**5. Bamboo effects at the slope stability level**

The reinforcement effect ensured by bamboo roots (**Figure 3**) can be expressed in engineering terms as an 'additional cohesion' added to the strength of the non-rooted soil Eq. (1) [27]. Therefore, the total cohesion of a rooted soil will be the sum of the unrooted soil cohesion plus the cohesion increase due to the presence of roots in the soil [27].

The 'additional cohesion' (∆S; Eq. (1)) can be calculated for a known root tensile strength and root area ratio (RAR; the ratio of the surface area of roots crossing the shear plane and shear plane area [28, 27], Eq. (1)) assuming that all the roots cross the shear plane perpendicularly and break during the shearing process. The rooted soil strength value is then used in traditional slope stability analysis methods (e.g. limit equilibrium methods) to determine the overall slope stability:

$$
\Delta S = \text{1.2} \, t\_k \text{ VAR} \tag{1}
$$

where ∆S is added cohesion or increase in shear strength due to the presence of roots in the

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

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

117

The bamboo capacity to improve overall slope stability is limited by its shallow root system. Important effects can be found within the first 0.3–0.5 m depth. Examples of assessment of soil

At the end of the construction stage, when the bamboo culms roots are not yet developed, the slope must be kept stable exclusively by the action of the inert elements and structures used in the bioengineering work. As time progresses, bamboo roots will increase the overall slope stability, and this process can be assessed by using Eq. (1) and traditional slope stability analysis methods.

The current bamboo construction standards published in 2004 by the International Organization for Standardization (ISO) were the first step in the attempt to standardize the use of bamboo in construction [15, 16, 30]. These standards are essentially based on the existing traditional knowledge with an adaptation of the existing ISO timber and timber testing standards for bamboo [31]. These standards cover the basis for design and testing of bamboo and bamboo products and can be used as a basis for further standardization of bamboo as a structural material used in soil bioengineering. ISO 22156: Bamboo, structural design [30], provides basic design guidance for full culm bamboo construction. This standard is supported by ISO 22157-1 Bamboo, determination of physical and mechanical properties, part 1: requirements [15], which specify the test methods necessary for design, and ISO 22157-2 [16], which is essentially a laboratory manual for determining the structural properties of bamboo.

], and RAR is

], tR is average tensile strength of roots per unit area of soil [KN/m2

the ratio of area of roots crossing the shear plane and the shear plane area.

strength increase by bamboo living culms roots can be found in [29].

**Figure 3.** Overall stability check for a bamboo crib wall.

**6. Design standards for bamboo structure calculations**

soil [KN/m2

**Figure 3.** Overall stability check for a bamboo crib wall.

The most popular traditional treatment for enhancing bamboo natural durability is soaking the bamboo in running water for a period of time [19]. This treatment has a significant effect in enhancing durability against decay fungi because it washes off the starch content of the culms [19]. This treatment has little effect on termite attack because these organisms depend merely on cellulose rather than on starch as food source [23]. Traditional techniques for controlling

When bamboo is used as an inert construction material, seasoning (drying) processes are important in order to carefully bring down its moisture content to levels closer to the in service equilibrium moisture content. Seasoning improves bamboo's resistance to biological

The low natural durability of bamboo material can be perfectly accommodated in the bioengineering approach since, in this type of work, just an initial rigidity is pursued and, hence, only temporary structures are usually included in the work design. Once the introduced living plants become established, the vegetation gradually takes over the structural functions of the wooden supports [24, 25]. As time progresses, the inert bamboo culms will deteriorate, and the live bamboo pegs (or poles) will grow and assume the strengthening effect of the initial structure.

In the bioengineering design approach, the load transfer between the initial structural elements and the evolving structural vegetation elements can be calculated using an eco-engineering design scheme for durability [26]. The rapid growth pattern of bamboo species make

The reinforcement effect ensured by bamboo roots (**Figure 3**) can be expressed in engineering terms as an 'additional cohesion' added to the strength of the non-rooted soil Eq. (1) [27]. Therefore, the total cohesion of a rooted soil will be the sum of the unrooted soil cohesion plus

The 'additional cohesion' (∆S; Eq. (1)) can be calculated for a known root tensile strength and root area ratio (RAR; the ratio of the surface area of roots crossing the shear plane and shear plane area [28, 27], Eq. (1)) assuming that all the roots cross the shear plane perpendicularly and break during the shearing process. The rooted soil strength value is then used in traditional slope stability analysis methods (e.g. limit equilibrium methods) to determine the

*<sup>R</sup>* RAR (1)

starch content in felled bamboo include [21]:

• Felling of bamboo during low-sugar content season

• Postharvesting transpiration of bamboo culms

• Water soaking of bamboo

116 Bamboo - Current and Future Prospects

overall slope stability:

• Felling of bamboo at maturity when sugar content is low

attack and limits the amount of drying shrinkage in service [20].

them very suitable for this kind of work approaches and strategies.

the cohesion increase due to the presence of roots in the soil [27].

**5. Bamboo effects at the slope stability level**

Δ*S* = 1.2 *t*

where ∆S is added cohesion or increase in shear strength due to the presence of roots in the soil [KN/m2 ], tR is average tensile strength of roots per unit area of soil [KN/m2 ], and RAR is the ratio of area of roots crossing the shear plane and the shear plane area.

The bamboo capacity to improve overall slope stability is limited by its shallow root system. Important effects can be found within the first 0.3–0.5 m depth. Examples of assessment of soil strength increase by bamboo living culms roots can be found in [29].

At the end of the construction stage, when the bamboo culms roots are not yet developed, the slope must be kept stable exclusively by the action of the inert elements and structures used in the bioengineering work. As time progresses, bamboo roots will increase the overall slope stability, and this process can be assessed by using Eq. (1) and traditional slope stability analysis methods.
