UNITED STATES OF AMERICA EMBASSY · 3.3 Atterberg Limits ... TP 1 0644846 82922870 1297 TP 2 0644829 82922846 1297 1.2 Tests Conducted The tests conducted included both field and

ASSESSMENT OF GEOTECHNICAL PROPERTIES OF

FOUNDATION SOIL, LUSAKA RESIDENTIAL

PERIMETER WALLS, 32 G WOODLANDS, OFF

MUTENDE ROAD, LUSAKA

for

UNITED STATES OF AMERICA EMBASSY by

MILESTONE ENGINEERING CONSULTANTS

5758 KABOMPO ROAD, KALUNDU

LUSAKA

October 207

ii

Table of Contents Page No.

1 Introduction .................................................................................................................................................. 1

1.1 Background and Reconnaissance survey ............................................................................................ 1

1.2 Tests Conducted ................................................................................................................................... 2

1.3 Location of Trial Pits ........................................................................................................................... 3

2 Trial Pitting, Sampling and Field Testing .................................................................................................. 3

3 Geotechnical Test Results ............................................................................................................................ 3

3.1 Description of Soil Profiles from the excavated trial pits ................................................................... 3

3.2 Grading Analysis .................................................................................................................................. 4

3.3 Atterberg Limits .................................................................................................................................... 5

3.4 Confirmation of the Soil Classification by the Unified Classification System ................................... 5

3.5 Shrinkage Test ...................................................................................................................................... 6

3.6 Penetration Test Results ....................................................................................................................... 6 3.6.1 Standard Penetration Test (SPT) ....................................................................................................... 6 3.6.2 Dynamic Penetration Super Heavy (DPSH) Test ............................................................................. 8 3.6.3 Angle of Internal Friction ............................................................................................................... 10

4 Conclusion and Recommendations on Geotechnical Properties............................................................. 11

BIBLIOGRAPHY ............................................................................................................................................... 12

APPENDICES

Appendix 1 Sieve Analysis

Appendix 2 Atterberg Limits

Appendix 3 Unified Classification Chart

Appendix 4 Charts for estimating Bearing Capacity and Angle of Internal Friction

1

1 Introduction

1.1 Background and Reconnaissance survey

Through a communication of October 2017, the US Embassy requested

Geotechnical Investigations of foundation soils for the proposed Lusaka

Residential Perimeter Walls on property 32 G, off Mutende Road, in Wooodlands,

Lusaka, Zambia.

A reconnaissance survey was conducted on 3rd

October 2017 and the field

investigations were conducted starting the same day. Laboratory testing was

conducted after collection of soil samples.

The land is on the property generally slopes eastwards, and there is one existing

single storey structure on the site. There are both plantation and indigenous trees

on site and there is an existing tennis court on the southern side of the property.

Plates 1 and 4 show the general conditions of the site.

Plate 1 General view towards the East

Plate 2 General vegetation on the eastern side

2

Plate 3 General view from the East

Plate 4 View towards the South

Tables 1 shows coordinates of the penetration (SPT and DPSH) testing points.

Note that Elevation are only indicative; a topographic survey would give accurate

elevations.

Table 1 Coordinates for Penetration Points

Location Eastings Northings Elevation (m)

TP 1 0644846 82922870 1297

TP 2 0644829 82922846 1297

1.2 Tests Conducted

The tests conducted included both field and laboratory tests, as follows:

Field Tests

a) Standard Penetration Test (SPT)

b) Dynamic Penetration Super Heavy (DPSH) Test

Laboratory Tests

a) Particle size distribution

b) Atterberg Limits and Plasticity Index

c) Shrinkage Test

This report covers the findings from both the Field and Laboratory Tests, and

makes recommendations on the bearing capacity and other properties of the

foundation soil.

3

1.3 Location of Trial Pits

Two trial pits were dug on the proposed site, using hand excavation. The trial pits

were sited as per coordinates presented in Table 1, to a maximum depth of 1.5m.

2 Trial Pitting, Sampling and Field Testing

The pits were identified as TP 1 and TP 2. The trial pits were located on the

southern and eastern walls, respectively.

The Standard Penetration Tests (SPTs) were conducted at a depth of 1.5. The

Dynamic Penetration Super Heavy (DPSH) Test was conducted at both locations,

at each trial pit.

The water table was found to be lower than the maximum depth of 1.5m from the

ground surface.

3 Geotechnical Test Results

3.1 Description of Soil Profiles from the excavated trial pits

The descriptions are presented for each of the trial pits, in Tables 2. Plates 5 to 8

show profiles for the two trial pits.

Plate 5 Profile of TP 1

Plate 6 Bottom of TP 1 showing rock

coverage

4

Plate 7 Profile of TP 2

Plate 8 Bottom of TP 2

Table 2.1 Profile of TP 1

Trial Pit No. Level (m) Description

TP 1 0.00-0.20 Overburden layer of light brown silty

sand

0.20-0.80 Slightly moist Yellowish-brown

sandy-clay mixture

0.80-1.50 Compact reddish brown lateritic

gravel weathered schist mixture with

some pebbles

Table 2.2 Profile of TP 2

Trial Pit No. Level (m) Description

TP 2 0.00-0.30 Overburden layer of grayish silty sand

0.30-1.10 Yellowish-brown coarse grained

sandy-clay mixture

1.10-1.50 Reddish brown lateritic gravel with

pebbles

3.2 Grading Analysis

The results for the grading analyses are presented in Figure 1 and Appendix 1, for

the two trial pits. The grading coefficients for the samples could be determined as

D10, the effective size, could not be determined without carrying out the grading

on the finer fraction. Hydrometer analysis is required to determine the grading for

the fine fraction of each sample. From Figure 1, it may be observed from the

grading curves that the percentages passing the No. 200 (0.075 mm) sieve were

more than 50%, indicating fine grained material for the two samples. TP 2

indicated coarser material. Table 3 summarizes the findings on the grading of the

materials.

5

Figure 1 Particle size distribution curves for TP 1 and TP 2

Table 3 Grading Characteristics of Samples from Trial Pits

Trial Pit No. Sample

No.

% passing the No. 200

(0.075 mm) Sieve

Comments

TP 1-1.5m 1 More than 50% Fine Grained

TP 2-1.5m 1 More than 50% Fine Grained

3.3 Atterberg Limits

A summary of the test results for the three trial pits is presented in Table 5 while

details are in Appendix 2. The relevant properties are the Liquid Limits, Plastic

Limits and the Plasticity Indices. It will be noticed that the Liquid Limits were in

the range 29 to 34%, indicating Low Plasticity (Liquid Limit less than 35%). The

Plasticity Index for TP 1 was 12%.

Table 5 Atterberg Limits

Trial Pit No. Liquid

Limit (%)

Plastic

Limit (%)

Plasticity

Index

TP 1-1.5m 29 17 12

TP 2-1.5m 34 - -

3.4 Confirmation of the Soil Classification by the Unified Classification

System

The Unified Classification chart is presented in Appendix 3. The classifications

were determined, based on the Liquid Limits and the Plasticity Indices. Table 6

0 5

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

100

0.0

1

0.1

0

1.0

0

10.0

0

100.0

0

% F

iner

Sieve Size (mm)

PARTICLE SIZE DISTRIBUTION, 32 G OFF MUTENDE RD, WOODLANDS, LUSAKA-TP

1 and TP 2

Pit 1-1.50m

Pit 2-1.50m

6

summarizes the classification for TP 1, based on the Unified Classification system.

TP 2 could not be classified.

Table 6 Unified Classification

Trial Pit

No.

LL

(%)

PI

(%)

Position

relative

to A-line

Unified Classification

TP 1-1.5m 29 12 Above CL

TP 2-1.5m 34 - - -.

The samples indicated Medium Plasticity and based on the Unified Classification

Chart, the samples may be classified as CL Sandy-Clays of Medium plasticity.

3.5 Shrinkage Test

The shrinkage values give an indication of the settlement characteristics of

foundation soils. The higher the plasticity of the soil, the higher the shrinkage

value. Table 7 summarizes the results of the shrinkage test at the indicated depths

for the two trial holes.

Table 7 Shrinkage Values

Sample

No.

Dept

h (m)

Total

mass

dry

sample

(g)

Mass of

material

passing

the 425um

Sieve

% Mass of

material

passing the

425um Sieve

Initial

Length of

specimen

(A), mm

Length of

Oven Dry

Specimen

(B), mm

Linear

Shrinka

ge (%)

100(1-

B/A)

TP 1-1.5m 1.5 150.00 50.00 140 134 4.29

TP 2-1.5m 1.5 150.00 50.00 140 138 1.43

It will be noted that the shrinkage value ranged from 1 to 4 percent, averaging 4%.

This value is acceptable in view of the clayey-sand foundation materials.

3.6 Penetration Test Results

The penetration test was conducted using a tripod, 63.5 kg hammer and

corresponding penetration heads. The Continuous Dynamic Penetration Test

(DPSH) apparatus was used and the number of blows was correlated to the safe

bearing capacity of the soil at various points. The test points were located close to

the trial pits. For these, the tests were conducted from the soil surface to the

required depth, or refusal, at depth increments of 0.3m. For the Standard

Penetration Test (SPT), the depth was conducted at the indicated excavated depth

for each trial pit.

The recorded N values from the SPT were not corrected for effective overburden

pressure to arrive at the bearing capacity.

3.6.1 Standard Penetration Test (SPT)

This test was conducted at the indicated depth for each trial pit. Plates 9 to 12

show the SPT in progress whilst the test results and estimated safe bearing

7

strengths are presented in Table 7. The bearing capacity values are estimated from

the attached charts in Appendix 5, after Terzaghi and Peck.

Plate 9 SPT in progress



Plate 12 SPT in Progress

Table 7 Bearing capacity estimated from Standard Penetration Test

(SPT)

Trial Pit

No.

Depth

(m)

N value Bearing

Capacity (kPa)

TP 1-1.5m 1.50 16 195

TP 2-1.5m 1.50 9 100

8

It will be observed that the bearing capacities at 1.5m ranged from 100 to 245 kPa.

The lowest value of 100 kPa may be due to the relatively moist conditions of the

soil.

3.6.2 Dynamic Penetration Super Heavy (DPSH) Test

The DPSH was conducted next to each trail hole. Plates 13 to 16 show the DPSH

test in progress.

To obtain the equivalent N values in SPT, the test results for DPSH were

correlated to SPT values by a factor, based on Spagnoli (2008). The bearing

capacity values are summarized in Tables 8.

Plate 13 DPSH test in progress at Point 1




9

Table 8.1 Safe Bearing Capacity from DPSH1 Depth (m) DPSH Blows DPSH

mm/Blow

SPT, N

Value

Bearing

Capacity

(kPa)

0.30 21 14 18 215

0.60 22 14 19 225

0.90 19 16 17 210

1.20 10 30 9 100

1.50 14 21 12 130

1.80 11 27 10 110

2.10 17 18 15 180

2.40 13 23 11 120

2.70 14 21 12 130

3.00 18 17 16 195

3.30 20 15 17 210

3.60 23 13 20 230

3.90 16 19 14 165

4.20 20 15 17 210

4.50 22 14 19 225

4.80 23 13 20 230

5.10 31 10 27 350

10

Table 8.2 Safe Bearing Capacity from DPSH2

Depth (m) DPSH Blows DPSH

mm/Blow

SPT, N

Value

Bearing

Capacity

(kPa)

0.30 14 21 12 130

0.60 12 25 10 110

0.90 14 21 12 130

1.20 11 27 10 110

1.50 12 25 10 110

1.80 12 25 10 110

2.10 14 21 12 130

2.40 9 33 8 80

2.70 14 21 12 130

3.00 12 25 10 110

3.30 15 20 13 150

3.60 16 19 14 165

3.90 32 9 28 360

4.20 50 6 43 530

From the test results, it can be observed that the bearing strength obtained from the

DPSH at depths of 1.5m ranged from 110 to 260 kPa and these values are in

agreement with the SPT values. Refusal was at depths of 2.1 to 5.1m from the

ground surface.

3.6.3 Angle of Internal Friction

The angle of internal friction may be approximated from the SPT N values or the

modified ones. Based on the unmodified values, the angles of internal friction

were approximated, as per chart attached from GN Smith in Appendix 5. The

estimated values are presented in Table 9.

Table 9 Estimated Angle of Internal friction from uncorrected SPT N

Values

Trial Pit

Identification No.

Depth

(m)

Number of

Blows, N

Estimated Angle of Internal

Friction, Ø (degrees)

TP 1-1.5m 1.50 16 37

TP 2-1.5m 1.50 9 35

The estimated angles of internal friction based on the unmodified SPT N values

obtained on the site ranged from 35 to 37 degrees at a depth of 1.5m.

11

4 Conclusion and Recommendations on Geotechnical Properties

The trial pits at the proposed site indicated that the water table was lower than the

1.5m depth from the ground surface.

From the grain size distribution characteristics of the samples, the trial pits

exhibited fine grained material, at 1.5m depth.

The samples indicated Low Plasticity and based on the Unified Classification

Chart, one sample may be classified as CL - Inorganic Sandy-clays of Low

plasticity.

The shrinkage values averaged 4%, which appear reasonable for the sandy-clay

soils at a depth of 1.5m.

The SPT indicated bearing capacity values of the range 100 to 195 kPa, at a depth

of 1.5m. The DPSH test indicated bearing values of 110 to 260 kPa at a depth of

1.5m. Thus the SPT and the DPSH tests gave similar results. Refusal was at a

depth of 4.2m from the ground surface. An allowable bearing capacity value of

150 kPa may be assumed for the site.

The estimated angles of internal friction ranged from 35 to 38 Degrees, at a depth

of 1.5m.

12

BIBLIOGRAPHY

Bowles, J E (1982), Foundation Analysis and Design, McGraw Hill Book

Company, USA.

BSI 1377 (1990), Methods of test for soils for Civil Engineering purposes, British

Standards Institution, UK.

BSI 5930 (1981), Code of Practice for Site Investigations, British Standards

Institution, UK

Fleming, WGK et al (1985), Piling Engineering, Surrey University Press, UK.

Gulhati, SK, Engineering Properties of Soils, TATA McGrall-Hill Publishing

Company, 1978.

Smith, GN, Elements of Soil Mechanics for Civil and Mining Engineers, 5th

Edition, Granada publishing Limited, 1982.

Taylor, GD, Construction materials, 1st Edition, Longman Scientific and

Technical, 1991.

Tomlison MJ (1986), Foundation Design and Construction, 5th

Edition, Longman

Group Ltd, UK.

TRRL/ODA (1992), Overseas Road Note 9, A Design Manual for Small Bridges,

TRRL.

13

APPENDIX 1 SIEVE ANALYSES

14


PARTICLE SIZE DISTRIBUTION ANALYSIS

Soil Sample: Pit 1-1.50m

Test No: 1 Mass of Sample (g): 1000.00

Date of Test: 13/10/2017

Location: 32 G Depth: 1.50 m Tested by: Raven

Sieve No

Sieve Opening

(mm)

Mass of Sieve

(g)

Mass of Sieve+Soil

(g)

Mass of soil

Retained (g)

% Retained

Cumulative %

Retained

% Finer

No. 1 37.50 548.00 548.00 0.00 0.00 0.00 100.00

No. 2 26.50 573.80 573.80 0.00 0.00 0.00 100.00

No. 3 19.10 500.80 940.80 440.00 44.00 44.00 56.00

No. 4 12.30 525.80 549.80 24.00 1.20 45.20 54.80

No. 5 9.50 527.50 539.50 12.00 1.60 46.80 53.20

No. 6 4.75 522.80 538.80 16.00 0.60 47.40 52.60

No. 7 2.40 310.10 316.10 6.00 0.30 47.70 52.30

No. 8 1.18 275.70 278.70 3.00 0.20 47.90 52.10

No. 9 0.600 253.80 255.80 2.00 0.10 48.00 52.00

No. 10 0.425 462.30 463.30 1.00 0.20 48.20 51.80

No. 11 0.300 435.60 437.60 2.00 0.80 49.00 51.00

No. 12 0.150 223.90 231.90 8.00 0.50 49.50 50.50

No. 13 0.075 202.10 207.10 5.00 0.00 49.50 50.50

PAN 182.70 182.70 0.00 48.10 97.60

Total

519.00

Washed through sieve 481.00

15


PARTICLE SIZE DISTRIBUTION ANALYSIS

Soil Sample: Pit 2-1.50m

Test No: 1 Mass of Sample (g): 1000.00

Date of Test: 13/10/2017

Location: 32 G Depth: 1.50 m Tested by: Raven

Sieve No

Sieve Opening

(mm)

Mass of Sieve

(g)

Mass of Sieve+Soil

(g)

Mass of soil

Retained (g)

% Retained

Cumulative %

Retained

% Finer

No. 1 37.50 548.00 548.00 0.00 0.00 0.00 100.00

No. 2 26.50 573.80 573.80 0.00 0.00 0.00 100.00

No. 3 19.10 500.80 500.80 0.00 0.00 0.00 100.00

No. 4 12.30 525.80 525.80 0.00 0.00 0.00 100.00

No. 5 9.50 527.50 527.50 0.00 0.20 0.20 99.80

No. 6 4.75 522.80 524.80 2.00 0.50 0.70 99.30

No. 7 2.40 310.10 315.10 5.00 0.60 1.30 98.70

No. 8 1.18 275.70 281.70 6.00 0.50 1.80 98.20

No. 9 0.600 253.80 258.80 5.00 0.20 2.00 98.00

No. 10 0.425 462.30 464.30 2.00 0.30 2.30 97.70

No. 11 0.300 435.60 438.60 3.00 2.00 4.30 95.70

No. 12 0.150 223.90 243.90 20.00 1.80 6.10 93.90

No. 13 0.075 202.10 220.10 18.00 0.00 6.10 93.90

PAN 182.70 182.70 0.00 93.90 100.00

Total

61.00

Washed through sieve 939.00

16

APPENDIX 2 ATTERBERG LIMITS

17

University of Zambia Department of Civil and Environmental Engineering

Project : 32 G

Date: 11/10/2017

BH No.: TP1-1.5m

Depth: 1.50 m

Test No. Initial gauge rdg (mm)

Final gauge rdg (mm)

Penetration (mm)

Mean Penetration

1 4.62 17.66 13.04 13.05 4.56 17.61 13.05 2 4.69 21.75 17.06 17.06 4.73 21.79 17.06 3 4.77 25.80 21.03 21.05 4.84 25.90 21.06 4 4.93 27.98 23.05 23.04 4.89 27.92 23.03

Liquid Limit

Test No. Plate No.

Mass of Plate (g)

mass of plate + wet soil (g)

mass of plate + dry soil (g)

mass of water (g)

mass of solids (g)

moisture Content (%)

Mean Penetration

1 29 2.60 19.10 15.80 3.30 13.20 25 13

2 A10 2.80 19.00 15.60 3.40 12.80 27 17

3 34 2.60 18.90 15.30 3.60 12.70 28 21

4 50 3.00 18.90 15.10 3.80 12.10 31 23

Plastic Limit

Test No. Plate No.

Mass of Plate (g)



mass of water (g)

mass of solids (g)


Mean moisture Content (%)

1 28 2.90 12.60 11.20 1.40 8.30 16.87 17

2 26 2.70 12.80 11.30 1.50 8.60 17.44

Liquid Limit 29

Plastic Limit 17

Plasticity Index 12

0

5

10

15

20

25

30

24 25 26 27 28 29 30 31 32

Me

an

Pe

ne

tra

tio

n (

mm

)

Moisture Content (%)

TP 1-1.5m

18

University of Zambia Department of Civil and Environmental Engineering

Project : 32 G

Date: 11/10/2017

BH No.: TP2-1.5m

Depth: 1.50 m

Test No. Initial gauge rdg (mm)

Final gauge rdg (mm)

Penetration (mm)

Mean Penetration

1 4.91 18.01 13.10 13.10 4.86 17.95 13.09 2 4.97 22.04 17.07 17.06 5.07 22.12 17.05 3 5.18 26.24 21.06 21.06 5.23 26.29 21.06 4 5.31 28.35 23.04 23.04 5.36 28.40 23.04

Liquid Limit

Test No. Plate No.

Mass of Plate (g)



mass of water (g)

mass of solids (g)


Mean Penetration

1 A10 2.80 22.60 17.90 4.70 15.10 31 13

2 28 2.90 22.50 17.70 4.80 14.80 32 17

3 29 2.60 22.50 17.40 5.10 14.80 34 21

4 26 2.70 22.50 17.20 5.30 14.50 37 23

Plastic Limit

Test No. Plate No.

Mass of Plate (g)



mass of water (g)

mass of solids (g)


Mean moisture Content (%)

1 50 2.80

2 34 2.60

Liquid Limit 34

Plastic Limit

Plasticity Index

0

5

10

15

20

25

30

30 31 32 33 34 35 36 37 38

Me

an

Pe

ne

tra

tio

n (

mm

)

Moisture Content (%)

TP 2-1.5m

19

APPENDIX 3 UNIFIED

CLASSIFICATION CHART

1

2

APPENDIX 4 CHARTS FOR ESTIMATING BEARING CAPACITY AND

ANGLE OF INTERNAL FRICTION

3

4

Documents

UNITED STATES OF AMERICA EMBASSY · 3.3 Atterberg Limits ... TP 1 0644846 82922870 1297 TP 2 0644829 82922846 1297 1.2 Tests Conducted The tests conducted included both field and