Site Investigation - Assignment

7. NEW ADVANCES IN SITE
INVESTIGATIONS AND IN-SITU TESTING
AND MONITORING

TABLE OF CONTENTS
INTRODUCTION...........................................................................................................................1
SITE INVESTIGATION AND BRIEF INTRODUCTION TO THE ADVANCEMENTS ..........1
IN- SITU APPROACH FOR MONITORING AND TESTING OF THE FIELD .........................2
TECHNIQUES FOR TESTING AND INVESTIGATING SITES VIA IN- SITU APPROACH .3
1. Standard penetration method (SPT)........................................................................................3
2. Cone penetration testing (CPT)...............................................................................................5
3. Field vane shear testing method..............................................................................................8
4. Dilatometer testing (DMT) procedure ...................................................................................9
5. Full flow penetrometers testing method ...............................................................................11
In-situ testing case study of peat ...................................................................................................12
Case study of site in the Bursa city of Turkey...............................................................................18
CONCLUSION .............................................................................................................................21
REFERENCES .............................................................................................................................22

INTRODUCTION
Site investigation is known as the process of gathering information and data related to a
field. This investigation is useful to analyse hazards which may exist beneath inspection site. It
gives attributes for foundation and development of infrastructure (Sitharam, Vipin and James,
2018). The report will highlight the advancements of site investigation techniques. The rapidly
changing technologies in development and innovations have given rise to variety of methods for
monitoring and testing these sites.
One of the most commonly testing methods which are used for investigating site is in-
situ testing in which instruments are placed in borehole at specific precise location for
examination of field (Look, 2014). Thus, these methods are helpful in explaining behavioural
and engineering characteristics of ground. The document will analyse various advanced
techniques of in-situ monitoring which are used widely. It will also focus on few of these
methods by explaining their implementation through a case study.
SITE INVESTIGATION AND BRIEF INTRODUCTION TO THE
ADVANCEMENTS
Site investigation provides an important assessment of properties related to rocks and soil
found beneath any field. This evaluation also describes how these attributes establish an
interaction with the surrounding development. Such research related to site helps geologists to
develop an awareness regarding hydrological and geological threats which can cause damage to
living beings, environment as well as property (Cox and Mayne, 2015.).
Site investigation involves the following stages:
 Firstly, it is required to have well defined objectives for accomplishing investigation. It
also includes analysis of various requirements and scope of research.
 It is also requisite to review historical facts related to field as well as geological concept
related to the site. This desk study helps in conducting testing with more efficiency.
 In the next stage of site investigation, design for the purpose is identified along with
potential and real hazards which may be present. This stage is called site reconnaissance.
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 After reconnaissance, major investigation is carried out by using different techniques
such as collecting intrusive or non-intrusive samples so that they can be tested and soil
parameters can be determined.
This investigation provides details of characteristics like susceptibility to water levels and their
flow, properties related to hydro-geological behaviour, accumulation of gases, hazard
identification and soil characteristics of the field. The site investigation methods have observed
significant advancements in procedures. Data measurement and acquisition trends are greatly
affected and led to multisensory devices. Tools such as seismic and triple piezocone cone are
evolved with less complexity so that they can be used in routine basis (Hunt and et.al., 2016).
The most effective and significant advancement is the exploration of sites with the help of in-
situ tools.
IN- SITU APPROACH FOR MONITORING AND TESTING OF THE
FIELD
In- situ testing methods are used to evaluate physical characteristics of site. Some tracts
which consist of good quality of soil or clay like material can provide samples easily. And the
assessment of these samples via testing can evaluate soil characteristics and rock configuration.
But for the sites where it is difficult to obtain sample and apply testing methodologies, in- situ
approach can be used. The sites which are characterised by clay, gravels, soil comprising stones
or fractured rocks are recommended to use in- situ methods.
This approach is used to analyse penetration resistance, permeability, strength and
compressibility features of the site. In- situ investigation methods involve variety of techniques.
The selection of any particular technique depends upon purpose of site examination. The in- situ
method of investigation is required to obtain statistics related to ground water. It also gives
option to install instruments which can monitor the stages of investigation so that lean processes
can also be implemented for designing or construction purpose.
In this approach, boreholes and pits are used to install monitoring and testing equipment
so that soil permeability, measurement of flow rate of fluids and soakaway design can be carried
out (Wang and et.al., 2015). For site investigation, the main purpose is to carry out
environmental research for in- situ methods that monitors emission of gases within site and
presence of contamination causing factors.
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TECHNIQUES FOR TESTING AND INVESTIGATING SITES VIA IN-
SITU APPROACH
For evaluating the site characteristics, the following advance techniques can be used:
1. Standard penetration method (SPT)
It involves split spoon as a sampler in borehole for finding site characteristics. The
sampler is provided with coupling, barrel and driving shoe. The split barrel is provided with two
parts. In this testing approach, the sample tube is inserted into site at bottom of auger hole. The
insertion is achieved by generating blows from a slide hammer. In order to draw result tube is
penetrated into ground up to 150 mm. Up to 450 mm, number of blows which are used by
sampling tube for penetrating each 150 mm are recorded (Lunne, Powell and Robertson, 2014).
The measurement of joint number of blows for second and third penetration is known as the
standard penetration resistance. It is also abbreviated as N value.
The number of blows are used to provide an idea of the ground density. The iterations of
standard penetration test are executed at regular intervals of 0.75 m within borehole. The
intervals can be increased but then it will require enhancement of depth of the hole. For the sites,
which are accumulated with boulders the N value of SPT is measured for distance of initial 300
mm.
Corrections for N value of SPT
The data and records obtained from these testing stages can be used for only liquefaction
analysis. To apply it for further investigation, seismic bore logarithm is found by applying
corrections to N value. The seismic log for borehole gives details regarding depth, soil density
and stress measurement, correction factors and the rectified N value. The measured N value
which is obtained from the test procedures require validation and correction in aspects such as
overburden pressure, diameter of borehole, length of rod and the energy of hammer (McGann
and et.al., 2015). The N value is increased as overburden pressure rises. Thus, this correction is
required to give valid results. The corrected burden pressure is given by the following equation:
Cn = 2.2 / (1.2 + effective overburden pressure / 100 kPa)
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The final corrected N value is given by the multiplication of each of corrected N value in terms
of above mentioned correction factors.
Factors affecting results and measurements
The properties of drilling liquid which is used in borehole also influence the results of
test. Frequency of hammer blow, borehole diameter and sampler configuration are also critical
factor which affects accuracy and efficiency of technique. Thus, stabilisation and drilling
procedure of borehole cannot be considered for granted. They require great concentration and
careful approach. Penetration resistance is given by the formula:
Penetration resistance = Calculated N value = (Number of blows / 0.3 m)
There is a correction between resistance and granular soil density. For instance, SPT N
value of more than 30 demonstrates that the higher density is also higher (More than 65). On the
other hand, N value between 0 to 4 describes very loose correlation with density of only less than
15 (Tarawneh, 2017).
The testing procedure also considers energy efficiency. Various types of hammers that
can be utilized to drop. For instance, Donut hammer, automatic trip hammer and safety hammer
can be used. Each type has different range of correction after measurement. The dropping
hammer transfers energy to sampler. Thus, energy ratio is also critical parameter which
influences N value and ultimate results of testing technique.
Error probabilities in SPT
In case, if hole is not cleaned properly then it can increase the value of SPT-N. Inaccurate
hammer weight and its careless drop can vary energy generated due repetitive strike of hammer
Due to the variation in hammer energy errors in N value can increase. During testing when bent
drill rods are used then it inhibits the transfer of sampler energy. This inhibited energy movement
increases N value. Ungreased sheaves of hammer can cause free falling of hammer. So reduced
hammer energy can also give increment in SPT-N observation. In site investigation, there are
cases when water level in borehole in not maintained or meet the desired head. Thus, in such
instances, soil may get rinsed and bottom of hole also becomes quick. The accumulation of these
incidents is responsible to decrease the N value than the actual reading.
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