A FI!,A~IHILITY STUDY ON METHObS OF CONSTRUCTION

OVER PEAT SOILS

HABSAH BT. KELI

Thesis Submitted to the Faculty of Engineering,

University Malaysia Sarawak

as a partial fulfillment of the Degree of

Bachelor of Engineering with Honours

(Civil Engineering)

2006

.. t

Special thanks to my parents, brother and sisters and my friends for

The support,

Encouragement,

Competence,

and

Kindness.

Thank you very much.

I

---..,.-_...... --.~.

ACKNOWLEDGEMENTS

First of all, the author would like to thank Allah SWT, The AI-Mighty, with His

companion, guidance and Allah wishes that this final year project can be completed

successfully. The author also like to express her sincere to her supervisor, Mrs.

Norazzlina Bt M. Sa'don for her guidance, suggestion, comment, advises, and ideas from

the beginning of the project until the end. A special thank to Mr. Nelson, JKR's Civil

Engineer for the helpful information and meaningful knowledge that he gave to the

author. Thanks and appreciation to Ms. Niwhora Erica Midai, Planning Engineer at

MUdajaya Corporation Berhad (MCB) for her kindness and valuable information. Advice

and assistant given by Ms. Amiza Buanie is invaluable. Last but not least, my thanks go

to my family and all my friends for the encouragement and help at the time consuming of

the completion of this final year project.

II

ABSTRACT

Peat and organic soil are recognized as an ultimate soft ground and problematic

ground in engineering term. Constructions over peat soil have given a major problem to

engineers in many years as peat are high in compressibility and low shear strength that

may lead to instability characteristic. Research in engineering field have been made to

determine a suitable methods used in construction works over peat soils. The purpose of

this study is to discuss the various methodology of construction used over peat soil. The

methods highlight here includes fill and excavation methods, methods for accelerating

consolidation, ground improvement techniques for reducing deformation, grouting

techniques, application of geosyntetics techniques and soil stabilization. Four case study

of construction over peat and organic soil were summarized and discussed. These include

soil conditions, methods applied, design detailed, settlement monitoring and performance

of methods applied on each location. The selected locations are Mukah at Sarawak,

Dengkil at Putrajaya City, Peninsular Malaysia, Salem, Oregon and Sapporo, Japan.

From the analyses of case study, all the methods applied give an improvement effect on

peat soil and minimize the post construction settlement. The design approach and

recommendation methods for construction over soft soil were presented .

..

111

I

ABSTRAK

Di dalarn bidang kejuruteraan, tanah garnbut dan tanah organik telah dikenalpasti

sebagai tanah lembut dan bermasalah. Kerja-keIja pembinaan di atas tanah gambut telah

memberikan ban yak masalah kepada banyak pihak terutarnanya kepada jurutera-jurutera

awam sejak dahulu lagi disebabkan tanah gambut mempunyai kadar kemampatan yang

tinggi dan kekuatan regangan yang rendah yang mendorong kepada masalah

ketidakstabilan. Kajian di dalam bidang kejuruteraan tentang kaedah yang sesuai

digunakan untuk kerja-keIja pembinaan infrastruktur di atas tanah gambut telah

dijalankan. Matlarnat kajian ini dijalankan adalah untuk mengenalpasti kaedah yang

sesuai untuk kerja-kerja pembinaan di atas tanah garnbut. Di antara kaedah-kaedah yang

akan dibincangkan disini termasuk kaedah menggali dan mengganti tanah lembut dengan

bahan yang lebih sesuai, kaedah mempercepatkan proses pemendapan tanah, kaedah

memperbaiki tanah, kaedah menyuntik permukaan tanah dengan bahan yang sesuai untuk

menarnbahkan kekuatan tanah, pengunaan geosintetik and kaedah menstabilkan tanah.

Empat lokasi telah dipilih untuk kajian kes mengenai pembinaan di atas tanah garnbut

dan tanah organik. Kajian ini termasuk keadaan tanah, kaedah yang digunakan, kajian

mendapan dan perfoman untuk kaedah yang digunakan. Lokasi yang dipilih adalah

Mukah, Sarawak, Putrajaya, Semenanjung Malaysia, Salem, Oregon dan Sapporo, Japan.

Melalui analisis keempat-empat lokasi, kesemua kaedah yang digunakan dapat

mempercepatkan proses pemendapan. Cadangan mengenai kaedah yang sesuai untuk "

pembinaan di atas tanah lembut juga dibentangkan.

IV

I

..

TABLE OF CONTENT

1 INTRODUCTION AND SCOPE OF STUDY

1.1 General 1

1.2 Background 1

1.3 Scope of Present Study 5

FIGURES 7

2 LITERATURE REVIEW

2.1 General 8

2.2 Physical Properties ofPeat Soil 9

2.2.1 Moisture Relationship 9

2.2.2 Bulk Density 9

2.2.3 Porosity 10

2.2.4 Texture and Loss ofIgnition 10

2.2.5 Swelling and Shrinking 11

2.2.6 Irreversible Drying 11

2.2.7 Bearing Capacity and Strength 12

2.2.8 Hydraulic Conductivity 12

2.3 Chemical Properties of Peat Soil 13

2.3.1 Acidity 13

2.3.2 Cation Exchange Capacity and Base Saturation 13

2.3.3 Organic Carbon 14

2.3.4 Nitrogen 14

2.3.5 Sulphur 14

2.3.6 Phosphorus 15

v

Continued

2.3.7 Free Lime 15

2.4 Construction Option on Peat Soil 15

2.4.1 Avoidance 15

2.4.2 Fill and Excavation Techniques 16

2.4.2.1 Excavation and Replacement Method 16

2.4.2.2 Displacement Method 16

2.4.2.3 Surcharge Preloading 16

2.4.2.4 Reduce Driving Force by Light Weight Fill 17

2.4.3 Methods for Accelerating Consolidation 17

2.4.3.1 Vacuum Preloading 17

2.4.3.2 Prefabricated Vertical Drain (PVD) 18

2.4.3.3 Thermal Precompression 19

2.4.4 Ground Improvement Techniques for Reducing Deformation 19

2.4.4.1 Vibro Replacement Stone Column 19

2.4.4.2 Vibrated Concrete Column (VCC) 21

2.4.4.3 Lime Cement Column 21

2.4.4.3 Vibro Pier 22

2.4.4.4 Rammed Aggregate Pier 23

2.4.4.5 Driven Piles 24

2.4.4.6 Continuous Flight Auger 24

2.4.4.7 Micropiles 25

2.4.5 Grouting Techniques 25

2.4.5.1 Jet Grouting 26

2.4.6 Application of Geosyntetics Techniques 27

2.4.6.1 Geotextiles 27

2.4.6.2 Geogrids 29

VI

Continued

2.4.6.3 Geocell 30

2.4.7 Soil Stabilization 30

2.4.7.1 Fly ash 30

2.4.7.2 Portland Cement Concrete 31

2.4.7.3 Lime 31

2.4.7.4 Deep In-Situ Mixing Methods 32

2.5 Conclusions 33

TABLES 34

FIGURES 39

3 METHODOLOGY

3.1 General 50

3.2 Analysis of Case Study 51

3.2.1 Upgrading and Improving of Jalan Oya-Mukah-Balingian, Sarawak 51

3.2.1.1 Project Background 51

3.2.1.2 Ground Profiles 52

3.2.1.3 Excavation and Replacement Method 52

3.2.1.4 Geotextiles 53

3.2.1.5 Surcharge Preloading 54

3.2.1.6 Settlement Markers 54

3.2.1.7 Settlement Records 55

3.2.1.8 Design Details 55

3.2.2 Upgrading The Traffic System at Dengkil, Putrajaya 56

3.2.2.1 Project Background 56

3.2.2.2 Ground Profiles 57

3.2.2.3 Design Details 57

I

Vll

Continued

583.2.3 Warehouse Project in Salem,Oregon.

583.2.3.1 Project Background

583.2.3.2 Ground Profiles

583.2.3.3 Design Details

593.2.4 Highway Project in Suburbs of Sapporo, Japan

3.2.4.1 Project Background 59

3.2.4.2 Ground Profiles 59

3.2.4.3 Design Details 60

TABLES 60

FIGURES 61

4 RESULT AND ANALYSIS

4.1 General 69

4.2 Monitoring Result and Performance of Using Fill and Excavation and 69

Geotextiles Method

4.3 Monitoring Result of Dynamic Replacement and Prefabricated Vertical Drain 70

4.4 Performance of Rammed Aggregate Piers 70

4.5 Performance of Vacuum Consolidation method 71

FIGURES 72

5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 78

5.2 Recommendation 79

TABLES 80

REFERENCES 82

86APPENDIX

Vlll

~_____~I

LIST OF TABLES

Table 2.1 The Comparative Water Absorbing and Water Retaining Capacities of 34

Three Organic Soil Horizons

Table 2.2 Cation exchange capacity values (CEC) at ph 7 of representative peat 34

from temperate and tropical region

Table 2.3 Comparison of CEC values on a weight and per volume basis 34

Table 2.4 Summary of construction methods to modify the embankment loading 35

on the ground

Table 2.5 Summary of construction methods to provide additional structural 35

support to the embankment

Table 2.6 Summary of construction methods to improve the ground condition 36

under the embankment

Table 3.1 Engineering properties of peat in Hokkaido, Japan 60

Table 5.2 Recommendation methods for construction over soft soil 80

IX

I

LIST OF FIGURES

Figure 1.1 Distribution ofPeat in Sarawak 7

Figure 1.2 Profile of Morphology of Drain Organic Soils 7

Figure 2.1 Vacuum Consolidation 39

Figure 2.2 Ground, Water and Air Pressure before and during Vacuum 39

Consolidation

Figure 2.3 Vertical Drain Installations With Horizontal Strip Drain 40

Figure 2.4 Wet Top Feed Construction Method 40

Figure 2.5 Construction of Stone Column 40

Figure 2.6 Vibro Replacement Stone Column 41

Figure 2.7 Construction of Vibrated Concrete Column 41

Figure 2.8 Constructions of Lime Cement Columns 41

Figure 2.9 Construction of Vibro Pier 42

Figure 2.10 Dry Top Feed Method 42

Figure 2.11 Dry Bottom Feed Method 43

Figure 2.12 Subsurface Stress Distribution ofVibro Pier 43

Figure 2.13 Construction Process of Rammed Aggregate Pier 43

Figure 2.14 Driven Pile Installation Method 44

Figure 2.15 Piles to Structure Connection 44

Figure 2.16 Micropiles 44

Figure 2.17 Types ofMicro piles 45

Figure 2.18 Jet Grouting Construction 45

Figure 2.19 Jet Grouting Process 45

Figure 2.20 Geotextiles on Construction 46

Figure 2.21 Woven or Knitted Geotextiles 46

Figure 2.22 Separation Function fo~Geotextiles 46

Figure 2.23 Filtration Function for Geotextiles 47

x

I

LIST OF FIGURES

Continued

Figure 2.24 Drainage Function for Geotextiles 47

Figure 2.25 Reinforcement Function for Geotextiles 47

Figure 2.26 Woven or Welded Geogrids 48

Figure 2.27 Reinforcement using Geogrids 48

Figure 2.28 Geocell Mattress 48

Figure 2.29 Soil Mixing Process 49

Figure 3.1 Location of Project Jalan Oya-Mukah-Balingian, Sarawak 61

Figure 3.2 Peat Soil Profile at Main Road, Section B 62

Figure 3.3 Position of Settlement Markers 63

Figure 3.4 Excavation of Unsuitable Material 64

Figure 3.5 Replacement of Unsuitable Material with Suitable Material 64

Figure 3.6 Laying of Geotextiles at Road A, Section B 65

Figure 3.7 Sandfilling Works at Road A, Section B 65

Figure 3.8 Sandfilling at Section B 66

Figure 3.9 Pre loading of Sand Surcharge at Road A, Section B 66

Figure 3.10 Longitudinal Cross Section Profiles of Putrajaya Project 67

Figure 3.11 Demarcation for Dynamic Replacement Treatment Area 67

Figure 3.12 Demarcation of Zone Treatment Area ofPutrajaya Project 67

Figure 3.13 Soil Profile at Salem Oregon 68

Figure 3.14 Typical Setup of Vacuum Consolidation Method 68

Figure 3.15 Cross Section ofTest Construction Site at Sapporo, Japan 68

Figure 4.1 Summarized ofRoad A profile Vs Chainage 72

Figure 4.2 Summarized of Cumulative Settlement V s Time at Road A (l) 73

Figure 4.3 Summarized of Cumulative Settlement V s Time at Road A (2) 74 ... Figure 4.4 Settlement Vs Log Time ofPutrajaya Project 75

Xl

LIST OF FIGURES

peA

Continued

Figure 4.5 Elapsed Time V s Embankment Construction 75

Figure 4.6 Elapsed Time V s Settlement 75

Figure 4.7 Period of Pump Operation V s Embankment thickness 76

Figure 4.8 Changes of Observed Settlement and Excess Pore Water 76

Figure 4.9 Depth Distribution of Lateral Displacement 76

Figure 4.10 Depth Distribution of Negative Pressure 77

Xll

,.."*

BD

CBR

CEC

CFA

DR

H

N

MARDI

PCC

PVD

SD

TPS

VCC

GLOSSARY

Non Specific Bulk Density

California Bearing Ratio

Cation Exchange Capacity

Continuous Flight Auger

Dynamic Replacement Columns

Organic Content of Soil

Ignition Loss

Malaysian Agriculture Research and Development

Institutes

Portland Cement Concrete

Prefabricated Vertical Drain

Specific Bulk Density

Total Pore Space

Vibrated Concrete Columns

X111

1 INTRODUCTION AND SCOPE OF STUDY

1.1 GENERAL

The main aim of this project is to study on methods .used in construction over

peat soils at the predominant areas. The methods are discussed in order to obtain the

best solutions for constructions that shall be considered economical and availability

during construction time. In this study, four different locations were selected for the

case study analysis based on the construction over peat soil. The selected areas are

Mukah in Sarawak, Dengkil at Putrajaya, 'Peninsular Malaysia and two others

selected areas at overseas are Oregon, United Kingdom and Sapporo, Japan. These

four projects were selected to make a comparison on the settlement behavior

regarding to the different methods applied and discuss the performances of each

methods during construction. The aim is to gives a better understanding on the

behavior of peat soil especially in term of stability and settlement.

It is hope that the objectives of this project is achieved successfully through a

better understanding and appropriate knowledge on the peat characteristic to make

the construction be more manageable.

1.2 BACKGROUND

Peat soils can be divided into two; firstly the material itself, generally

indicated as peat; and secondly its physiographic or geomorphological setting (the

landscape units) which are given a wide variety of names but generally known as

peatswamps (Andriesse, 1988). Chemists and geologists studied peat as a material ~

because of it uses in industrial or energy purposes. Biologist and scientists studied

I

,.." iii 1*

peatswamps as physiographic units and have become a focus of attention for

environmentalists. The study of peat as a soil to be used for agricultural purposes and

managed within a farming system or land utilization type is relatively new.

Agriculturist defined peat as a problem soil with marginal agricultural capability

(Jamaludin, 2002). According to Murtedza et aI., (2002) peat has been alternately

referred to as organic soils and histosols.

Over the years, peat has been alternately referred t6 as organic soils. Peat in

strict definition refer to the accumulation of a purely one hundred percent organic

material and distinction between soil and vegetative accumulation is not clear

(Andriesse, 1988). Andriesse (1988) also indicated that true peat with one hundred

percent organic matter has a low marginal potential for agricultural development. Tie

(1979) refers peat as organic soil that contain at least 65 percent organic matter or

less than 35 percent mineral content. The term organic soils are used which covers a

much wider range of materials than peat or peat soils. In general the terms peat, peat

soils and organic soils are synonyms to avoid conflict in .interpret the meaning of

peat.

The lowland peat occurs in low laying poorly drained depressions or basin in

the coastal areas. Peat soils in Peninsular Malaysia located at coastal areas of the

west and the east coast, especially in West Johore, Kuantan and Pekan districts, the

Rompin-Endau area, northwest Selangor and Trans-Perak areas in the Perak Tengah

and Perak Hilir districts. In Sarawak, peat occurs mainly between the lower stretches

of the main river courses (basin peat) and in poorly drained interior valleys. They are

found in the administrative divisions of Kuching, Samarahan, Sri Aman, Sibu,

Sarikei, Bintulu, Miri and Limbang (Figure l.1). In Sabah, the organic soils are 'i>

2

pi

found on the coastal areas of the Klias peninsular, Krah swamp in Kota Belud, Sugud

and Labuk estuaries and Kinabatangan Floodplain (Jamaludin, 2002).

According to Tai et al (2003), there are two types of peat formed. The

topogeneous (clayey) peat formed under the influenced of floods is distinguished

from the ombrogeneous (fibrous) peat by its clastic sediment contents. The overlying

ombrogeneous peats were formed above tidal flood levels by the accumulation of

plant remains. It consists of a pile up of slightly to moderately decomposed loose

trunks, branches, leaves, roots, fruits and others vegetal remains with little or no

clastic sediments. It is characterized by low bulk density and a low pH. The

topogeneous peat composed of slightly to moderately decomposed leaves, roots,

reeds and wood with no clastic sediments. This type of peat usually more compact

with layered structure (Tai, 2003). According to Mutalib et al (1992) and Soil

Taxonomy, there are three basic kind of organic soil materials with each layer

overlying on the other layer (Figure 1.2). An upper layer of 20-30 cm thick

recognized as sapric are most highly decomposed organic materials consists of 0.2 or

more bulk density and the fiber content averages less than one-third of the volume

before rubbing. Maximum water content when saturated riormally is less than 450

percent on the oven-dry basis. The middle layer, overlain by sapric of 30-40 em

thick consists of semi-decomposed organic materials of the hemic types. Bulk

density is commonly between 0.07 and 0.18 and the fiber content is normally

between one-third and two-thirds of the volume before rubbing. Maximum water

content when saturated ranges from about 450 to 850 percent. A lower layer

recognized as fibric which is mainly large wood fragment decomposed, branches and

tree trunks have a bulk density of less than 0.1, an unrubbed fiber content exceeding "

,."

850 percent to over 3 000 percent of weight of oven-dry material (Mutalib et aI.,

1992).

Technically, peat soil is defined as soft soil because of its instability, high

water content and long time consolidation. Peat soils also posses a variability in

material properties that changes chemically and biologically with time. These

problematic grounds give difficulties in any construction projects as they are highly

compressibility, very low shear strength and ·low heat conductivity (Nathan, 2003).

Other important characteristics are the very high ground water table, low bulk

density and bearing capacity, very acidic, low level of nutrients, shrinkage and

subsidence upon drainage. When lowering of ground water, peat soils shrink and

oxidation process will increase permeability and compressibility in peat soils

(Sunday Tribune, 2003). Research in engineering field have been made to find a

suitable methods used in infrastructural construction over peat soils. These methods

include excavation and replacement method, surface reinforcement and preloading

(geotextiles, geogrids, timber and bamboo mattress), vertical drains (geosyntetic and

sand drain), piled supports, lightweight fill (geocell, vibrated concrete column, stone

and sand column) and stabilization technique by using lime, cement, concrete, fly

ash, shredded waste tyres, geofoams, woodchips and saw dust (Nathan, 2003).

In agricultural sector, peat soils has been widely used for crops with shallow

rooting and fibrous root systems including oil palm, rubber, coconut, paddy,

pineapples, vegetables, cassava, Liberica coffee, mulberry, banana and sago. The

successful cultivation of oils palm has increased the interest in organic soils in Sabah

and Sarawak. Following by the growth of valuable timber called "Ramin"

(contystylus bancanus) in peat swamps area in Sarawak making Malaysia one of the 'i>

world's largest timber exporters since 1980s (Jamaludin, 2002).

4

F

Extraction of peat for industrial purposes and its potential use as a local,

relatively cheap alternative fuel due to its high organic material, are gaining in

importance as other fossil forms of energy are becoming an economic constraint to

development. For this reason attention is given to peat as an energy source and to

aspects of peat extraction, particularly in relation to agricultural usage and the

agricultural potential ofpeatswamps after extraction.

1.3 SCOPE OF PRESENT STUDY

This chapter is mainly about the recent study on varIOUS methods of

construction over peat soils and acquires the information through published works in

order to realistically evaluate the engineering problem in soft ground construction

works. The objective of this project is to determine the suitable methods of

constructions over peat soils that shall be best applied in the real world by

considering time and economic factor. The objectives of this project are stated of

follows:

a) To understand the characteristic and the behavior of peat soil and obtained an

appropriate knowledge through the experimental investigation from published

works or journals.

b) Providing subsurface information of soft ground and subsurface investigation

of soft ground problems. From this information, it will be easier to indicated

and solved the problems regarding the soft ground. .

c) To analyze and differentiate the variability of the method applied over peat

soil through the case study presented. This may lead to proposal and

recommendation for future construction over peat soil and solution that can ~

best applied to solve the problems regarding construction over peat soil.

5

P'

In section 2, consists of literature review, geotechnical properties of peat soils and

construction options used over peat soils. In this section, the construction works are

discussed in detail in order to give full description of method uses and gives better

understanding about method applied over peat soil. In section 3, mainly on the

analysis of case study in four different locations namely; ~ukah, Sarawak, Dengkil

at Putrajaya, Peninsular Malaysia, Oregon, United Kingdom and Sapporo, Japan are

presented. This section discussed about the recent construction applied over peat soil

and the different methods used on each project. In section 4, presents the result and

discussion on the comparison of the settlement behavior between the methods

applied are discussed. Finally, section 5 contains an outline of the conclusions drawn

in these project and the recommendations for the best options for methods of

construction and its application to the real world.

6

FIGURES

DISTRIBUTION OF PEAT SOILS IN SARAWAKt SOUTH CHINA SEA

_ PEATCOILSKA IMANTAN

Figure 1.1 Distribution of peat in Sarawak (Source: Jamaludin, 2002)

sapric

hemic

fibric

I Remnants of decomposing woodl trunks Semi decomposed woodllogltrunk Figure 1.2: Profile of morphology of drain organic soils (Source: Mutalib et al., 1992)

7

2 LITERATURE REVIEW

2.1 GENERAL

This section provides a brief description of construction options used on peat

soil. In recent years, soft ground engineering works have" become more and more

important in many infrastructure projects and housing developments due to

population growth. Constructions in soft ground are invariably carried out with very

low margins of stability as evidenced by large number of earthworks collapses. The

challenges faced by engineering in designing and constructing structure over peat

soils is not an easy task as there are high in compressibility, low shear strength and

high ground water level. This also includes limited accessibility and difficult

trafficiability on road construction. The accessibility to peat areas can be difficult as

the water table can be at, near or above the ground surface (Nathan, 2003). The other

problems are very long time settlements over an extended time period, stability

problems, upthrusting, side flows, vibration damage from construction machinery

and traffic and damage due to earthquakes. These problems require a better

knowledge on planning and management of peatland development.

However, as several studies have" been made by soil scientist and

agriculturalist about peat soils, engineers recognized peat as a problematic ground

that should be avoided. Instead of avoiding the construction over peat soil, it would

be best if the engineers acquire the ground information to evaluate engineering

problems in construction work. This requires a better understanding on peat

characteristic both physical ~nd chemical properties, peat hydrology, and its

potential.

8

I

r

2.2 PHYSICAL PROPERTIES OF PEAT SOILS

2.2.1 Moisture Relationships

Moisture relationships are important for the design of efficient drainage

layouts. In Table 2.1, the maximum moisture or water holding capacity is the amount

of water the soil retains against gravity, based on the oven-dry weight at 105°e. It

can also be defined as the quantity of water held by a soil as a function of the height

of the soil above the surface. The moisture equivalent is determined by placing the

soil in a perforated box and centrifuging it at a force of 1000 times gravity for 40

minutes. The third method measures the amount of water required to saturate a

standard volume of dry peat (100 cm3) and thereafter measure its moisture

equivalent. Table 2.1 shows a comparison between water absorbing and water

retaining capacities of three types of peat where fibric contain higher water contents

than in sapric materials with 1057 percent peat and 289 percent respectively

(Andriesse, 1988).

According to Jamaludin (2002), Malaysian Agriculture Research and

Development Institute (MARDI) concludes that the field moisture content for peat

soils were accounted to range from 100 percent to 1300 percent on a dry weight

basis.

2.2.2 Bulk Density

According to Andriesse (1988), bul~ density depends on the amount of

compaction, the botanical composition of the materials, their degree of

decomposition, and the mineral and moisture contents at the time of sampling. The

bulk density of an organic soil is the weight of a given volume of soil usually ""'

expressed on a dry weight basis in grams per cubic centimeter. Values range from

9

0.05 g/cm3 in very fibric, undecomposed materials to less than 0.5 glcm3 in well

decomposed materials. Andriesse (1964) reported the mean bulk densities for

Sarawak were between 0.09 and 0.12 g/cm3• The higher bulk density value of 7 to 8

percent of a mineral soil implies high pore space in organic material.

2.2.3 Porosity

Total Pore Space (TPS) largely determines the water retention. Fibric

horizons have a high rate of water movement because of the present of large pores.

Large pores collapse on progressive decomposition and total pore space also

decreases (Andriesse, 1988). Total porosity can be expressed as follows:

TPS in 100 cc of soil = [100 (SD - BD)] / SD (Equation 1)

Where,

TPS = Total Pore Space

SD = Specific Bulk Density

BD = Non Specific Bulk Density

Fibric peats in their normal state commonly have a total porosity of 90

percent by volume, whereas sapric materials commonly have less than 85 percent

pores.

2.2.4 Texture and Loss on Ignition

The texture of organic materials is determined on both the organic and the

mineral parts of the soil. The texture of the mineral part is determined by the usual

granulometric method after removal of the organic material. A method to establish

the amount of mineral matter in an organic soil is by loss on ignition (Andriesse, ~

1988). According to Liang (1998), Skempton and Petley (1970), the relationship

10