The Geotechnical Engineering Division undertakes research and consulting services, which include site investigations to obtain ground parameters for economic and safe design and construction of civil engineering structures.
The primary objectives of the division are:
(a) to provide an adequate analytical and numerical framework within which the observational skills of the professional geotechnical engineer can be harnessed to produce information that will be immediately useful in engineering design procedures;
(b) to underline the importance of water and particularly groundwater as an economic asset to be conserved and as a problem in ground engineering design.
(c) To identify departures from an ideal material behavior which may initiate design difficulties and high pre-construction costs Such departures include the following:
• Weak and/or compressible materials, e.g.
Closely jointed rock
Saturated fine sands
• Deep overburden (completely weathering rock at depth).
• Irregular rockhead (uneven/non-uniform weathered with heterogeneous engineering properties).
• High permeability associated with high water level (e.g. flood plain).
• Ground movements - Subsidence
- Landslides & rock falls
- Slope instabilities
•Occurrence of deleterious minerals.
In essence, the anisotropic and in-homogeneity characteristics of the earth materials are be adequately investigated prior to design and construction.
Areas of Specialization
The major activities of the division are the following:
i). Sub-soil investigations for foundation design of all civil works;
ii). Slope stability studies;
iii). Studies on mitigation of earthquake and other geological hazards;
iv). Coastal displacement and shore line control studies;
v). Geo-technical evaluation of road construction materials;
vi). Construction materials improvement ( stabilization studies);
vii). Investigation of post construction failures of building foundations.
Site investigations involve the following:
- test pit excavation
- boring (percussion and rotary)
- Standard penetration test
- Dynamic cone penetration
- Shear vane tests
- Disturbed samples
- Undisturbed samples
- Water samples - pH, Cl, SO4, Organic content tests.
- Soil classification
- Shear strength parameters (cohesion & friction angle)
- Consolidation and settlement parameter
Salient factors which are investigated include the following:
•Topography of the terrain
•Distribution of the strength, deformability, permeability, chemical stability of the foundation in quantitative, qualitative and geometric terms.
•Availability of quality construction materials.
•Water tightness (especially for dams)
•Valley sides stability
•Socio-economic constraints (e.g. development of landfills)
Some salient issues are also highlighted in site investigation reports . These include the following:
i) general description of the site
ii) general geology of the area and the site
iii) description of soil conditions found in bore holes and trial pits
iv) discussion of groundwater situation
v) laboratory test results
vi) discussion of results of investigation in relation to safe foundation design, construction and performance without disturbing the environment;
vii) recommendations to ensure application of appropriate remedial measures for safe design, construction and performance of the buildings in the long term so as to reduce the incidence of geological disasters triggered by poor building construction practice.
Research Studies Carried Out into Problems Associated with Ground by the Division.
• Building on Compressible Soils.
Compressible soils have the tendency to exhibit differential settlements/movements which can cause distortions in structures and eventual collapse of buildings which can lead to disasters.
a) Avoid areas underlain by compressible soils.
b) Engineering geological expect advice is needed for site development on compressible soils.
Building on Waterlogged Areas.
These areas include old lagoon and dry stream channel.
a) Avoid building in such areas which can be liable to liquefaction during ground vibrations e.g. earthquakes.
b) Prior advice from engineering geological experts is needed before commencement of foundation construction.
• Building on Expansive Soils.
Seasonal wetting and drying of soils with smectitic minerals create foundation problems which include cracking of walls and eventual collapse of buildings and subsequent disasters.
a) Avoid building in such areas.
b) Development of such areas for housing needs expert advice.
• Building with Strained Silica
Failure of concrete structures may occur due to alkali- silica reaction effects when the silica is of volcanic origin or from fault zones.
Avoid building with aggregates containing silica of volcanic origin or from fault Zones.
Petrographic study report must be submitted prior to using the aggregate. When in doubt, always seek advice from a specialist.
• Building in Flood Prone and High Ground water Table Areas
Building in flood plains assumes ignorantly that the dried rivers may never be rejuvenated flood plains consist sometimes of inhomogeneous materials with variable bearing capacities and non- uniform settlement characteristics.
a) Avoid improving the site with FILL without prior advice from geotechnical experts;
b) Avoid adopting pile foundations in such areas without prior advice from geotechnical experts.
• Building on Expansive Soils
Seasonal wetting and drying of soils with smectitic minerals create foundation problems which involves cracking of walls and ultimate collapse of buildings.
Precautionary measures to be considered include:-
i) mechanical and chemical stabilization of the expansive foundation clay soils;
ii) moisture control;
iii) isolation of the foundation from potentially expansive clay soil;
iv) suppression of the swell pressure with structural loads;
v) thorough identification and geotechnical characterization of the Sub-soil system;
vi) determination of the depth of seasonal moisture variation associated with volumetric charges of the soil;
vii) location of the base of the foundation below the soil zone which is prone to volumetric charges with seasonal moisture variations.
a) Avoid building in such areas.
b) Developments of such areas for housing need expert advice.
• Building in Areas Susceptible to Mass movements
These include areas prone to landslides and rock- falls.
The geological history, discontinuity orientations, slope failure mechanisms, ground water conditions and material types invariably dictate the engineering design of building foundation hill areas (bottoms, slopes, tops).Effective interpretation of site conditions with respect to incipient or obvious instabilities in hilly/mountainous areas is of paramount importance prior to the development of the site. T he cost of remedial works after failure of a natural slope may be prohibitive. The following regulations must be observed to avoid loss of life and property.
a) Avoid building on steep slopes
b) Avoid building below scarps
c) Avoid building on colluvium
d) Engineering geological specialist advice is needed to build at such unstable and disastrous areas.
• Building on Erosive susceptible Soils and Rocks.
Progressive erosive phenomena on the surface and subsurface of a building site can produce hanging foundations and undercuts which later can cause ultimate collapse of buildings with subsequent loss of life and property.
i). Avoid areas which show signs of sheet, rill and gully erosion.
ii). Avoid areas with springs (these are centers for subsurface erosion and artesian
problems which lead to foundation failures.
iii). Seek expert advice before construction in such areas.
iv). Avoid building on friable rocks
v). Provide aprons to protect foundations on erosive susceptible rocks.
vi). Re-vegetate compound with vetiver grass to prevent further erosion
vii). Provide drainage gallery where and when appropriate.
In difficult situations, resort is made to expert advice from, for example, structural engineering and Architectural personnel.
• Building at Mining Areas
Mining areas are rife with abandoned or existing shafts, tunnels and wide excavations.
Groundwater loss through these mine shafts and tunnels causes depressions in the land surface without the application of dead or live loads. Swallow holes are also formed in the process giving way to land subsidence.
a. Avoid such areas for housing and industrial developments.
b. Engineering geological advice is needed prior to the development of areas with subsidence problems.
Technical Services Rendered in the Recent Past.
The major Geotechnical consultancy services executed by CSIR-BRRI are numerous. The list is quite long and it is not intended to call them out now. The long list speaks for itself that the Geotechnical Engineering Division has responded actively and positively to the Research-Commercialization activities in the Institute.
Current Stock of Geotechnical Engineering Equipment
The stock of Geotechnical equipment, secretarial and communication facilities are not the best. Arrangements are, however, under way to replace the obsolete equipment in the soil and rock testing laboratories. The soil investigations are carried out with the cable percussion drilling rig. Where clients request to enter the bedrock, we have no option but to hire the rotary drilling rig from sister institutes. This is not the best if we should go by the vision and objectives of the research/commercialization aspirations of the CSIR-BRRI.
Refereed journal papers in the Geotechnical Engineering Division have considered the following topics:
• Construction in tropical residual soils.
• Engineering properties of tropical residual soils
• The need to produce Site Investigation reports prior to construction of roads and buildings.
• Construction in expensive soils.
• A seismic designs and liquefaction potential of soils in the city of Accra and its environs.
• Remote sensing application to search for water resources and construction materials.
• Well engineered landfill sites.
• Susceptibility of ground to erosion to produce hanging foundations.
• Examination of slope design parameters and slope performance.
• Occurrence of mass movements in Ghana and appropriate preventive and remedial strategies.
• Hybrid materials for road construction.
Financing Research Projects and Contribution to the National Economy
Grants for research work and other related activities were not made available by the Government’s Ministry of Education, Sports and Science though the Division has been mandated to carry out research to sustain the Building and Road Construction industrial sector of the national economy.
The main research projects awaiting financing include:
i. Accra Earthquake Project
ii. Development of a New Lateritic Soil Material for Housing.
iii. Landslides and Erosion Control.
iv. Waste Management Problems
(i) Accra Earthquake Project
The project aims at assembling and analyzing geotechnical and seismic engineering data in order to establish a rational basis for land-use planning and engineering decisions for the establishment of settlements and infrastructure in the Accra area, which has a history of high seismicity. It also aims at setting out mitigating actions should any earthquake occur.
During the year, earthquake data were obtained form the Geological Survey Department in Accra for geotechnical micro zoning map to be produced.
The exercise, when implemented to fruition, would help to minimize planning, design, construction and maintenance costs of old and new developments in Accra. The project is faced with a major bottleneck, which is lack of funds. Arising from this, research activities to be carried out could not be accomplished. The objectives of the research activities include:
• data collection to ensure the widest dissemination of the results both in Ghana and globally within the scientific and engineering communities.
• identification of the distribution of faults, soils, rocks and other geotechnical factors which affect foundation design and stability in Accra.
These factors can enable the possible peak ground acceleration of earthquakes to be assessed and the whole of the Accra seismically micro-zoned.
(ii) Development of New lateritic Soil building Materials for Housing
The main objective of this project is the improvement of local laterite soils for the production of a durable building material for housing. The materials and methods involved have been selected so as to ensure cost effectiveness of the product and promote the use of local resources in the production. The project is actively being pursued even though there is inadequate fund for it. A prototype structure was constructed with the new material behind the domes at Fumesua for demonstration.
(iii) Landslides and Erosion Control
The project aims at studying landslides and erosion problems, with the view to establishing control measures to minimize their disruptive and damaging effects on property and economic activity. Areas visited to collect data include Bompata, Mampong-Jamasi road and Homuta.
iv. Waste Management Project
The project involves the geotechnical study of sites for the establishment of landfills and septic treatment facilities. Feasibility studies were carried out at Offinso and Kibi during the year.
v. Groundwater Resource Mapping and Pollution Protection
The project aims at locating potential groundwater sites in districts of Ashanti region for exploitation to meet rural water demands. Preliminary available geophysical data has been collected from all the 17 districts of the region for analysis
On-Going Research Activities
Slope Stability Studies
Landslide occurrence at Nyameadiso near Wansampobriampa in Akontombra District on Sefwi Wiawso – Aknotombra
Study of the Expansive and Engineering Characteristics of Soils in Kumasi,
Development of Hybrid Materials for the Construction of All-Weather Housing and Rural Roads.
Development of Technologies for the Construction of all Weather Dust-free Rural Roads in Ghana
Evaluation of Hybrid Soils for the Production of Quality Bricks.
Mapping of Groundwater Resource Using GIS and Integrated Geophysical Methods
Studies into Groundwater Pollution at Landfill sites
The Way Forward
The commercialization proposals by the CSIR include the following policies:
i. That most research and development activities should be demand driven.
ii. That all research and development operations should be cost effective
iii. That most of the research and development activities should lead to commercialization.
With these policies as the stage from which to operate, it is envisaged to embark on projects which are consultancy oriented. The essence of this move is to get the division operative in the absence of research grants. Arising from this the following projects would be pursued:
a. Ground investigations for civil engineering works using the cable and diamond drilling rigs.
b. Water bores at a fee for interested private and public institutions.
c. Search for quality materials (Burrow areas and quarries).
d. Any other geotechnically oriented services.
Involvement in Regional and National Organizations
1. National Disaster Management Committee
2. National Earthquake Mitigation Sub- Committee
Feature Photographs of Selected Field Activities in the Division
A. Cable Percussion, Rotary Drilling and In-situ Tests
Cable Percussion, Rotary Drilling and In Situ Testing operations are carried out in the field to obtain quality and reliable ground parameters for the design and construction of civil and mining engineering projects such as:
• Foundations for Simple and Multiple storey buildings,
• Highway and open pit slope stability analysis,
• Embankment, Tailings and Masonry Dams.
B. LABORATORY TESTING OF SOILS AND ROCKS
Determination of geotechnical parameters for the design of building foundations and other civil engineering works are also carried out in the Geotechnical Engineering Division. Determination of material quality for design and construction of highways, concrete works etc.
Geo – Physics