below the water table would collapse in simple augering. (Key point: Drilling)

3. CPTu is recommended because it
   A. gives only visual samples
   B. works only in rock
   C. gives a continuous profile of qc, fs and pore pressure in soft clay and silt
   D. measures only water colour
   Answer: C. It gives layering and undrained strength. (Key point: CPTu)

4. Shear-wave velocity (downhole/MASW) is used for
   A. measuring grain size
   B. finding liquid limit
   C. pile driving
   D. site class and amplification in seismic design
   Answer: D. It helps assess seismic response. (Key point: Seismic)

## Related in Foundation Engineering

- [Field tests and SPT corrections for sand](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Afield-tests-spt-corrections) — Foundation Engineering, chapter 2, asked 2×
- [Investigation details for bridge foundation](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abridge-foundation-investigation) — Foundation Engineering, chapter 2
- [Pressuremeter test features](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Apressuremeter-distinctive) — Foundation Engineering, chapter 2
- [Standard penetration test and corrections](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aspt-procedure-corrections) — Foundation Engineering, chapter 2, asked 3×
- [Limitations of plate load test](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aplate-load-test-limitations) — Foundation Engineering, chapter 6, asked 5×
- [Footing size from plate load test curve](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aplate-load-footing-size-3200kn) — Foundation Engineering, chapter 6

## Related in other subjects

- [Phase with supplementary core drilling](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Acore-drilling-phase) — Engineering Geology II, chapter 4
- [Report on sound pollution in Kathmandu Valley](https://www.bctengineer.com/question.md?key=semester_5%2Fcommunication_english%3Areport-sound-pollution-kathmandu) — Communication English, chapter 9
- [Core cutter field density numerical](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Acore-cutter-density-numerical) — Soil Mechanics, chapter 2
- [Shear strength tests (lab and field)](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Ashear-strength-tests-names) — Soil Mechanics, chapter 10, asked 3×