Ground Improvement Techniques

Bujang B.K. Huat, Arun Prasad, Sina Kazemian, Vivi Anggraini

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9780429017964
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This book provides a review of problems during design and construction on problematic soils. Design methods, site investigation, construction and analysis of the various improvement methods available are explained and discussed. Various regions may have different soils with geotechnical problems that differ from those faced in other regions. For example, in Southeast Asia, the common geotechnical problems are those associated with construction on soft clays and organic soils, while in the arid region of the Middle East, problems are generally associated with the desert soils. In the US, the problems are associated with organic soils, expansive and collapsing soils, and shale. Laterite and lateritic soils are especially problematic in Mexico. Similarly, in Europe, for example, the geotechnical problems are associated with loess (France), and organic soil (Germany). A detailed description of various methods of ground improvement has been provided in 11 chapters. Each chapter deals not only with a description of the method but also focuses on region-specific ground problems and suitable ground improvement techniques. Case studies have also been included. One general chapter is dedicated to site investigation, instrumentation, assessment and control. This book will be of value to students and professionals in the fields of civil and geotechnical engineering, as well as to soil scientists and engineering geologists.

Chapter 1
Introduction

An approximate solution to the right problem is more desirable than a precise solution to a wrong problem.

—Anonymous (2001)

1.1 Introduction

Different regions may have different soils with geotechnical problems altogether different from those faced in other regions. For example, in Southeast Asia, the common geotechnical problems are those associated with construction with soft clays, organic soils and peat, while in the arid region of the Middle East, problems are generally associated with the desert (dry) soils. In the United States, there are problems associated with organic soils, expansive and collapsing soils and shale. Laterite and lateritic soils are especially problematic in Mexico. Similarly, in the European Union, geotechnical problems are associated with loess (France) and organic soil (Germany). Figure 1.1 shows a map of the global soil regions.

In Southeast Asia, central Africa, and North and South America, the major soil type is utisols. Utisols, commonly known as “red clay” soils, are soils that have formed in humid areas and are intensely weathered. In India, the major soils types are utisols and vertisols. Vertisols are soils in which there is a high content of expansive clay, known as montmorillonite, which forms deep cracks in drier seasons or years. Vertisols typically form from highly basic rocks, such as basalt. In the case of the Middle East, parts of the United States and eastern Australia, the main soil type is aridisols. Aridisols (or desert soils) are formed in an arid or semi-arid climate. Aridisols dominate the deserts and xeric shrublands which occupy about one-third of the Earth’s land surface. In central Africa and the northern part of South America, oxisols are the common soil type. The main processes of soil formation of oxisols are weathering and humification. Oxisols are always a red or yellowish color due to the high concentration of iron, aluminum oxides and hydroxides. They also contain quartz and kaolin, plus small amounts of other clay minerals and organic matter.

In central Asia, part of the United States, Argentina and Brazil, the common soil type is mollisols. Mollisols form in semi-arid to semi-humid areas, typically under a grassland cover. They are most commonly found in the mid-latitudes: mostly east of the Rocky Mountains in North America; in Argentina (the Pampas) and Brazil in South America; and in Mongolia and the Russian steppes of Asia. Their parent material is typically base-rich and calcareous and includes limestone, loess, or windblown sand. Meanwhile, in the cold north (Alaska and Siberia), gelisols are found. They are soils of very cold climates which are defined as containing permafrost within 2 m of the soil surface.

Figure 1.1 Global soil regions

Source: https://en.m.wikipedia.org/wiki/Soil_science#/media/File%3AGlobal_soil_regions.webp

A brief account of geotechnical problems for some regions is presented next for example. In the case of Southeast Asia, there are two distinctive different geographic regions. The first is mainland Southeast Asia, also known as Indochina, on the Indochinese peninsula; it comprises Cambodia, Laos, Myanmar (Burma), Thailand, Vietnam and West Malaysia (Peninsular Malaysia). The second region is the Malay Archipelago, or Maritime Southeast Asia, which comprises Brunei (on the island of Borneo), East Malaysia (with the Malayan states of Sabah and Sarawak on the northern part of Borneo), all the islands of Indonesia, the Philippines, Singapore and Timor-Leste (East Timor) (www.nationsonline.org). A map of Southeast Asia is shown in Figure 1.2.

The soil engineering problems of Southeast Asia are normally associated with soft ground, namely soft clays (alluvial and marine), silt and shale formation as well as organic soils and peat. Alluvial soils are also found in many coastal regions of the world.

The coastal plain of Peninsular Malaysia, for example, is of very low relief, standing at most a few meters above sea level. The width of the coastal plain varies greatly and can be up to 20 km or more along relatively large stretches of both eastern and western coasts. Large deposits of weak marine clays are encountered throughout Peninsular Malaysia. They are found in Johor, Malacca, Klang, Penang and Alor Star. The properties of Malaysian marine clay soil vary significantly for moist and dry soils.

Figure 1.2 Map showing Southeast Asian countries

Source: https://en.wikipedia.org/wiki/Southeast_Asia#/media/File:Political_Southeast_Asia_Map.webp

Indonesia consists of the main islands of Java, Sumatra, Sulawesi, Irian Jaya and part of Borneo (Kalimantan). Expansive soils are widely distributed in central to west Java, Indonesia. Beside of its swelling potential, expansive soils present in a region of Yogyakarta are highly susceptible to the action of weathering. Under natural conditions, weathering causes soil disintegration and leads to deterioration of its physical and mechanical properties (Muntohar, 2006). Expansive soils may cause heavy distress to engineering constructions. Foundation soils which are expansive will heave and can cause lifting of foundations and other structures during periods of high moisture. Conversely, during periods of falling moisture, expansive soils can collapse, thereby resulting in building settlement. The availability of loose sand deposits along the coastal line of Indonesia is also life-threatening as Indonesia is an earthquake-prone area.

Figure 1.3 Deterioration of clay shale formation

Source: Oktaviani et al. (2018)

Apart from the problematic soft clay and loose sand deposits, Indonesia has also many problematic shale formations. These formations are primarily composed of expandable, smectitic minerals, pyrite and soluble minerals of calcite and siderite (Irsyam, Susila, and Himawan, 2007). During the soil investigation, when unexposed, the shale gives very high standard penetrometer test (SPT) blow counts (normally more than 40–50 blows/ft). However, once excavated, exposed and in contact with water, the strength can easily deteriorate, as shown in Figure 1.3.

Peat is abundantly found along the eastern coast of Sumatra and western coast of Kali-mantan. Peat is estimated to cover 13% of the total land area of Indonesia, one-third of which is found in Kalimantan. The peat of Kalimantan is characterised by a low nutrient status and a low pH. Peat is also found in many countries throughout the world. In the United States, peat is found in 42 states, with a total acreage of 30 million hectares (ha). Canada and Russia are two countries with a large area of peat – 170 and 150 million ha, respectively. In Malaysia, some 3 million ha (about 8%) of the country’s land area is covered with peat. Peat has certain characteristics that sets it apart from most mineral soils and requires special considerations for construction over them. These special characteristics include (Edil, 1994):

1. High natural moisture content (up to 1500%)
2. High compressibility, including significant secondary and tertiary compression
3. Low shear strength (typically S_u = 5–20 kPa)
4. High degree of spatial variability
5. Potential for further decomposition as a result of changing environmental conditions.

Singapore, located in a tropical climate, is dominated by residual soils from two major geological formations: the Bukit Timah granitic formation and the Jurong sedimentary formation. These residual soils constitute two-thirds of Singapore’s land area (Public Works Department, 1976). About 25% of the land area of Singapore is underlain by recent deposits of marine and alluvial origin. The most common of their recent deposits is Singapore marine clay, which is up to 40 m thick. This soft clay is a Quaternary deposit that lies within submarine valleys cut in an old alluvial formation and is locally known as the Kallang formation. Problems often arise in construction in Singapore involving this soft marine clay owing to its low shear strength and high compressibility. The Singapore peaty soils are usually found together with the soft soil deposits of the Kallang formation. The younger peaty soils are usually found at shallow depth of 3–5 m above the upper marine clay, while the older peaty soils are found at a depth of 10 m sandwiched between the upper and lower marine clays (Tan, 1983).

In poor and weak subsoils, the design of a conventional shallow foundation for structures may present problems with respect to both sizing of the foundation as well as control of foundation settlements. Traditionally pile foundations have been employed, but they prove to be too expensive. A more viable alternative to pile foundation in certain situations is to improve the subsoil itself to such an extent that the subsoil would develop an adequate bearing capacity; foundations constructed after subsoil improvement would have resultant settlements within acceptable limits.

Constructions on soft ground, such as building embankments for road, ra...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• 1 Introduction
• 2 Earthworks and field compaction
• 3 Vibro-flotation and dynamic compaction
• 4 Replacement method, stage construction, preloading and drainage
• 5 Fibers and geosynthetics
• 6 Shallow stabilisation
• 7 Deep stabilisation using chemical additives
• 8 Lightweight fills
• 9 Grouting
• 10 Other techniques
• 11 Site investigation, instrumentation, assessment and control
• Index