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

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

header elements in a specified interval as per the design drawings and specifications. After laying the header and stretcher elements, they should be firmly bound together to make a crib frame. The first layer of the crib frame should then be secured by bamboo pegs of appropriate

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After the completion of the first layer of the frame, fill materials should be placed inside the crib frame and compacted by using hand rammer. The fill material should be compacted to about 50–70 mm above the crib elements. After placing the fill, cuttings or seedlings of rooted plants should be placed horizontally on the top of the fill material. The spacing of cuttings should vary between 100 and 300 mm depending upon the size of cuttings and species of the plants used. While placing the second crib layer, the second crib frame should be set inwards to maintain the designed front batter. In this way, a stable vegetative bamboo crib wall can be constructed. After the completion of the topmost layer, an additional layer of soil should be

After the crib wall construction, in dry weather and low soil moisture, it is recommended to irrigate the cuttings and other plants. After the successful establishment of the cuttings, during the initial growing stages, they should be protected from grazing, so that the young plants can grow undisturbed. If some cuttings do not thrive, additional cuttings should be inserted or planted on the wall to ensure green cover of the front face of the wall and stop the washing out of the structure's fill material. If the crib wall settles due to consolidation, an additional fill material should be added on the top of the wall. The vegetated crib wall should be well

In this bioengineering technique, bamboo and plant materials are used as structural elements to take some load and resist earth pressure. This type of crib wall could be used as an alterna-

added to ensure flush finish with the existing slope of the ground.

maintained for at least the first 2 years after construction (**Figure 2**).

**Figure 2.** View of slide at Badikhel/Lalitpur, Nepal, in May 2003 and August 2003 [7].

tive to gabions or masonry retaining walls.

sizes and should be bound with a peg.

*3.1.2. Maintenance*

**Figure 1.** Crib wall construction steps in Thankot (Nepal) 2002 [7].

To secure the bamboo stems together in a bundle or to make the crib form, suitable binding wires, binding materials or nails should be used so that the bamboo stems will not tear apart or break/bend along their length.

In addition to the bamboo and binding wires, the live cuttings or rooted plants (if possible and according to the nature of the plant, longer than the depth of the crib wall to allow penetration into the soil at the back) and suitable fill materials are also required for the construction of crib walls. Generally, locally available slope or cut material is used as fill material for the crib wall construction. However, if the material contains very coarse gravel where roots cannot develop, a layer of fine, organic-rich material or humus material should be placed around the cuttings to promote the root growth. Large stones and boulders are not recommended as fill materials. The fill material should allow some degree of compaction, so that there will be no large voids within the body of the crib structure.

Before starting the crib wall construction, bamboos, binding wires and cuttings should be stockpiled near the construction site. After setting out the layout of the wall, the foundation for the crib wall construction should be prepared according to the requirement of designed dimensions of the crib wall. The depth of foundation trench shall be between 0.3 and 0.5 m, depending upon the height of the bamboo crib wall. The foundation should be inclined at about 10–15° inwards (in-slope) to increase the stability against sliding. It is recommended to have at least one layer of cribs below the existing ground level to prevent the structure from sliding and the foundation from getting undermined by any seepage water.
