48360

Geotechnical Engineering

Design Project

DESIGN PROJECT

INTRODUCTION

It is important to note that this design project is a group task, with each group comprised of two members.

A company is planning to undertake a construction project on land formerly used as a storage area for a petrochemical factory. You have been tasked with assessing certain geotechnical aspects of this project.

This project presents an open-ended problem-solving challenge, necessitating the application of proper engineering assumptions based on common sense, engineering principles, and some research.

PROJECT DESCRIPTION

The development involves the construction of three retaining structures (north, east and west), an earth batter wall (south), a proposed building, a proposed car park and a steel water tank.

The project in particular consists of construction of:

· A concrete walled industrial building with plan dimensions of 16 m × 40 m. The building is to have an on-ground concrete floor slab 120 mm thick, with a finished RL of 13.80 m. The walls are load bearing and there are some internal columns carrying the weight of the roof and other elements.

· A steel water tank having an external diameter of 12 m and an effective height of 8.5m, with its base at RL 18 m (top of the circular concrete footing). 

· The weight of a large water tank (made of metal) could be around 1.5% to 3% of the weight of water inside the tank (i.e. total water capacity).

· The weight of the circular concrete footing would be around 5% to 8% of the weight of water in the tank with its full capacity.

· Pressure of water can be calculated based on the height of water in the tank. The water pressures factor for stability analysis is equal to one. The pressure due the weight of the empty tank plus its circular foundation would be between 8 kPa and 12 kPa.

· Other assumptions are welcome and can be accepted with simple justifications.

· There is an existing one-storey double brick building on the site. The RL of the slab on the ground is 17.6 m (top of the slab).

A “Site Plan” is attached, showing the location of the tank, the car park (RL 17.5 m, finished surfacing) the proposed and existing buildings. The southern area of this site will act as the access point during construction. This access point will permit vehicle, machinery and temporary pedestrian access, as well as the delivery of tools, equipment and construction supplies. As a result, this area will undergo change at multiple stages of the project, and the landscape will not reach its final state until the project approaches completion. To create a homogeneous earth structure and ensure confidence in the batter design, only one of the sand types found on site will be used to reconstruct the earth batter. The light brown sand located in the fourth layer of this site has been selected because it is readily available. A sufficient quantity of this sand will have to be stored on site during the bulk excavation of the lower level, prior to reconstruction the sand stockpile will have to be conditioned and hydrated to ensure that 95% of standard compaction can be achieved.  

The structural engineer for the project has determined the proposed building loads and they are as follows:

· Wall vertical loading per meter run (including the weight of foundation): 150 kN/m

· Wall moment per meter run (towards inside the building): 70 kN m

· Total load of each column (including the weight of foundation): 180 kN 

In addition, 3 boreholes have been sunk at the locations shown on the Site Plan and the logs of these boreholes are included in this brief.

REQUIRED TASKS TO BE CUNDUCTED

You are required to prepare a brief report to address the following aspects:

1. Find the consistency of the soil layers based on SPT N-values and provide a cross section of the ground layers of the site based on the information given in 3 borehole logs, which are attached in this document. Clearly show the bedrock and groundwater level positions.  (5%)

2. Based on the AS 4678 requirements, provide geotechnical design aspects of an anchored retaining wall that should be employed between the proposed building and the water tank. This should include sufficient results to enable the structural engineer to design the wall section, including the embedment depth, the minimum free length of the anchors, the anchor tensile force (assume the anchors spacing is 2 m) and the maximum moment of the wall per metre run that can be induced in the retaining structure. Assume position of the anchor is 1.8 m below the ground surface and the angle of the anchor is 15 degrees. (15%)

3. Design the width of the wall foundation (only a typical strip footing), the column footings (only a typical square footing) and the diameter of the water tank circular foundation. (15%)

4. Estimate settlements of the wall, column and water tank footings. Assume the average drained Poisson’s ratio of the soil is 0.30 and use the following formula to calculate the soils drained Young’s modulus in kPa: E_s = 800 (N+13). (15%)

5. Using the method of slices, analyse the slope stability for the site south access batter and find the design slope angle to satisfy the required factor of safety of 1.6 ± 0.05.

Assume the height of slope is H1 = 3.6 m and the heigh of bottom sand layer is H2 = 5 m as shown in the figure. Appy a minimum surcharge of 5 kPa. Assume water depth is 5.5 m from the top of the slope. Solve this question for two different scenarios.  

Scenario 1 (use compacted sand for top layer): Assume the effective friction angle of stabilised soil is 32°, the total unit weight of soil is 19 kN/m³ and the effective cohesion of the stabilised soil is 1 kPa.

Scenario 2 (use cement stabilised sand for top layer): Assume the effective friction angle of stabilised soil is 36°, the total unit weight of soil is 20 kN/m³ and the effective cohesion of the stabilised soil is 8 kPa.

Bottom sand layer: Assume the effective friction angle of sand is 30°, the total unit weight of soil is 18 kN/m³ and the effective cohesion of the stabilised soil is 1 kPa.

You need to copy and paste at least 4 trials for each scenario to find the desired angle. (20%)

Guidelines:

You can use : Free Online Slope Stability Analysis for factor of safety.

https://calcforge.com/1/2/free-slope-stability-calculator

Or use Slope/W a module of Geo-Studio software and apply Morgenstern-Price or Spencer limit equilibrium method.

6. Employ three generative AI tools, including ChatGPT, Google Gemini, and Microsoft Copilot to find the answers to following questions, separately. You need to ask powerful follow-up questions from these generative AIs to enhance the answers. Please copy and paste your prompts and the GenAI responses for each AI tool. Then provide a reflective report (not more than one page) based on the generated responses and compare them with you own answers based on materials provided in this subject. (20%)

· Outline the recommended sequence of construction activities for this site.

· Provide a detailed list of recommendations for any additional field soil exploration necessary to finalize the design. Be specific; for instance, if additional boreholes are required, indicate the suggested quantity, precise locations, and recommended depths.

· List the essential laboratory tests needed and explain the purpose of each, specifying how they contribute to the design process.

The report should comprehensively address all the above aspects, including the associated workings and detailed calculations. The report must include a Title Page, Executive Summary of the main findings, Table of Contents, Project Scope, Detailed Calculations, and Results for all six outlined sections, along with a References list. Ensure all figures and tables are properly numbered and titled. If any figures or tables are sourced from external references, please provide appropriate citations or acknowledgments. (10%)

Note: The design of car park foundation and pavement, the design of retaining wall between the proposed building and the existing building, the design of retaining wall between the proposed building and the proposed car park, and landscape design are excluded in this design project.  

SUBMISSION

Submission date for your report is given in Canvas.

Each group will prepare only one report and one MS-Excel file, writing the names of both team members. However, each team member should individually submit that report.  

The Report as a pdf file and Calculations as an Excel file should be submitted via Canvas link.