Reference no: EM132901964 , Length: 15 pages
SEV200 Geotechnical investigation and Design
Design project
The aim of this assessment is to help you further develop and demonstrate the following skills:
• Applying soil mechanics principles and theories to analyse stresses and deformations
• Self management and addressing feedback
• Critical thinking at different stages of analysis, design, and communication of results
• Problem solving through proposing a foundation design
• Report writing and visualisation
Requirements
You are required to analyse the proposed initial footing designs and propose an improved footing design for these structures. The main constraints for this design practice are listed in Section 3.2.
It should be noted that this practice is a very simplified and incomplete version of a real foundation design project. As you will later see in SEV362 - Geotechnical Engineering, in large projects where you have to calculate the bearing capacity of the soil, the bearing capacity is not independent of the foundation size.
You have to complete the following requirements in this project:
1. Calculate the foundation pressure under the four footings used in ID1 and ID2 (see Section 3.1)
2. Propose an improved foundation design (see Section 3.2)
3. Compare the two initial designs with each other and with your proposed improved design and substantiate through calculations and discussions why your proposed design is better (see Section 3.2)
4. Provide a geological cross section of the site (see Section 3.3) 5.Calculate the settlements (see Section 3.4)
6.Respond to feedback and self-reflection (see Section 3.5) 7.Write the final report (see Section 3.6)
Pressure under footings
As the first step in this project, you need to calculate the pressure distribution (foundation pressure) under the four different footings (F1 to F4) used in the two initial footing designs shown in Figs. 6 and 7, due to the given column loads in Fig. 4, Table 1, and Fig. 5.
This part basically involves only statics calculations. To calculate the foundation pressures, you need to:
1. find the centroids of the given footing
2. find the resultant forces and moments at this centroid due to relevant column (and wall) loads
3. calculate the pressure distribution based on the resultant forces Dedicated studio sessions are scheduled to help you complete this task.
Many other calculations in this project depend on the results of this task. You have the chance to submit your calculations of this part as a separate submission under the title of Design project - Interim and receive feedback to correct possible mistakes for your final report. For further information, see Sections 3.5, 4, and the rubric for this assessment task.
Proposing an improved design
Engineering design is generally an iterative process: you start with an initial design, analyse it, then improve it based on analysis results and other design constraints and requirements. In this process you need to know what are the required constraints and also how to compare two designs with each other, or in other words, knowing what are the design objectives. These are explained in two separate subsections below.
Design constraints
There are few important design requirements that have to be satisfied :
1. You have to use only spread footings. Deep foundations (e.g. piles) are not allowed in this project.
2. The foundation pressure should not exceed the nominal bearing capacity of the soil which is 125 kPa.
3. The footings cannot go beyond the given site boundaries.
4. Separate footings should have the minimum distance of 0 .5 m from each other. If other requirements force you to have smaller distances, you have to merge the close footings into one footing.
5. The centre of all columns should have a minimum distance of 0 .25 m from the footing edges in all directions.
You can easily and quickly verify that constraints 1, 3, 4, and 5 are satisfied by both of the initial designs, ID1 and ID2 in Figs. 6 and 7. You will be able to verify the constraint 2 for these initial designs after completing the task in Section 3.1.
Design objectives
In this project, you can compare different designs based on the following objectives: 1.Near uniform foundation pressure distribution:
Ideally a good footing design will cause a near uniform pressure distribution on the foundation. This ensures that the footing design is optimised in terms of area and hence material and footprint. To be able to systematically improve the foundation pressure, it is necessary to calculate the centre of pressure for each group of columns which are to be placed on a single footing.
2. Minimum disturbance on natural site features:
As noted before, in this project it is preferred that the natural topography of the site is kept intact as much as possible. Note that this is not similar to minimising earthwork. Rather you have to attempt to place your footings so that the existing topography is affected the least. Considering the given position of columns and the topography map as shown together in Fig. 8, this would basically mean keeping the two hilly sides on lower right and upper left as least disturbed as possible.
3. Any other reasonable objective:
Geological cross section
Borelogs information is provided in Section 2.1. You need to combine these borelogs and prepare a 2-dimensional cross section of the ground based on these borelogs showing the soil layers and their thickness across the project site. You also need to very briefly describe the profile your obtained and provide few comments on the assumptions you used in this process.
You have to calculate the total settlement under your proposed design. The total settlement is the sum of elastic (immediate) and primary consolidation settlement. Secondary consolidation settlement is not required in this project.
You mainly need to calculate the settlements under your own proposed design. However, by calculating settlements under the initial designs and comparing them with settlements under your proposed design you can compare the two designs in this aspect as well which can improve your mark as indicated in the "improved design and supporting discussion" section in the rubric. Settlement calculations depend on the foundation pressure (Section 3.1) and also the soil profile in your geological cross section (Section 3.3). The required soil properties for elastic settlement calculation are provided in Section 3.
For consolidation settlement calculation, apart from basic soil properties given in borelogs, raw oedometer test results are provided as an Excel file on the unit website (follow this link). Also see Appendix A. From oedometer results you can calculate the necessary parameters you need in calculation of consolidation settlement. You can also use computer programs like Excel or Matlab to plot the necessary graphs instead of hand plotting.
As will be discussed in one of the classes, for nearby buildings, consolidation settlement also depends on the order of construction. For your proposed design, you need to discuss the effect of construction order on the consolidation settlement of different footings if your design involves more than one footing. This discussion should be based on required calculations.
See the associated rubric for details about the required outputs for this task. There will be a couple of studios dedicated to help you with this task towards the end of the trimester.
Report
You need to compile your results and outcomes in form of a technical report. In your report you should have the following sections:
1. Soil properties: here you would provide your cross section, and summarise the properties of the soil profile based on given soil properties, and your analysis of raw test results. See Section 3.3
2. Analysis of the initial foundation designs: see Section 3.1.
3.Proposed design and comparison: see Section 3.2.
4. Settlement calculations: see Section 3.4.
5. Response to feedback and self-reflection: see Section 3.5.
You can break the above sections into subsections if necessary. You can also add sections if needed.
Your report should be professionally written and organised, with correct citation and cross referencing style. You should also respect the page limit stated in the unit guide, i.e. maximum 15 A4 pages including figures, tables, and appendices. The cover page is not included in the page limit.
The minimum formatting requirements for this report are as follows:
1. The report should be typed on A4.
2. Cover page with your name and student ID.
3. Table of content (this can be included on the cover page like this document).
4.Pages should be numbered.
5.Margins should be reasonable, i.e. not smaller than 1 cm or larger than 5 cm on any side.
6.Figures and tables should be numbered and have captions. For figures, captions should be placed below them, and for tables, captions should be placed above them. There shouldn't be a page break between a Table or Figure and its caption.
7.Sections and subsections should be numbered.
Attachment:- Design project.rar