GEO3701 Project Year Geology for Engineers 2026

UNIVERSITY OF SOUTH AFRICA
College of Agriculture and Environmental Sciences


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GEO3701: Engineering Geology
Geotechnical Desktop Study for the Proposed Dam and
Reservoir Development at Ga-Mathipa/Ragopola, Fetakgomo-
Tubatse Local Municipality, Limpopo Province, South Africa

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GEO3701
Module Code:

Engineering Geology
Module Name:

Geotechnical Desktop Study — Proposed
Assignment Topic: Dam and Reservoir, Ga-Mathipa/Ragopola

Project Year 2026
Project:




Submitted in partial fulfilment of the require-
ments for Engineering Geology (GEO3701), UNISA

,Declaration

I hereby declare that the project work entitled “Geotechnical Desktop Study for the Proposed
Dam and Reservoir Development at Ga-Mathipa/Ragopola, Fetakgomo-Tubatse Local Munici-
pality, Limpopo Province, South Africa” is a record of an original work done by me. The results
embodied in this report have not been submitted to any other university or institute for the
award of any degree or diploma.




Name. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surname. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .




Student Number. . . . . . . . . . . . . . . . . . . . . . . . Contact Number. . . . . . . . . . . . . . . . . . . . . . . . . . . .




Signature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Date.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

,Contents


Declaration 2


1 Introduction 5


2 Site Description 7


3 Climatic (Weinert Area) and Topographic Data 8

3.1 3.1 Climatic Conditions and Weinert N-Value . . . . . . . . . . . . . . . . . . . . 8

3.2 3.2 Topographic Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9


4 Identification of Geology 11


5 Identification of Problem Soils/Geology 13

5.1 5.1 Expansive (Active) Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.2 5.2 Collapsible Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.3 5.3 Dispersive Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.4 5.4 Soft and Compressible Alluvial Soils . . . . . . . . . . . . . . . . . . . . . . . 14


6 Assessment of Discontinuities and their Engineering Implications 15


7 Field and Laboratory Investigation Proposal 17

7.1 7.1 Site Reconnaissance and Geological Mapping . . . . . . . . . . . . . . . . . . 17

7.2 7.2 Geophysical Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7.3 7.3 Trial Pits, Boreholes and In-Situ Testing . . . . . . . . . . . . . . . . . . . . . 18


8 Occupational Health and Safety (OHS) Requirements 20


9 Environmental Consideration 21

,10 Conclusions and Recommendations 22


Reference List 24

, 1 Introduction

The successful planning and design of civil engineering infrastructure depends on a thorough
understanding of the geological conditions present at a proposed site. Engineering geology
applies geological principles to engineering practice by identifying and evaluating rock for-
mations, soil characteristics, groundwater conditions, geological structures and potential
geohazards that influence the safety, stability and long-term performance of engineering
works (Wessels, 2021). Because every engineering structure is founded on or within soil and
rock, geological investigation is an essential component of project planning, site selection,
design and construction. An understanding of the geological setting allows the engineer to
identify constraints during the planning and design stages and to implement appropriate mit-
igation measures so that residual engineering risk is reduced to an acceptable level (Brink,
1979).

This report presents a geotechnical desktop study for the proposed construction of a small
dam and reservoir in the Ga-Mathipa/Ragopola area, within the Fetakgomo-Tubatse Local
Municipality of Limpopo Province. The dam is intended to provide a reliable domestic water
supply to the surrounding rural communities while supporting small-scale irrigation. The
performance of any dam depends primarily on the competence of the foundation materials
in the dam wall and on the geological conditions of the reservoir basin. Rock type, degree
of weathering, discontinuities, groundwater regime, permeability, faulting and the presence
of problem soils all influence foundation stability, seepage losses and the overall safety of
the structure (Bell and Maud, 1994). Geological investigation therefore assists the design
engineer in anticipating hazards, evaluating material properties and selecting design and
construction methods suited to the site.

A desktop study is the first stage of any site investigation and is undertaken before the more
expensive stages of fieldwork are commissioned. Existing geological maps, topographical
data, aerial and satellite imagery, climatic records and published literature are reviewed to
identify the likely geological formations, engineering constraints and probable behaviour of
the soils and rock mass at the site. This preliminary assessment allows the investigating
team to plan a focused programme of subsurface investigation, comprising borehole drilling,
trial pitting, laboratory testing and, where required, geophysical surveying, so that resources
are directed at the specific risks the desktop review has identified (South African Institute
of Engineering Geologists (SAIEG), 1997). The findings of this study are preliminary and are
intended to inform, rather than replace, the detailed field and laboratory investigation recom-