**4.3. Mechanical properties of bamboo for soil bioengineering applications**

The strength of bamboo culms, their straightness and their lightness combined with hardness, range and size of hollowness make them potentially suitable for a variety of both structural and nonstructural applications. With good physical and mechanical properties, low shrinkage and good average density, bamboo is well suited to replace wood/timber in soil bioengineering applications.

For example, from more than 100 bamboo species native to India, only around 20 have been systematically tested, and 16 have been found to be adequate for use in construction (**Table 1**, [14]).

The compressive strength of bamboo ranges between 35 and 70 N/mm<sup>2</sup> which is twice to four times the value of most timber species. The range can be explained by the different test methods and used samples. Bamboo with low moisture content has a higher compressive strength than bamboo with high moisture content (https://www.bambooimport.com/en/blog/ what-are-the-mechanical-properties-of-bamboo).

The average tensile strength of bamboo is approximately 160 N/mm<sup>2</sup> which is around three times higher than most conventional construction grade timber materials (https://www.bambooimport.com/en/blog/what-are-the-mechanical-properties-of-bamboo).


**Table 1.** Physical and mechanical properties of Indian bamboos (in round form) [14].

Shear stress parallel to grain is 6–12 N/mm<sup>2</sup> which is approximately 10 times lower than compressive strength and up to 20 times lower than the tensile strength of the same bamboo species. However, the shear strength of bamboo is often twice the value of popular timber species. (https://www.bambooimport.com/en/blog/what-are-the-mechanical-properties-ofbamboo). The bending strength of most bamboo species varies between 50 and 150 N/mm<sup>2</sup> (**Table 2**) and is, on average, twice the magnitude of most conventional structural timber materials. Interspecies variations can be caused by different test methods, sample quality and moisture content of the tested bamboo. (https://www.bambooimport.com/en/blog/ what-are-the-mechanical-properties-of-bamboo).

bamboo was more sensitive to moisture content change for shear strength and less sensitive

**Table 3.** Safe permissible stresses of different categories of green bamboo for structural design (adapted from BIS [14]).

The experimental results show that the tensile strength of bamboo roots decreases with the increase in diameter through a power function. The tensile strength of the tested bamboo

Bamboo, like most lignocellulosic materials, has very low resistance to biological degrading agents. The culms are liable to attack by insects and termites, and above the fibre saturation

Bamboo is more susceptible to decay than timber, due to a lack of natural toxins and its typically thin walls. This means that a small amount of decay can mean a significant percentage

The high sugar and starch content of the bamboo culm explains its low natural durability. There is not much data available on the natural durability of different bamboo species. The natural durability of raw bamboo is low and varies between 1 and 36 months depending on the species, age of culms and climatic conditions [21]. Bamboo is generally destroyed in about 1–2 years when used in the open and in contact with the ground. According to durability classification [22], bamboo falls in class III (non-durable category) with little variation among species. Data about natural durability of some bamboo species obtained from tests of untreated

at ultimate strains of 14–18% [18].

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for compression strength [17].

**4.4. Bamboo natural durability**

change in technical capacity [20].

bamboo poles can be found in [21].

roots ranges between 18 and 30 N/mm<sup>2</sup>

point, they can be deteriorated by strain and rotting fungi [19].

When bamboo is used in green condition, the mechanical values that should be used for design are shown in **Table 3** (adapted from [14]).

Laboratory testing of material properties [15, 16] showed that the compressive and shear strength parallel to the grain were most significantly affected by moisture content, followed by longitudinal tensile modulus and then bending modulus. Age had little effect on the sensitivity of the tensile modulus and bending modulus to moisture content change, while young


**Table 2.** Material properties of different categories of structural bamboo (adapted from BIS [14]).


**Table 3.** Safe permissible stresses of different categories of green bamboo for structural design (adapted from BIS [14]).

bamboo was more sensitive to moisture content change for shear strength and less sensitive for compression strength [17].

The experimental results show that the tensile strength of bamboo roots decreases with the increase in diameter through a power function. The tensile strength of the tested bamboo roots ranges between 18 and 30 N/mm<sup>2</sup> at ultimate strains of 14–18% [18].
