**2. Principles of soil bioengineering**

Soil bioengineering comprises a diversified group of techniques and land management systems developed by mankind throughout the millennia to use natural systems and elements in order to ensure the safety and functionality of land uses in a context of restricted availability of materials and, particularly, energy.

Soil bioengineering techniques have been used throughout the world with the available plants and construction systems, many times replicated in different continents due to its efficiency and easy construction.

Only in the first decades of the twentieth century, this set of building and land management techniques has been recognized as an integrated engineering approach to many soil stabilization problems, and they started to be systematized, studied and developed.

This situation led to the development of an engineering discipline where 'soil bioengineering has set itself the aim of designing our environment in a "living" way by applying construction methods which are close to nature (…) based on materials which are found in nature and which are combined with technical building materials' [1].

This engineering domain developed from the rediscovery of traditional building and management techniques that use predominantly living plants and vegetation communities as building materials, nowadays, presents a strong evolution with the development of new materials and plant/material combinations, building techniques and innovative domains of application. This domain of engineering combines classical areas of civil engineering (e.g. structures, materials, construction, geological engineering) with biology, integrating a wide diversity of disciplines and specialization domains. The aim is to achieve feasible, efficient durable, self-repairing, resilient, evolving and ecological functional engineering structures that, within strict technical and geotechnical limits, normally fulfil their planed functions with higher efficiency and lower cost [2].

The nature and characteristics of some bamboo communities can present an important ability to soil and slope protection and stabilization, as one can easily confirm by observing devel-

On the other hand, the structural characteristics offered by some woody bamboo species make bamboo a valuable basic construction material in many regions (e.g. India, China and

These characteristics determine that these species and communities can be of high interest for soil and slope protection and reinforcement works, particularly in areas where the bamboo is native. They can be used integrated and fostering natural communities, ensuring efficient soil cover and reinforcement functions through their high, lightly dense culms and their dense

These functions are also of particular interest for soil bioengineering because bamboo has biological characteristics such as a high vegetative propagation ability (making its reproduction very easy) and a rapid growth (allowing for a quick effect on soil cover and root consolidation). Moreover, the structural and physical characteristics of the stems of certain bamboo species turn them into a very effective construction material for complementary soil bioengi-

Therefore, bamboo in its different forms and associated communities, and also in terms of particular species, is of high interest for nature and biodiversity protection (and therefore

Soil bioengineering comprises a diversified group of techniques and land management systems developed by mankind throughout the millennia to use natural systems and elements in order to ensure the safety and functionality of land uses in a context of restricted availability

Soil bioengineering techniques have been used throughout the world with the available plants and construction systems, many times replicated in different continents due to its efficiency

Only in the first decades of the twentieth century, this set of building and land management techniques has been recognized as an integrated engineering approach to many soil stabiliza-

This situation led to the development of an engineering discipline where 'soil bioengineering has set itself the aim of designing our environment in a "living" way by applying construction methods which are close to nature (…) based on materials which are found in nature and

This engineering domain developed from the rediscovery of traditional building and management techniques that use predominantly living plants and vegetation communities as building

tion problems, and they started to be systematized, studied and developed.

which are combined with technical building materials' [1].

ecosystem restoration) as well as for slope protection and stabilization.

oped bamboo forests in mountainous areas with very steep slopes.

Southeast Asia).

and resilient root systems.

106 Bamboo - Current and Future Prospects

neering support structures.

**2. Principles of soil bioengineering**

of materials and, particularly, energy.

and easy construction.

The European Federation for Soil Bioengineering (EFIB) defines soil and water bioengineering as:

*'Typically, plants and parts of plants are used as living building materials, in such a way that, through their development in combination with soil and rock, they ensure a significant contribution to the longterm protection against all forms of erosion. In the initial phase, they often have to be combined with non-living building materials, which may, in some cases, ensure more or less temporarily, most of the supporting functions.*

*The use of organic materials is preferred, because parallel to the development of the vegetation and its increasing stabilization ability, these materials will rot and be reincorporated in the natural biogeochemical cycles. Also preferred are indigenous (autochthonous) and site-specific plants, as they promote a biodiversity suited to the landscape. The planning and construction objectives are the protection and stabilization of land uses and infrastructures as well as the development of landscape elements'* [3].

Soil bioengineering aims, therefore, at ensuring an efficient nature-based solution to the protection of infrastructures. This can be helpful in situations of conflict between opposite needs: the human demand for larger spaces for activities and infrastructures and the natural systems intrinsic need for development space.

Soil bioengineering systems use plants and parts of plants as living building materials as well as introducing and developing functional living communities that are able (*per se* or complemented by a wide variety of materials and structures) to effectively ensure the desired soil and slope protection and consolidation targets. Its goal, as referred therewith, is mainly functional in terms of protecting and integrating within the infrastructure, as well as landscape protection and restoration. Its particular characteristic is the fact that the result of its application is not an inert structure, but a dynamic, resilient living community able to restore itself after disturbances and, if adequately maintained, to ensure a long-term, non-decaying, effective intervention with permanently developing efficiency.

Due to the nature, characteristics and properties of vegetation, it is important to note that bioengineering strategies also have limitations in terms of their effectiveness and application limits. The first one is that only a limited available number of plants from a given habitat have the necessary technical characteristics constraining the potential use of the aimed technical solutions. Secondly, plants, as living organisms, do not behave in a standardized way, limiting the ability to precisely calculate the technical effectiveness of the interventions. Finally, plants have limited ability in terms of root growth, hindering their capacity to stabilize soils to depths larger than 1.5–2 m, depending on the species. It is also important to note that there is a lack of a systematized knowledge on the physical behaviour of plants and particularly of their roots and root systems, when exposed to external forces, despite the promising results of an ever-growing research effort.

These limitations imply the need for the use of complementary structures to help overcome temporarily or permanently—the local adverse conditions. This situation determined the development of a particular segment of the industry related to complementary materials (e.g. organic geotextiles) aimed at reducing the impact of water and soil erosion in the initial development phases of the construction and interventions and to the conception of construction techniques using classical civil engineering approaches and materials in combination with the advantages brought by vegetation.

conditions and the most relevant erosion processes define the set of feasible techniques for a particular site. In a following step, the evaluation of the existing surrounding vegetation is most important for the design, in terms of project limitations, opportunities and potential long-term achievements. Even when bamboo is the main vegetal constructive element, the long-term success of any bioengineering implementation work is based on a wide range of plant species. It is also important to take into account the bioengineering-specific local logistical and economic constraints. Finally, all this gathered and specific site information forms the basis for selection of the appropriate bioengineering technique, plants and materials to use.

The Use of Bamboo for Erosion Control and Slope Stabilization: Soil Bioengineering Works

http://dx.doi.org/10.5772/intechopen.75626

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The use of bamboo to make retaining structures for soil mass or for stream bank erosion control has been practiced in traditional way in various places around the world for long time. Live bamboo stakes, wattle fence, hedge brush layering techniques and bamboo crib walls are most commonly used bioengineering techniques. Several handbooks describe these techniques and can be used as references [4]. However, an engineering design of bamboo retaining structures, such as bamboo crib wall, has not been detailed so far. For this reason,

A live bamboo crib wall is a three-dimensional structure created from untreated bamboos, fill material and live cuttings. Morgan and Rickson [5] described the crib wall as 'a specialized form of gravity-retaining structure using on-site fill material, held within a constructed framework, to provide most of the necessary mass to resist overturning by the weight of both

This crib structure, once filled, acts as a retaining structure and supports the slope. The bamboo and other installed plants provide immediate protection and stability to the structure. However, it has to be taken into account that the structure stability and resistance to failure will be gradually decreasing as its construction materials decompose. As the bamboo elements of a crib wall decompose, the live cuttings of plants or bamboo clumps will grow and proliferate. The resulting root mass will then bind the fill material and the parent soils of the slope into a single continuum, which will have enhanced strength and contribute towards the stability of the slope. **Figure 1** shows the construction steps from a practical application of a

Both freshly cut and seasoned bamboos can be used in the construction of crib walls. Additionally, lime-treated or chemically treated bamboo stems can also be used. However, the bamboo treatments can make the crib wall construction very expensive. Therefore, it is suggested either to use freshly cut green bamboo or air-dried bamboo for crib construction.

The twig and large knots need to be trimmed although it is not necessary to make the stem smooth. Based on the size of the bamboo stems available at the site, it can be used as single stem or a bundle of three bamboos to make the header and stretcher elements in the crib construction. If larger diameters are used, the bamboo crib wall will resemble a wooden log crib wall, and the crib construction procedure will be similar to wooden log crib wall. If single bamboo stem is used for the header and stretcher elements, it is recommended to use uni-

this section is focused on this bamboo bioengineering technique.

**3.1. Live bamboo crib wall materials and construction specification**

form-sized bamboo stems to ensure a uniform thickness of the crib layer.

the slope and the materials'.

bamboo crib wall in Nepal [6, 7].

The main concerns for soil bioengineering are related to soil support, cover, and consolidation, as well as the regulation of the forces and processes (mainly hydrological, hydraulic, and wind-related) that act as disturbance factors.

The main functions fulfilled by the bioengineering approach are the following:


These functions are performed mainly through the action of plant aerial parts and roots as well as the associated soil biota, through their action in soil anchoring, structuring, aggregating, draining, buttressing, and reinforcement. All of these functions, mainly ensured by living autochthonous vegetation, have the complementary advantages of promoting biodiversity and strongly reducing the CO<sup>2</sup> emissions, not only through its capture during construction but also because the techniques and the nature and quantities of the complementary materials used imply a lower production of greenhouse gases and natural resource consumption.
