Project 1: Geotechnical investigation for highway construction
Project 1: Geotechnical investigation for highway construction
Project No. 1-6
Learning objectives: This activity will provide students with opportunities to a) develop critical skills necessary to correctly interpret and analyze field and laboratory data, b) experience what geotechnical engineering is like, and c) develop problem-solving skills.
Due date: September 16 (week 8), by 11.59 pm.
Submission: Online submission.
Weight: 25%.
Feedback: Feedback and mark will be given to students approximately within 2 weeks following submission.
Introduction
A detailed geotechnical investigation was conducted by Geotechnique Partners International Pty Ltd to study subsurface conditions of the proposed area. This report presents results of field and laboratory investigation including a map of the area, borehole logs and data from laboratory examination of soil samples. You are required to interpret and analyse the obtained data, estimate stresses acting in soil mass, identify geotechnical issues that can occur during construction, and investigate the compaction characteristics of borrow sand which will be used to construct road embankment.
This document contains:
- Field and laboratory data;- Task description;- Report form;- Marking criteria.
Figure 1. Map of the project area
Figure 2: Borehole BH10, Elevation 1.18 m.
Borehole log legend: Drilling method: W-washbore, T-TC bit. Sample type: U50-undisturbed sample 50 mm diameter. Moisture: M-moist, W-wet. Consistency: VS- very soft, S-soft, St-stiff, H-hard.
Figure 3: Borehole BH12, Elevation 1.67 m.
Borehole log legend: Drilling method: W-washbore, T-TC bit. Sample type: U50-undisturbed sample 50 mm diameter. Moisture: M-moist, W-wet. Consistency: VS- very soft, S-soft, St-stiff, H-hard.
Table 1: Particle size distribution and consistency limits test report
1Client:
1Project:
1Location: Home PTY LTD
Riverside Development - Pimpama
BH10, Refer to Map 1Job No.
1Date Checked:
1Checked by: 97638247
19-Jan-2009
Lab Reference No.
B15761 Sample Identification:
Soil origin: Marine BH10: 0.5-1.0 m
Laboratory Specimen Description:
Sandy clay
Particle Size Distribution AS1289 3.6.1 Consistency Limits and Moisture Content
Sieve Size
mm % Passing Specification Test Method Result Spec.
9.5
6.7
4.75
2.36
1.18
0.600
0.425
0.300
0.150
0.075
0.020
0.006
0.002 100
95
92
90
87
77
62
54
49
41 Liquid Limit
Plastic Limit
Linear Shrinkage
Moisture Content
Wet Density
Soil Particle Density %
%
%
%
t/m3t/m3 1AS1289 3.1.2
1AS1289 3.2.1
1AS1289 3.4.1
1AS1289 2.1.1
1AS1289 F4.1
1AS1289 F4.1 39
21
1.4
Table 2
Table 3
2.70 Sample History:
Preparation Method:
Crumbling / Curling of linear shrinkage:
Linear shrinkage mould length: Oven dried (100 deg.)
Dry sieved
Nil
250mm
Table 2: Data from water content tests
Container ID Mass of container, g Mass of wet soil + container, g Mass of dry soil + container, g Water content, %
La1 9.5 28.1 23.9 La2 10.5 26.6 22.8 Average Table 3: Characteristics of soil samples
No Sample mass, g Diameter, mm Height, mm Density, g/cm3 Unit weight, kN/m3
1 308 50.3 100.2 2 313 50.9 100.6 3 303 50.2 100.1 Average
Table 4: Particle size distribution and consistency limits test report
1Client:
1Project:
1Location: Home PTY LTD
Riverside Development - Pimpama
BH10, Refer to Map 1Job No.
1Date Checked:
1Checked by: 97638247
19-Jan-2009
Lab Reference No.
B15761 Sample Identification:
Soil origin: Marine BH10: 2.2-2.7 m
Laboratory Specimen Description:
Silty clay
Particle Size Distribution AS1289 3.6.1 Consistency Limits and Moisture Content
Sieve Size
mm % Passing Specification Test Method Result Spec.
9.5
6.7
4.75
2.36
1.18
0.600
0.425
0.300
0.150
0.075
0.020
0.006
0.002 100
99
99
99
96
95
93
87
81
75 Liquid Limit
Plastic Limit
Linear Shrinkage
Moisture Content
Wet Density
Soil Particle Density %
%
%
%
t/m3t/m3 1AS1289 3.1.2
1AS1289 3.2.1
1AS1289 3.4.1
1AS1289 2.1.1
1AS1289 F4.1
1AS1289 F4.1 67
29
12.8
Table 5
Table 6
2.59 Sample History:
Preparation Method:
Crumbling / Curling of linear shrinkage:
Linear shrinkage mould length: Oven dried (100 deg.)
Dry sieved
Nil
250mm
Table 5: Data from water content tests
Container ID Mass of container, g Mass of wet soil + container, g Mass of dry soil + container, g Water content, %
La3 20.9 41.2 33.1 La4 21.6 33.7 28.9 Average Table 6: Characteristics of soil samples
No Sample mass, g Diameter, mm Height, mm Density, g/cm3 Unit weight, kN/m3
1 291 50.3 100.2 2 300 50.9 100.6 3 295 50.2 100.1 Average
Table 7: Particle size distribution and consistency limits test report
1Client:
1Project:
1Location: Home PTY LTD
Riverside Development - Pimpama
BH10, Refer to Map 1Job No.
1Date Checked:
1Checked by: 97638247
19-Jan-2009
Lab Reference No.
B15761 Sample Identification:
Soil origin: Residual BH10: 2.9-3.4 m
Laboratory Specimen Description:
Sand
Particle Size Distribution AS1289 3.6.1 Consistency Limits and Moisture Content
Sieve Size
mm % Passing Specification Test Method Result Spec.
9.5
6.7
4.75
2.36
1.18
0.600
0.425
0.300
0.150
0.075 100
96
96
95
88
46
2
1 Liquid Limit
Plastic Limit
Linear Shrinkage
Moisture Content
Wet Density
Soil Particle Density
Maximum void ratio
Minimum void ratio %
%
%
%
t/m3t/m3
1AS1289 3.1.2
1AS1289 3.2.1
1AS1289 3.4.1
1AS1289 2.1.1
1AS1289 F4.1
1AS1289 F4.1 Table 8
Table 9
2.56
0.774
0.478 Sample History:
Preparation Method:
Crumbling / Curling of linear shrinkage:
Linear shrinkage mould length: Oven dried (100 deg.)
Dry sieved
Nil
250mm
Table 8: Data from water content tests
Container ID Mass of container, g Mass of wet soil + container, g Mass of dry soil + container, g Water content, %
La5 21.8 35.2 32.9 La6 9.8 28.1 25.0 Average Table 9: Characteristics of soil samples
No Sample mass, g Diameter, mm Height, mm Density, g/cm3 Unit weight, kN/m3
1 374 50.3 100.2 2 383 50.9 100.6 3 372 50.2 100.1 Average
Table 10: Data from a dynamic come penetrometer test. Location: near BH10
Depth, cm Number of blows, Nd Depth, cm Number of blows, Nd
10 6 240 3
20 5 250 4
30 5 260 3
40 5 270 4
50 5 280 4
60 4 290 9
70 5 300 10
80 4 310 11
90 5 320 10
100 5 330 11
110 4 340 12
120 5 350 15
130 4 360 17
140 5 370 19
150 3 380 19
160 4 390 170 4 400 180 5 410 190 6 420 200 4 430 210 5 440 220 5 450 230 3 460 Table 11: Data from standard Proctor compaction tests on borrow sand from Pit 1
Compaction effort: Standard Mould diameter: 103.5 mm
Mould height: 112.9 mm Mass of mould: 4602 g
Test No. 1 2 3 4 5
Mass of compacted soil + mould (g) 6204 6321 6454 6501 6499
Water content (%) 6.7 9.8 13.2 16.8 19.4
Table 12: Compaction control tests
Control test No. Volume of soil, cm3 Mass of wet soil, g Mass of dry soil, g
1 1298 2222 1882
2 1052 1954 1680
Table 13. Results of field tests conducted for BH10
Test type Depth, m Results obtained
Pocket penetrometer (PP) 1.0 0.3 kgf/cm2
Standard Penetration Test (SPT) 2.9 SPT 5,5,6 N=11
Note that SPT was conducted using the following parameters: Free fall of donut-type hammer (Australia), standard sampler, rod length of 4m. The borehole diameter was 100 mm.
Tasks to complete. Total mark = 5.5.
The project includes three major parts which are detailed below.
Part 1. Analysis of subsurface conditions at the proposed site Part 2. Analysis of stress conditions and cyclic stress ratio Part 3. Provide information on embankment construction
1a. Borehole data and cross-section Draw a cross-section along the A-A line; establish the main geological units and groundwater table using the map, borehole logs, and DCP data. Draw the data from the DCP test and provide data analysis of this test.
(1 mark) 2a. Stresses in soil mass. Using the established soil profile and soil properties, calculate the effective vertical and total horizontal stresses at Point A before excavation. Point A is 2.4 m below the ground surface.
(0.6 mark)
Note:
To solve 2a and 2b, assume the following:
- use the soil profile from BH10;- The bulk density of Topsoil (top layer) is 1.80 g/cm3.
- K0 for all soils is 0.9;-The sand layer (depth 2.8-3.5 m) is under artesian pressure with the pressure head measured to be 1 m above the ground water table;3a. Soil compaction. Sand from Pit 1 will be used to build a road embankment. The data from a series of standard Proctor compaction tests on this sand is given in Table 11.
- Determine the maximum dry density and optimum water content for this soil.
- Establish if the results of control tests (Table 12) meet the compaction specification.
(0.6 mark)
Note:
- The compaction specifications require that the dry density of the compacted soil should be greater than or equal to 95% of the maximum dry density while the water content should be within 1.5% of the optimum water content;1b. Geology of the proposed site
- Describe the subsurface conditions (maximum one page) of the studied area with the focus on problematic soil/s and geotechnical issues that may occur during construction. Support your statement using the data from site investigation.
- Discuss the origin of each type of soil and bedrock as well as common geotechnical issues that may occur to each soil type during construction. Use the existing literature to support your statement.
(0.8 mark) 2b. Stresses in soil mass during excavation. Some excavation will be required for embankment construction. Estimate the maximum cut (h) that can be made so that the stability of the soil mass is not lost. Assume that there are no changes in the groundwater conditions during the excavation.
(0.4 mark) 3b. Compaction volume. The natural (in-situ) bulk density of the sand from Pit 1 is 1.55 g/cm3, the natural water content is 7%, and the specific gravity is 2.67.
Estimate the volume of the borrow sand from Pit 1 required for 50000 m3 of embankment.
(0.2 mark)
1c. Soil constituents. Interpret and analyse the laboratory data (Tables 1-9) using the knowledge you have acquired from this course. Determine the soil constituents and basic properties. Complete Table A, which is given in the Report form.
(0.7 mark) 2c. Estimate the cyclic stress ratio of the sand at a depth of 2.9m in BH10 using the SPT data presented in Table 13. Consider an earthquake with a magnitude of 7.0 and the epicentre distance of 15 km from the proposed construction site. Also comment on the liquefaction resistance (will this soil liquefy or not?)
(0.6 mark) 1d. Soil classification. Draw grain-size distribution curves for three soils from Tables 1, 4 and 7, classify each soil type, and complete Table B. Table B is given in the Report form.
(0.6 mark) Report form
Your name Campus (GC or Nathan) Project No.
1-6
1a. Borehole data and cross-section Provide your cross-section (Note that you can draw it by hand or using software. If you scan your drawing, ensure the high quality of the scan). Draw the data from DCP test on a separate page and provide analysis.
1b. Geology of the proposed site
- Describe the subsurface conditions (maximum one page) of the studied area with the focus on problematic soil/s and geotechnical issues that may occur during construction. Support your statement using the data from the borehole logs.
- Discuss the origin of each type of soil and bedrock and common geotechnical issues that may occur to each soil type during excavation/construction. Use the existing literature to support your statement.
1c. Soil constituents. Complete Table A
Table A. Soil constituents and properties.
Summary of soil examination tests Explanation/Notes
Laboratory specimen description Record the name of soil sample (Laboratory specimen description) from Tables 1, 4 and 7
Depth (m) Record the depth at which the soil samples were collected (Tables 1, 4 and 7)
Wet density (g/cm3) Report an average value for each soil type (Tables 3, 6 and 9)
Unit weight (kN/m3) Report an average value for each soil type (Tables 3, 6 and 9)
Moisture content (%) Report an average value for each soil type (Tables 2, 5 and 8)
Dry density (g/cm3) To calculate the soil constituents, use the soil sample size as follows: a diameter of 50 mm, height of 100 mm
Specific gravity Volume of water (m3) Weight of solids (N) Void ratio Degree of saturation (%) Relative density (%) +
Classification based on relative density. Only for coarse-grained soils. Use the data on maximum and minimum void ratio from Table 7
Estimates of soil strength (kPa). When possible, use the pocket penetrometer data to estimate the strength of soil
IMPORTANT: Provide your work-out below for at least one soil to explain how you have obtained your results. Add more pages if necessary.
1d. Soil classification.
- Draw grain-size distribution curves for each soil (three soils, Tables 1, 4 and 7) and attach them to this report.
- Complete Table B.
Table B. Soil classification
Summary of soil classification Explanation/Notes
Laboratory specimen description Record the name of soil sample (Laboratory specimen description) from Tables 1, 4 and 7
Depth (m) Record the depth at which soil samples were collected (Tables 1, 4 and 7)
Gravel, % Determine the amount of each fraction in %
Sand, % Silt, % Clay, % AASHTO Classification:
Use AASHTO symbols
Unified Soil Classification System (USCS): Use USCS symbols
Plasticity index Only for plastic soils
Liquidity index + Classification based on Liquidity index Activity + Classification based on Activity IMPORTANT: Provide your work-out below for at least one soil to explain how you have obtained your results. Add more pages if necessary.
2a. Schematically illustrate the subsurface conditions and calculate the effective vertical and total horizontal stresses at Point A before construction.
Provide your work-out below
2b. Estimate the maximum cut that can be done so that the soil stability is not lost.
Provide your work-out below
2c. Estimate the cyclic stress ratio of the sand
Provide your work-out below
No. Problem Your answer
2a Effective vertical stress at A (kPa) 2a Total horizontal stress at A (kPa) 2b Maximum cut (m) 2c Cyclic stress ratio 2c Will this soil liquefy (answer Yes or No)
3a. Soil compaction. Sand from Pit 1 will be used to build a road embankment.
- Draw a compaction curve for the sand from Pit 1 (Table 11) and attach it to this report.
- Determine the maximum dry density and optimum water content of this sand.
- Establish if the results of control tests (Table 12) meet the compaction specification.
Provide your work-out below.
3b. Compaction volume. Estimate the volume of the borrow sand
Provide your work-out below.
No. Problem Your answer
3a Maximum dry density (kg/cm3) 3a Optimum water content (%) 3a Will the control tests meet the specifications? (Yes or No) 3b Estimated volume of the borrow sand from Pit 1 (m3) Marking criteria. To receive the full mark for this assignment, you are required to correctly perform all tasks. Points will be deducted from the overall mark according to the type of mistake. Students may work on this assignment together; however, each student must produce an individual report (no plagiarism), according to his/her group number.
Task Marking criteria
1a To receive the full mark, you are required to
- Correctly draw a cross-section along the A-A line (note that you can draw it by hand or using software);- Correctly identify the main geological units;- Correctly identify the ground water level (if it exists);- When necessary, spell out all symbols used in the cross-section (use the Legend for this purpose); all lines must be clear and neat; all numbers and text must be proportional to the size of you drawing and easily read; the axis must be labelled and the correct units (when necessary) must be provided
- Correctly plot and interpret data from the DCP test
- No spelling mistakes or typos.
1b To receive the full mark, you are required to discuss subsurface conditions, including:
- Correctly identify and describe all geological units;- Correctly describe the subsurface conditions and properties of soil using the data from the borehole logs. Identify and describe the problematic soil layer/s (if any);- Correctly discuss the origin of each soil type and bedrock. Identify and discuss potential engineering problems that may occur to each geological unit during construction stage. Support your statement with the existing literature;- Maximum one page;- No spelling mistakes and editing errors
1c To receive the full mark, you are required to
- Correctly determine the soil constituents and basic properties and present the obtained results in Table A of the Report form;- Provide detailed step-by-step solutions for at least one soil that clearly indicate how you have arrived at the final answer;- Use correct units;- No spelling mistakes or typos.
1d To receive the full mark, you are required to
- Correctly draw grain-size distribution curves for all three soils (by hand or using software). All lines in your drawings must be clear and neat; all numbers and text must be proportional to the size of you drawing and easily read; the axis must be labelled and the correct units (when necessary) must be provided;
- Correctly identify the amount of each soil fraction. When necessary, identify soil gradation or plasticity;- Correctly classify all three soils using AASHTO and USCS;- Present the obtained results in Table B of the Report form;- No spelling mistakes or typos.
2a To receive the full mark, you are required to
- Correctly calculate the vertical and horizontal stresses at Point A;- Provide detailed solutions which clearly indicate how the final answer was obtained;- Use correct units;- No spelling mistakes or typos.
2b To receive the full mark, you are required to
- Correctly estimate the maximum cut (in m) from the ground surface at which the stability of soil mass is not lost;- Provide detailed solutions which clearly indicate how the answer was obtained;- Use correct units;- No spelling mistakes or typos.
2c To receive the full mark, you are required to
- Correctly estimate the cyclic stress ratio;- Correctly determine of the soil will liquefy during the assumed earthquake;- Use correct units;- No spelling mistakes or typos.
3a To receive the full mark, you are required to
- Correctly interpret the data from standard Proctor compaction tests and draw a standard compaction curve for Sand from Pit 1. All lines in your drawings must be clear and neat; all numbers and text must be proportional to the size of you drawing and easily read; the axis must be labelled and the correct units (when necessary) must be provided.
- Correctly determine the maximum dry density and optimum water content;- Correctly identify if the results of control tests meet the compaction specifications;- Use correct units;- No spelling mistakes or typos.
3b To receive the full mark, you are required to
- Correctly estimate the volume of borrow sand;- Use correct units;- No spelling mistakes or typos.
