Geotechnical Investigation and Foundation Design
Report
Student Name:
ABC
Submitted To
XYZ
Date:
abc
Contents
Introduction: .................................................................................................................................... 3
Project Description: .................................................................................................................... 3
Address: ...................................................................................................................................... 3
Scope of the Design: ....................................................................................................................... 5
Site Investigation Report: ........................................................................................................... 5
Borehole log and corresponding subsurface profile: .................................................................. 5
Strata Plot:................................................................................................................................... 7
Sample Type:............................................................................................................................... 7
Recovery: .................................................................................................................................... 7
Borehole log and corresponding sub-surface condition: ................................................................ 8
Design Assumptions: ...................................................................................................................... 9
Design of Isolated Footing: ........................................................................................................... 10
Introduction:
Project Description:
The project is about the design of foundation for a residential building with three for the number
of stories.
1. 3 storeys
2. 5 storeys
3. 10 storeys
Each storey will be loaded with a dead load of 7.5Kpa and a live load of approximately 2.5Kpa.
The design foundation shall safely transfer safely the loading of the structure to the foundation.
The choice of the shallow footing depends on the designer whether combine or isolated but it
should not fail in bearing or excessive settlement.
The geotechnical report can be downloaded from the google scholar or any other database that
the designer may consider understandable and necessary. First we will prepare a borehole in
order to obtain necessary information for the necessary information for the design of footing.
Address:
The site is located at 2320 lester road Ontario Canada.
Figure 1 2320 SiteMap of the construction Area.
Figure 2 Schematic Survey Map of the area
Figure 3 Approximate Borehole location
Scope of the Design:
The work scope includes the design of the foundation only under three different scenarios. These
scenarios are discussed as under:
1. Design of foundation for three stories only.
2. Design of foundation for five stories residential building.
3. Design of foundation for ten stories residential building
Site Investigation Report:
The information pertaining to the soil, rock, or other materials, and their respective conditions as
stated in this report, has been derived from the observations made by the field-testing team at the
time of their work and at the specific locations where testing and sampling were conducted. The
classification and condition statements have been made in accordance with widely accepted
practices that are subjective in nature; therefore, it should be noted that no specific description can
be considered entirely accurate. Instead, they are indicative of the expected behavior of the
materials. It is important to note that the extrapolation of in situ conditions can only be made to a
limited extent beyond the test or sampling points. The degree to which such extrapolation can be
made is influenced by various factors, including the variability of the soil, rock, and groundwater
conditions, as well as the geological processes, construction activities, and site usage. Thus, it is
crucial to exercise caution and not rely solely on the information provided in this report when
making decisions related to the site in question.
Borehole log and corresponding subsurface profile:
The table below will describe common soil types and genesis.
Figure 4
the next table show terminology describing soil structure:
Figure 5
The classification of soil types are made on the basis of grain size and plasticity in accordance with
the unified soil classification system (USCS) (ASTM D 2487 or D 2488) which excludes particles
larger than 75mm. For particles larger than 75mm, and for defining percent clay fraction in
hydrometer results, definitions proposed by Canadian foundation engineering manual, 4th edition
are used. The USCS provides a group symbol (e.g., SM) and ground name (e.g. Silty sand) for
identification.
The standard terminology to describe cohesionless soils includes compactness as determined by
standard penetration test(SPT) N-value- also known as N-index. The SPT N-value is described
further as a relationship between compactness condition and N-value is shown in the following
table.
Figure 6
The standard terminology to describe cohesive soils includes the consistency, which is based on
undrained shear strength as measured by in situ vane tests, penetrometer tests, or unconfined
Figure 7
compression tests. Consistency may be crudely estimated from SPT N-value based on the
correlation shown in the following table.
Strata Plot:
Strata plots symbolize the soil or bedrock description. They are combinations of the following
basic symbols. The dimensions within the strata symbols are not indicative of the particle size,
layer thickness, etc.
Sample Type:
Figure 8
Recovery:
For soil samples, the recovery is recorded as the length of the soil sample recovered. For rock
core, recovery is defined as the total cumulative length of all core recovered in the core barrel
divided by the length drilled and is recorded as a percentage on a per run basis.
Borehole log and corresponding sub-surface condition:
As per the report a factored geotechnical resistance at ultimate limits states (ULS) and a
geotechnical reaction at serviceability limits states (SLS) of 150 KPa. The factored geotechnical
bearing resistance at ULS incorporates a resistance factor of 0.5. The geotechnical reactions at
SLS were developed consistent with a total settlement of 25mm.
Design Assumptions:
We derived that the bearing pressure of soil layer at which the foundation of the building will be
placed is 150Kpa with expected settlement of about 25mm. it is because 67% of the soil that
were tested is sand mostly in the top layers where we are expecting our foundation.
The design of a shallow foundation for a three-story building has been justified through the
following considerations:
Soil investigation:
A soil investigation was conducted at the site to determine the soil type, strength, and other
properties. Based on the results, a shallow foundation was deemed appropriate and designed
accordingly.
Building loads:
The loads imposed on the foundation by the building were calculated, including dead loads (the
weight of the building materials) and live loads (the weight of people and furniture). The
foundation was designed to safely support these loads within allowable limits.
Building codes and regulations:
The design of the shallow foundation was checked against the building codes and regulations
applicable to the project location to ensure compliance with relevant standards and safety
requirements.
Cost-effectiveness:
The shallow foundation design was found to be more cost-effective than other options available
for the site conditions, making it a viable and practical solution for the project.
Expert opinion:
Consultations were conducted with other professionals, including geotechnical engineers,
structural engineers, and architects, to ensure that the foundation design was appropriate for the
site and building requirements. Their input was incorporated into the design process to ensure a
comprehensive and optimal solution.
By considering and documenting these factors, the design team has provided a clear and
comprehensive justification for the use of a shallow foundation for the three-story building.
Design of Isolated Footing:
For the design of isolated footing first we have to find the reaction at the base of the column. For
that purpose we model the given problem in finite element based software ETABS and after
analysis we will obtain the reaction at the base of it.
Figure 10 A 3D view of the given model
Figure 9 Reaction obtained at the base of the building
As we can see from the figure the highest reaction is obtained location 3B and 3E a total demand
of 1938KN has to be accessed through the design of the isolated footing.
Now we will present some calculation for the design of footing under a total demand of 1938KN.
Given ultimate bearing resistance of soil = 150 Kpa.
Assuming a factor of safety of 2, the allowable bearing capacity of the soil is:
𝑞𝑎𝑙𝑙𝑜𝑤 =
150
= 75 𝐾𝑃𝐴
2
To determine the required footing area, we can divide the total load by the allowable bearing
capacity:
𝐴 =
1938
= 25.84 𝑚^2
(75 )
Assuming a square footing, the width of the footing can be calculated as:
𝑊 = 𝑠𝑞𝑟𝑡(𝐴) = 𝑠𝑞𝑟𝑡(25.84 𝑚2 ) = 5.08 𝑚
Therefore, a square footing with a width of 6 meters is required to support a total load of
1938KN on soil with a bearing capacity of 150KPA and a factor of safety of 2.
To find the thickness of the foundation we have.
𝑀 = 0.134 𝑓𝑐𝑘 𝑏𝑑𝑤
Here M = demand moment on the footing = 998 KN-m (from analysis)
B = width of the footing = 6m = 6000mm
𝐹𝑐𝑘 = 25𝑁/𝑚𝑚2 (Characteristic concrete strength)
𝑑𝑤 = 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑑𝑒𝑝𝑡ℎ 𝑜𝑓 𝑓𝑜𝑜𝑖𝑡𝑛𝑔
Putting the values, we get
𝑑𝑤 = 222.86𝑚𝑚
Next, we will present an overall drawing that will show the plan and arrangement of footing.
Figure 12 image showing the foundation of the building
Figure 11 Foundation Typical section showing it's depth below Ground