Geotechnics & Soil Mechanics 1: Detailed Analysis of Rocks and Soils

This document presents a comprehensive solution to a Geotechnics and Soil Mechanics assignment, covering various aspects of rock and soil analysis. It begins with an overview of rock classifications (igneous, sedimentary, and metamorphic) and their applications in construction. The assignment delves into the Bowen reaction series, explaining the formation and weathering characteristics of igneous rocks. It further explores the use of different rock types in various construction scenarios, such as foundations, facings, and aggregates. The document also addresses the use of soil as a building material and discusses soil sampling, including brownfield site assessments, and the differences between disturbed and undisturbed soil samples. It covers soil classification methods based on grain size, texture, and plasticity, and explains the determination of soil plasticity using the plasticity index and liquid limit. In-situ and laboratory testing methods, including vane shear testing, oedometer tests, and CBR tests, are explained. The document also details the calculation of soil properties such as moisture content, bulk density, and specific gravity. Finally, the assignment provides references to relevant books and journals.

GEOTECHNICS & SOIL
MECHANICS
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TAKS 1
(a)
There are three main classes of rocks:
Igneous rock: These types of rocks are formed through cooling and solidification of magma
which is also known as magma (Stoops, Marcelino and Mees, 2018).
 Sedimentary rock: These types of rocks are formed when sediments are deposited out of ice,
air, gravity, wind or water flows carrying various particles in suspension.
 Metamorphic rock: These types of rocks are formed by chemical and physical alteration of
pressure and heat of existing sedimentary or igneous material into their denser form.
(b)
Igneous rock
 Granite: It is used in architectural construction, monuments.
 Pumice: It is used as an additive in cements or for plaster like concrete.
 Gabbro: It is used as a crushed stone for road metal, railroad ballast.
 Basalt: it is mostly used as an aggregate in construction projects.
Sedimentary rock
 Coal: It is mainly used in powerplant in order to make electricity.
 Shale: it is used to make bricks or any other construction material such as cement.
 Conglomerate: it is mainly used to as a fill material for roads and construction.
 Sandstone: Used in pre historic construction and was popular in ancient time building
materials.
Metamorphic rock
 Schist: In construction it is used as a building stone or decorative stone.
 Gneiss: In construction it is used for flooring, facing stones etc.
 Quartzite: In construction it is used as decorative stone for cover walls etc.
 Marble: In construction it is also used as building stones (Borrelli and et.al., 2016).
(c)
Bowen Series of rock classification is also known as Bowen reaction series. It helps in
describing way in which magma minerals changes when they cool down. It helps in
classification of igneous rocks (Zagórski and Kisiel, 2018). It can help in explaining weathering
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characteristics of igneous rock. It helps in explaining the way in which magma minerals changes
when they cool down.
Figure 1 Bowen reaction series
(d)
i) As foundations for roads: Stones used in this situation are required to have high abrasive
resistance, should be uniform and composition.
ii) As facings for structures: For this mostly sedimentary rock are used whose strength and
stiffness reduces slowly. Strengths and weakens of these kinds of rocks can be conforming
pressure on them.
iii) As aggregate for concrete: stones used in this situation should be highly durable, strength of
these stones should be high
iv) As building stone: Rocks used in building stones should have high compressive strength,
transverse strength should also be high and porosity should be low.
(e)
Soil is used for building materials like bricks, cement. Other than this it can also be used
for building materials such as wood boards, insulation fibres (Chertov and Nadporozhskaya,
2018). Many times, soils are caked and dried to make bricks. Alternative that can be used instead
of soil are granular filters, rockfill materials etc.
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(f)
Strength of 20% material taken out of quarry have average comparative strength and as the
value of these materials increases strengths of these materials also increases whereas strength of
rock masses a be determined by identifying discontinuities in rock masses.
(g)
RQD is a kind of measure through which degree of jointing in rock masses is measured as
drill core in length percentage (Monged, Hussein and Khater, 2018). In other words, it is used to
measure the overall quality of rock masses. It is used to evaluate deformation of modulus and
compressive strength or rock. If rock masses is rough then it helps in measuring degree of
fractures in rock. It also helps in measuring quality of RQD i.e. high-quality rocks has more
RQD whereas low quality has low.
TAKS 2
(a)
Brownfield sites are previously developed lands that are not used currently irrespective of
the fact that they are contaminated or not. These are normally abandoned areas of towns or cities
that have either been used for commercial purposes or industrial purposes previously (Bloise and
et.al., 2016). These types of sites are completely different from other types of sites such as
greenfield sites as other sites are undeveloped and can be used for agriculture also other than
construction whereas Brownfield sites can only be used for construction.
(b)
 Ground survey in a brownfield site: in this ground risk is calculated so that risk and
unexpected cost related to that site can be calculated. For these sites mostly construction
surveys are only done.
 Ground survey in other site: Other sites all other kinds of ground surveys can be done such as
boundary survey, topographic surveys, construction survey, bathymetric or
Hydrographic surveys can be done (Kassai and Sisák, 2018).
(c)
Distributed Soil sample Undistributed soil sample
 Stress condition changes
 There is change in void ration and water
 Due to disturbance in soil structure there is
no change in soil condition
 No change in void ration and water content
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content
 Chemical changes are found in this  No changes in chemical properties.
(d)
Laboratory test that can only be done on undistributed samples CBR or unconfined com-
pression tests. These are used to test moisture to the desired dry density in special cylindrical
moulds (Vrščaj and Kralj, 2017). Other than this compressibility or strength testing is done only
in undistributed testing. Geology age testing of undistributed soil is also done only in this type of
soil
(e)
Soils are broadly classified under various categories but mainly used classification are:
 Based on grain size: in this on the basis of grain size or particle size soil is classified. Under
this classification nature of the soil type cannot be defined.
 Textural classification: in this Classification of soil is done on the basis of particle size and
their percentage of distribution. As per this classification name of soil depends upon
percentage of sand, clay and silt.
 Unified soil classification: in this classification is done on the basis of plasticity
characteristics of soil and grain size.
(f)
Soil Plasticity is determined from plasticity index and liquid limit. Each type of sol sample
is plotted on modern plasticity chart and according to this chart soil are classified as per their
representation point (Zinck, 2016). So, it can be said that in order to classify soil on the basis of
plasticity it is required to conduct a test on soil sample.
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Figure 2 Plasticity chart and soil classification
(g)
Sampling of soil in situ is used for investigating soil where an instrument is placed in
borehole to measure situ characteristics of a soil or a rock. Sample of soils in situ used for testing
bulk density depends upon soil texture. It is important to investigate type of soil texture so that
bulk density can be measured (Espinosa, Moreno and Bernal, 2018). There are two methods to
investigate bulk density of soil sample: core method which is used to test cores fragments that
occupy less than 25% by volume and second is excavation method used for gravelly soil. Sher
strength of undistributed soil can be measured by measuring the overall strength of natural soil.
(h)
Merits of in-situ testing are:
 this type of test is carried out in natural environment which can help in determining
modification and effects to strains, stress, particle arrangements.
 Helps in detection of planes of weakness, defects are more likely and practical
Merits of laboratory testing are:
 While testing, testing environment is in control so that intensity level can be controlled.
 Provides proper relative density and strength of the soil sample (Grove and Brown, 2018).
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(i)
Soil samples should be taken to a depth of 2 meters, so each soil horizon is tested till a
certain depth. If water depth is found in depth which is less than 2 meters then soil samples are
taken as deep as possible.
Too little soil samples can lead to unwanted results or extremely high soil test results. It is
dangerous because it can lead to wrong or false results whereas too deep soil sample can disturb
the test results above expectations and might overestimate the soil nutrients.
TAKS 3
(a)
 soil moisture content: it can be calculated by subtracting weight of dry soil from moist soil
and by dividing weight of dry soil
 bulk density: it can be calculated using three methods mechanical core sampler, acoustic
sensor and nuclear radiation sensor (Fichter and Whitmeyer, 2019).
 specific gravity: for this ratio of volume of sample at standard temperature and weight in air
of same volume of distilled water at same temperature.
(b)
Method of measuring shear strength in-situ is known as vane shear testing. It is used to test
undrained shear strength of the soil. Method used in laboratory to measure shear strength is Vane
Shear Test. However, this test has some limitations with respect to type of soil used for testing
like it is not suitable for fissured clay type soil or soil that contain sand or slit lamination as these
types of sands won’t give accurate results.
(c)
Soil compressibility in laboratory is measured using oedometer or consolido-meter (Ma
and et.al., 2017). For using this device for measurement of soil compressibility time plays a vital
role as in this time to time, time deflation plots are measured. If the soil is kept for longer
duration of time then thickness soil deposition increases.
(d)
It is a measurement of material resistance to penetration of standard plunger under
controlled density and moisture conditions (Prothero, 2017). Some principles behind CBT testing
are: Ph of soil depends upon difference in Soil and water ratio, extractable P increases with
decreasing soil: water ration.
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(e)
Liquid limit test: in order to perform this test in laboratory following things are used: cup, flat
grooving test, liquid limit device, ground glass plate, gage and cam. And while conducting the
test following things are calculated: Mass of empty container, ass of container + wet soil, mass of
container + dry soil and Water content and based on this liquid limit is calculated and a graph is
plotted (Lin, 2016).
 Plastic limit test: in order to perform this test in laboratory following things are used: cup,
flat grooving test, liquid limit device, ground glass plate, gage and cam. After testing plastic
limit and plasticity index is calculated and a graph is plotted for appropriate measurement of
results.
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REFERENCES
Books and Journals
Bloise, A. and et.al., 2016. Naturally occurring asbestos (NOA) in rock and soil and relation with
human activities: the monitoring example of selected sites in Calabria (southern
Italy). Italian Journal of Geosciences. 135(2). pp.268-279.
Borrelli, L and et.al., 2016. Weathering grade in granitoid rocks: the San Giovanni in Fiore area
(Calabria, Italy). Journal of Maps. 12(2). pp.260-275.
Chertov, O.G. and Nadporozhskaya, M.A., 2018. Humus Forms in Forest Soils: Concepts and
Classifications. Eurasian soil science. 51(10). pp.1142-1153.
Espinosa, J., Moreno, J. and Bernal, G. eds., 2018. The Soils of Ecuador. Springer.
Fichter, L.S. and Whitmeyer, S.J., 2019. No Rock Is Accidental! Stratigraphy, Structure, and
Tectonics in the Wilson Cycle. In Developments in Structural Geology and
Tectonics (Vol. 5, pp. 145-160). Elsevier.
Grove, T.L. and Brown, S.M., 2018. Magmatic processes leading to compositional diversity in
igneous rocks: Bowen (1928) revisited. American Journal of Science. 318(1). pp.1-28.
Kassai, P. and Sisák, I., 2018. The role of geology in the spatial prediction of soil properties in
the watershed of Lake Balaton, Hungary. Geologia Croatica. 71(1). pp.29-39.
Lin, N., 2016. Petrochemical characters of the igneous rocks exposed in the Momeik-Myitson
area, Momeik Township, Northern Shan State.
Ma, H. and et.al., 2017. Compositions, Proportions, and Equilibrium Temperature of Coexisting
Two‐feldspar in Crystalline Rocks. Acta Geologica Sinica‐English Edition. 91(3).
pp.875-881.
Monged, M.H., Hussein, M.T. and Khater, A.E., 2018. Elemental and radiological aspects of
geothermal springs and nearby soil and sediment of Al-Lith area: concentration and risk
assessment. Environmental earth sciences. 77(12). p.427.
Prothero, D.R., 2017. BUILDING BLOCKS: MINERALS AND ROCKS. In California's
Amazing Geology (pp. 23-44). CRC Press.
Stoops, G., Marcelino, V. and Mees, F. eds., 2018. Interpretation of micromorphological
features of soils and regoliths. Elsevier.
Vrščaj, B. and Kralj, T., 2017. Slovenian soil classification and WRB. In The Soils of
Slovenia (pp. 61-75). Springer, Dordrecht.
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Zagórski, Z. and Kisiel, M., 2018. Forms of iron in parent rocks of soils developed from Lower
Triassic (Buntsandstein) deposits in the NE part of the Holy Cross Mountains
(Poland). Soil Science Annual. 69(4). pp.259-271.
Zinck, J.A., 2016. The Geomorphic Landscape: Classification of Geoforms. In Geopedology (pp.
101-125). Springer, Cham.
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