**3. Spot improvement using a local resource‐based approach**

### **3.1. Objectives**

If road projects conducted through community initiatives can achieve satisfactory quality, rural roads that government institutes cannot improve because of budget limitations can be improved instead by communities themselves, or by collaboration between the local govern‐ ment and community.

In such road projects, the community itself must manage the selection and procurement of base materials and the compaction of the base and wearing course materials. At this point, geotextile technology can be applied to reinforce the shear strength of the soil material through manual compaction. This method has been applied to rural road infrastructure.

The technology should use local resources and be labour intensive, and simple, enabling community members to perform all aspects of the improvement work. Thus, spot improve‐ ment methods using local resources have been developed to promote community participa‐ tion. Specifically, Do‐nou technology has been applied to rural road infrastructure.

#### **3.2. Methods and implementation**

Matsuoka and Liu [1] found that quality‐controlled soil bags, here called Do‐nou, have high‐ bearing capacities and developed both a theoretical model and a practical formula for calcu‐ lating their capacities. This theory enabled the authors to identify the plastic bags used for crops, fertilizer, sugar, etc. in rural areas of developing countries to be used as Do‐nou bags, thus serving as geotextiles for reinforcing the shear strength of the soil material.

#### *3.2.1. Base course built through manual compaction*

#### *3.2.1.1. Structural design*

The structural design of a base course consisting of Do‐nou is shown in **Figure 5**.

Spot Improvement of Rural Roads Using a Local Resource‐Based Approach: Case Studies from Asia and Africa http://dx.doi.org/10.5772/66109 95

**Figure 6.** Practical manual compaction method for community work.

Layers of Do‐nou filled with locally available gravel form the base, bearing the traffic load and reducing deformation, and thus protecting the subgrade from excessive stresses. The wearing course in turn prevents the Do‐nou from being exposed, whilst providing a smooth and durable road surface. The thickness of the compacted wearing course layer is 50–100 mm, which is appropriate under circumstances in which only manual compaction with hand rammers of small mass is available, and in which the cost of transporting the wearing course material needs to be minimized. This thin wearing course requires frequent but simple maintenance, including filling to restore the gravel lost through erosion due to weather and traffic.

#### *3.2.1.2. Manual compaction*

**3. Spot improvement using a local resource‐based approach**

If road projects conducted through community initiatives can achieve satisfactory quality, rural roads that government institutes cannot improve because of budget limitations can be improved instead by communities themselves, or by collaboration between the local govern‐

In such road projects, the community itself must manage the selection and procurement of base materials and the compaction of the base and wearing course materials. At this point, geotextile technology can be applied to reinforce the shear strength of the soil material through

The technology should use local resources and be labour intensive, and simple, enabling community members to perform all aspects of the improvement work. Thus, spot improve‐ ment methods using local resources have been developed to promote community participa‐

Matsuoka and Liu [1] found that quality‐controlled soil bags, here called Do‐nou, have high‐ bearing capacities and developed both a theoretical model and a practical formula for calcu‐ lating their capacities. This theory enabled the authors to identify the plastic bags used for crops, fertilizer, sugar, etc. in rural areas of developing countries to be used as Do‐nou bags,

manual compaction. This method has been applied to rural road infrastructure.

tion. Specifically, Do‐nou technology has been applied to rural road infrastructure.

thus serving as geotextiles for reinforcing the shear strength of the soil material.

The structural design of a base course consisting of Do‐nou is shown in **Figure 5**.

**3.1. Objectives**

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ment and community.

**3.2. Methods and implementation**

*3.2.1.1. Structural design*

*3.2.1. Base course built through manual compaction*

**Figure 5.** Structural design of road built with Do‐nou.

For civil projects initiated and completed by communities in the poor rural areas of developing countries, the most widely available, efficient, and practical compaction method is the use of a hand rammer with a mass of approximately 10 kg and a base area of approximately 0.04 m2 (for example, a square of 0.2 m per side). Such rammers are dropped from a height of approx‐ imately 0.6 m and accelerated manually (**Figure 6**).

When building a base course using Do‐nou technology, the confinement of the soil material in bags makes this manual compaction method satisfactory for the base course. The manually compacted Do‐nou layer can provide a firm platform for the later compaction of the wearing course.

#### *3.2.1.3. High bearing capacity of Do‐nou*

The tensile strength of the bags enclosing the soil material increases through this compaction process (**Figure 7a**). The soil inside the bag becomes denser, while the bags themselves become taut (**Figure 7b**). When traffic passes across the road surface, the soil material is subjected to passive shear (**Figure 7c**). The stress conditions are shown in **Figure 7d**. According to Matsuoka and Liu [1], the major principal stress 1 at failure can be calculated as follows:

$$
\sigma\_{1f} + \frac{2T}{B} = K\_p \left( \sigma\_{3f} + \frac{2T}{H} \right) \tag{1}
$$

**Figure 7.** Mechanism that generates the bearing capacity of Do‐nou: (a) Do‐nou subject to manual compaction; (b) Do‐ nou after compaction; (c) Do‐nou under traffic load; (d) stress condition of the soil material inside Do‐nou at passive failure.

Therefore,

$$
\sigma\_{1f} = \sigma\_{3f} K\_{\rho} + \frac{2T}{B} \left(\frac{B}{H} K\_{\rho} - 1\right) \tag{2}
$$

where *T* is tensile strength, and *B* and *H* are the width and height, respectively, of the Do‐nou. <sup>=</sup> 1 + sin ∅ / 1 − sin ∅ is the lateral earth pressure ratio in the passive state and ∅ is the internal friction angle of the soil material inside the bag. The bearing capacity of each Do‐nou can be calculated by multiplying σ1*<sup>f</sup>* times the area of the Do‐nou, *B* × *L*, where *L* is the length of the Do‐nou.

As the Do‐nou undergo compaction, the effective vertical and horizontal stresses on the soil material inside the bags increases. Compared to the loose soil incurred in the case of conven‐ tional designs but no compaction with equipment, the shear to which the material inside the Do‐nou is subjected is confined. Moreover, the tensile strength *T* generated in each bag also increases its capacity, as shown by Eq. (2). Thus, by confining the soil in bags, the base course consisting of Do‐nou achieves a higher bearing capacity. The bags act as a geotextile, increasing the shear strength of the soil.

Equation (2) shows that the bearing capacity of each Do‐nou increases as the tensile strength of the textile that makes up the Do‐nou bag increases, and as the ratio of *B/H* and <sup>=</sup> 1 + sin ∅ / 1 − sin ∅ becomes larger, where *Kp* is a positive function of ∅. Thus, bags with higher tensile strengths and granular soil materials with higher internal friction angles are preferred in Do‐nou applications.

#### *3.2.1.4. Do‐nou bags*

*3.2.1.3. High bearing capacity of Do‐nou*

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failure.

Therefore,

of the Do‐nou.

The tensile strength of the bags enclosing the soil material increases through this compaction process (**Figure 7a**). The soil inside the bag becomes denser, while the bags themselves become taut (**Figure 7b**). When traffic passes across the road surface, the soil material is subjected to passive shear (**Figure 7c**). The stress conditions are shown in **Figure 7d**. According to Matsuoka

and Liu [1], the major principal stress 1 at failure can be calculated as follows:

1 3

s

2 2 *f pf*

æ ö += + ç ÷

*T T <sup>K</sup> B H*

 s

**Figure 7.** Mechanism that generates the bearing capacity of Do‐nou: (a) Do‐nou subject to manual compaction; (b) Do‐ nou after compaction; (c) Do‐nou under traffic load; (d) stress condition of the soil material inside Do‐nou at passive

> <sup>2</sup> <sup>1</sup> *f fp <sup>p</sup> T B K K B H*

æ ö =+ - ç ÷

where *T* is tensile strength, and *B* and *H* are the width and height, respectively, of the Do‐nou.

 <sup>=</sup> 1 + sin ∅ / 1 − sin ∅ is the lateral earth pressure ratio in the passive state and ∅ is the internal friction angle of the soil material inside the bag. The bearing capacity of each Do‐nou

1 3

s s

can be calculated by multiplying σ1*<sup>f</sup>*

è ø (1)

è ø (2)

times the area of the Do‐nou, *B* × *L*, where *L* is the length

It was found that bags woven from either polypropylene or polyethylene could be utilized. Such bags are widely used in developing countries for crops, sugar, seeds, and fertilizers. Tensile strength tests confirmed that the fabric used in bags designed to hold 25 kg had sufficient ductility and tensile strength to bear traffic loads [2]. Two widely recognized tensile strength criteria are that a bundle of 1000 bags of width 45 cm and length 60 cm should have a mass of more than 45 kg, and that the fabric should have more than 10 woven threads per inch. Used empty bags represent a geotextile resource that is widely available in the rural communities of developing countries, and these can be employed for road intervention using the Do‐nou technology.

The procedures introduced to fill and compact the Do‐nou mean that each compacted Do‐nou reaches a width and length of 40 cm, a thickness of 10 cm, and a mass of about 20 kg. The Do‐ nou then resembles a boulder in size and weight and is easily to handle. The Do‐nou is laid uniformly on the subgrade to form the base course.

#### *3.2.1.5. Gravel*

Gravel road design manuals usually specify the base and wearing course material in terms of particle size distribution, strength, and plasticity, taking account of climate factors. The thickness of the base course is specified for each type of material based on the strength of the subgrade and the traffic load over the design lifetime, which is generally 5–10 years. Since Do‐ nou technology increases the density and bearing capacity, poorly graded and weaker types of gravel with higher plasticity can be used in base courses at the similar thickness specified in the manuals. Material confined within the Do‐nou bags can be used to fill the spaces between the laid and compacted Do‐nou, as shown in **Figure 5**. The Do‐nou approach therefore widens the range of materials that can be used as the base course.


a Since there is no reinforcement, it would be preferable that the material would comply with the specification as wearing course material in the design manual.

b 'Well‐graded' specified in terms of Gc = (Percent passing 26.5 mm—percent passing 2.0 mm) × percent passing 4.75  mm/100.

c Appropriate plasticity specified in terms of Sp = Linear shrinkage [7] × percent passing 0.425 mm sieve.

dAppropriate coarse particle hardness specified in terms of TIV, TIV <20 means the material is too hard to be broken with a grid roller, while TIV >65 is too soft to resist excessive crushing under traffic.

e Specified in terms of grading curve envelop as shown in **Figure 8**.

**Table 1.** Minor gravel road design for a subgrade where the soaked CBR value is <3 in a wet climate.

For Do‐nou applications, the percentage of angularly shaped particles that can be retained on a 37.5 mm sieve should be minimized, to avoid tearing or puncturing the bags during com‐ paction.

The authors applied the Do‐nou technology to an actual construction project, working with the local community and monitoring the conditions after the work was completed. Minor gravel road design for a subgrade where the soaked CBR value is <3 in a wet climate is shown in **Table 1**. For comparison, the conventional designs based on the design manuals used in Ethiopia [7] and Kenya [8] are also presented. Uniform sand and sandy gravel with the grading curves shown in **Figure 8** were used in the Do‐nou base, even though they fell outside the specified grading curve envelope. Further research is ongoing to extend the method to use of silty clay.

Spot Improvement of Rural Roads Using a Local Resource‐Based Approach: Case Studies from Asia and Africa http://dx.doi.org/10.5772/66109 99

**Figure 8.** Grain size distribution curves of the specified gravel and others.

#### *3.2.1.6. Practical construction procedures for communities*

**Do‐nou technique application**

mass of around 10 kg

sandy material & Do‐

nou bags

Material Available granular and sandy materiala

Traffic range (number of vehicle per day)

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Wearing course

a

b

c

e

mm/100.

paction.

silty clay.

course material in the design manual.

Envisaged compaction means Hand rammer with a

Base Material Available granular and

**Design manual in Ethiopia [7] Design manual in**

<100 <75 50–150

Specified gravel **•** Soaked CBR ≥15 **•** Swelling ≤1.5% **•** Plasticity index <12

Specified gravel

**•** Soaked CBR ≥15

20–65d

Thickness (mm) 200 200 500

Thickness (mm) 50–100 150 150

Since there is no reinforcement, it would be preferable that the material would comply with the specification as wearing

'Well‐graded' specified in terms of Gc = (Percent passing 26.5 mm—percent passing 2.0 mm) × percent passing 4.75 

dAppropriate coarse particle hardness specified in terms of TIV, TIV <20 means the material is too hard to be broken with

For Do‐nou applications, the percentage of angularly shaped particles that can be retained on a 37.5 mm sieve should be minimized, to avoid tearing or puncturing the bags during com‐

The authors applied the Do‐nou technology to an actual construction project, working with the local community and monitoring the conditions after the work was completed. Minor gravel road design for a subgrade where the soaked CBR value is <3 in a wet climate is shown in **Table 1**. For comparison, the conventional designs based on the design manuals used in Ethiopia [7] and Kenya [8] are also presented. Uniform sand and sandy gravel with the grading curves shown in **Figure 8** were used in the Do‐nou base, even though they fell outside the specified grading curve envelope. Further research is ongoing to extend the method to use of

Appropriate plasticity specified in terms of Sp = Linear shrinkage [7] × percent passing 0.425 mm sieve.

**Table 1.** Minor gravel road design for a subgrade where the soaked CBR value is <3 in a wet climate.

a grid roller, while TIV >65 is too soft to resist excessive crushing under traffic.

Specified in terms of grading curve envelop as shown in **Figure 8**.

Roller with a mass of 5 tons

**•** Grading coefficient Gc 16–34b

**•** Maximum grain size 37.5 mm

**•** Grading coefficient Gc 16–34b **•** Shrinkage product Sp 100–365c **•** Treton impact value TIV (%)

**Kenya [8]**

Specified gravel **•** Soaked CBR ≥20 **•** Plasticity index 5–20 **•** Well‐gradede

Same material as base

These procedures were designed to be practical for use in community road initiatives. Efforts are needed to control the moisture content of available granular material and to optimize the wearing course for compaction. Assessment on optimum moisture can be performed visually by observing a sample of the material that is tightly squeezing in the hand. However, access to the water needed to wet the material is sometimes challenging in the field.

The bags are filled with the granular material using a measurement container of 0.016 m3 . The open end of each bag above the fist is then tied with nylon string. These procedures (**Figure 9**) ensure that all of the Do‐nou has the same size and weight, making it easy to lay them uniformly with minimum space between the adjacent Do‐nou.

**Figure 9.** Procedures for filling the Do‐nou bags with granular material: (a) Measurement container; (b) transferring material to bag; (c) open end of the bags above the fist; (d) tying with nylon string; (e) Do‐nou filled with granular material.

Each Do‐nou is then compacted with 15 strokes of a hand rammer. When well compacted, the dimensions of the Do‐nou should be 40 cm × 40 cm × 10 cm. Any remaining space between the compacted Do‐nou is then filled with available gravel material, and the next layer is laid on top.

The wearing course material is spread with a near‐optimum moisture content and is first compacted manually with a hand rammer, then by passing the traffic‐like gravel transportation trucks on the road. Since no specialized compaction equipment is available, the compacted lift thickness cannot be greater than 50 mm.

#### *3.2.2. Retaining wall built with unskilled labour*

Rural road projects often require the constructions of structures such as culverts, bridges and retaining walls [5]. This construction is normally performed using a mix of skilled and unskilled labour and some equipment. When choosing the most appropriate technology for this type of work, it is important to select materials that are locally available and to reduce the amount of materials that need to be transported over long distances.

Retaining walls are normally built using boulders, sand and cement by the worker groups supervised by stonemasons. This process requires the timely delivery of the various materials in appropriate quantities and masonry skills (**Figure 10a**, **b**), putting the construction of retaining walls beyond the resources available to many local communities.

**Figure 10.** Construction of retaining wall: (a) Material for retaining wall with masonry; (b) construction of retaining wall by masonry; (c) construction of retaining wall with Do‐nou; (d) torn bags and cemented material inside bags.

Do‐nou technology, in contrast, increases the range of work that can be undertaken by communities themselves, using only unskilled labour.

When there is no source of stones or boulders within a reasonable distance of the construction site, Do‐nou filled with *in‐situ* soil can be utilized as an alternative.

Unlike boulders, all Do‐nou are rectangular, with uniform dimensions and weights, which make them simple to lie uniformly and to interlock. (**Figure 10c**). Uniform dimensions of Do‐ nou minimize the space between adjacent Do‐nou, which can then be filled with mortar.

To address the vulnerability to ultraviolet light of Do‐nou bags woven from polypropylene or polyethylene, the soil in the bags is mixed with cement. Initially, the soil and cement mix is confined tightly, with tensile strength generated through manual compaction. The mixture solidifies before the Do‐nou bags become prone to tearing (**Figure 10d**).

#### **3.3. Strengths and limitations**

As discussed in Sections 3.1 and 3.2, spot improvement using local resource‐based approach empowers communities living near rural roads to undertake their own improvements. The use of Do‐nou technology in road building and structural work supports this approach. The strengths and limitations are summarized below.

#### *Strengths:*

Each Do‐nou is then compacted with 15 strokes of a hand rammer. When well compacted, the dimensions of the Do‐nou should be 40 cm × 40 cm × 10 cm. Any remaining space between the compacted Do‐nou is then filled with available gravel material, and the next layer is laid

The wearing course material is spread with a near‐optimum moisture content and is first compacted manually with a hand rammer, then by passing the traffic‐like gravel transportation trucks on the road. Since no specialized compaction equipment is available, the compacted lift

Rural road projects often require the constructions of structures such as culverts, bridges and retaining walls [5]. This construction is normally performed using a mix of skilled and unskilled labour and some equipment. When choosing the most appropriate technology for this type of work, it is important to select materials that are locally available and to reduce the

Retaining walls are normally built using boulders, sand and cement by the worker groups supervised by stonemasons. This process requires the timely delivery of the various materials in appropriate quantities and masonry skills (**Figure 10a**, **b**), putting the construction of

**Figure 10.** Construction of retaining wall: (a) Material for retaining wall with masonry; (b) construction of retaining wall by masonry; (c) construction of retaining wall with Do‐nou; (d) torn bags and cemented material inside bags.

amount of materials that need to be transported over long distances.

retaining walls beyond the resources available to many local communities.

on top.

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thickness cannot be greater than 50 mm.

*3.2.2. Retaining wall built with unskilled labour*


#### *Limitations:*

