**2. The São Jose dos Campos RSW**

This section describes and shows monitoring results of an RSW built in the year of 2006, as a part of a road construction in the city of Sao Jose dos Campos, state of Sao Paulo, Brazil [6]. This RSW has 4.2 m height, segmental concrete blocks composing the face, and geogrid as reinforcements and tropical fine-grained lateritic soil as backfill. In the field, the soil compaction was done through a heavy vibratory roller drum Dynapac CA250PD. Other previous studies have also ensured good mechanical behavior of RSWs where fine-grained soil was used as backfill [12–18]. The wall under consideration was extensively instrumented during 2 months (constructive period) to verify its overall performance. The instrumentation consisted of load cells for measurement of the mobilized loads in the reinforcements and blockface, settlement plates, total pressure cells, inclinometers, and topographical marks. The main results obtained are presented and discussed in this chapter. The instrumentation indicates good mechanical performance of the RSW. The wall under analysis has not indicated any structural problems or excessive deformations. In Section 3, some design considerations and comparison of measured load in the reinforcements and predictions are shown.

ku (for unloading), and Rf

**2.2. Instrumentation**

Weight (gf/m2

equals to 0.90 as typical values.

**Table 3.** Physical and mechanical properties of the fabrics (geosynthetic).

Block weight (kgf) 29 Block with\*crushed stone (kgf) 40–50 Compressive strength (MPa) 6–12

**Table 4.** Characteristics of concrete block used as facing.

Dimensions (m) 0.2 height, 0.40 long, 0.40 wide

**Table 2.** Results of plane strain tests performed on the backfill soils.

1.5 k, and Rf

**Soil γ (kN/m<sup>3</sup>**

are hyperbolic parameters obtained from the triaxial tests according

Behavior of Reinforced Soil Wall Built with Fabrics http://dx.doi.org/10.5772/intechopen.79239 97

to the procedure followed in [19]. In the absence of plane strain or triaxial tests, the values of n and k can be selected using the suggestion from [20]. The value of ku can be considered as

**) w (%) ϕ (°) c (kPa) n k k<sup>u</sup> Rf**

A 16.7 20 36 60 0.47 392 588 0.86 B 16.7 20 38 50 0.36 566 849 0.95

Two different PET geogrids were used in this RSW as reinforcements. One was placed in the reinforcement layers 1–3 (bottom to top) and the other in the layers 4–7. In **Table 3**, the characteristics of those fabrics are shown. In **Table 4**, the characteristics of blocks used as facing are also presented. The blocks were filled with crushed stones, in order to increase the pullout

**Figure 4** shows a general view of the wall just after the end of construction. In **Figures 5** and **6**, are shown a cross section and plan view of the wall with the location of the instruments used for monitoring, respectively. The wall has seven layers of reinforcements with 3 m length each. Four of those layers were instrumented, i.e., reinforcement layers 1, 4, 5, and 6 (see **Figure 5**).

) 360 210

Opening size (mm) 20 × 30 20 × 20 Stiffness modulus, J (kN/m) at 5% strain 400 260

resistance of the geogrid-blocks interface and guarantee drainage at the face.

Reinforcement layers 1–3 4–7 Ultimate longitudinal tensile strength (kN/m) 55 35 Ultimate transverse tensile strength (kN/m) 30 20 Elongation at rupture (%) 12.5 12.5

#### **2.1. Overall characteristics of the Sao Jose dos Campos RWS**

In the wall construction, two residual soils were used as backfill, both with high percentage of fines. The yellow sandy clay (soil A) was used from the top of the wall to the 3.2 m depth, and red sandy clay, from 3.2 m depth to the bottom of the wall. In **Table 1**, the grain-size distribution and Atterberg limits (liquid limit, wL, and plasticity index, PI) of those soils are presented. Using the Unified Soil Classification System, both soils were classified as CL (lowplastic clays).

Those backfill soils were tested in laboratory by means of plane strain tests. The plane strain condition is representative of typical wall behavior where the longitudinal length of the wall is much greater than its height. Under these conditions, it is a reasonable assumption the consideration of the absence of longitudinal deformations. The soil specimens used on tests were compacted statically with the same unit weight (γ) and water content (w) verified in the field. In **Table 2**, the results of those tests are shown; where ϕ is the friction angle of the soil (total stress envelope); c is the cohesion of the soil (total stress envelope); n, k (for loading),


**Table 1.** Soil grain size distribution and Atterberg limits.


**Table 2.** Results of plane strain tests performed on the backfill soils.

ku (for unloading), and Rf are hyperbolic parameters obtained from the triaxial tests according to the procedure followed in [19]. In the absence of plane strain or triaxial tests, the values of n and k can be selected using the suggestion from [20]. The value of ku can be considered as 1.5 k, and Rf equals to 0.90 as typical values.

Two different PET geogrids were used in this RSW as reinforcements. One was placed in the reinforcement layers 1–3 (bottom to top) and the other in the layers 4–7. In **Table 3**, the characteristics of those fabrics are shown. In **Table 4**, the characteristics of blocks used as facing are also presented. The blocks were filled with crushed stones, in order to increase the pullout resistance of the geogrid-blocks interface and guarantee drainage at the face.

#### **2.2. Instrumentation**

pore-pressures inside the reinforced soil mass. The drainage system is often composed by a

This section describes and shows monitoring results of an RSW built in the year of 2006, as a part of a road construction in the city of Sao Jose dos Campos, state of Sao Paulo, Brazil [6]. This RSW has 4.2 m height, segmental concrete blocks composing the face, and geogrid as reinforcements and tropical fine-grained lateritic soil as backfill. In the field, the soil compaction was done through a heavy vibratory roller drum Dynapac CA250PD. Other previous studies have also ensured good mechanical behavior of RSWs where fine-grained soil was used as backfill [12–18]. The wall under consideration was extensively instrumented during 2 months (constructive period) to verify its overall performance. The instrumentation consisted of load cells for measurement of the mobilized loads in the reinforcements and blockface, settlement plates, total pressure cells, inclinometers, and topographical marks. The main results obtained are presented and discussed in this chapter. The instrumentation indicates good mechanical performance of the RSW. The wall under analysis has not indicated any structural problems or excessive deformations. In Section 3, some design considerations and

vertical layer of gravel behind the face and a horizontal layer at the RSW bottom.

comparison of measured load in the reinforcements and predictions are shown.

In the wall construction, two residual soils were used as backfill, both with high percentage of fines. The yellow sandy clay (soil A) was used from the top of the wall to the 3.2 m depth, and red sandy clay, from 3.2 m depth to the bottom of the wall. In **Table 1**, the grain-size distribution and Atterberg limits (liquid limit, wL, and plasticity index, PI) of those soils are presented. Using the Unified Soil Classification System, both soils were classified as CL (low-

Those backfill soils were tested in laboratory by means of plane strain tests. The plane strain condition is representative of typical wall behavior where the longitudinal length of the wall is much greater than its height. Under these conditions, it is a reasonable assumption the consideration of the absence of longitudinal deformations. The soil specimens used on tests were compacted statically with the same unit weight (γ) and water content (w) verified in the field. In **Table 2**, the results of those tests are shown; where ϕ is the friction angle of the soil (total stress envelope); c is the cohesion of the soil (total stress envelope); n, k (for loading),

**Soil ≤2 μm (%) ≤20 μm (%) ≤2 mm (%) wL (%) PI (%)** A 42 49 99 38 22 B 42 47 99 49 29

**2.1. Overall characteristics of the Sao Jose dos Campos RWS**

**Table 1.** Soil grain size distribution and Atterberg limits.

plastic clays).

**2. The São Jose dos Campos RSW**

96 Engineered Fabrics

**Figure 4** shows a general view of the wall just after the end of construction. In **Figures 5** and **6**, are shown a cross section and plan view of the wall with the location of the instruments used for monitoring, respectively. The wall has seven layers of reinforcements with 3 m length each. Four of those layers were instrumented, i.e., reinforcement layers 1, 4, 5, and 6 (see **Figure 5**).


**Table 3.** Physical and mechanical properties of the fabrics (geosynthetic).


**Table 4.** Characteristics of concrete block used as facing.

**Figure 4.** General view of the RSW just after construction.

Inclinometers (I1A, I1B, and I2) and magnetic settlement plates (P1–P10) were used to mea-

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Topographical measurements were used for monitoring external horizontal displacements at face (topographic marks were located between the blocks 5 and 6 and between the blocks 13 and 14). **Figure 5** also indicates that the wall foundation is composed by a piled slab (concrete platform), due to the presence of soft soil beneath it. **Figure 6** shows the position of the inclinometers (I1A and I2), the load cells used for monitor the reinforcement load, and the total stress cells (C1–C5), located in the first layer of reinforcement at 3.6 m depth. Four load cells were

sure lateral and vertical movements, respectively.

**Figure 6.** Location of the instruments in the first layer of reinforcement at 3.6 m depth, [6].

positioned along the reinforcement (see **Figure 7**).

**Figure 7.** Load cells positioned along the reinforcement [21].

**Figure 5.** Cross section of instrumented wall: P is settlement plate and I is inclinometer, [6].

**Figure 6.** Location of the instruments in the first layer of reinforcement at 3.6 m depth, [6].

**Figure 4.** General view of the RSW just after construction.

98 Engineered Fabrics

**Figure 5.** Cross section of instrumented wall: P is settlement plate and I is inclinometer, [6].

Inclinometers (I1A, I1B, and I2) and magnetic settlement plates (P1–P10) were used to measure lateral and vertical movements, respectively.

Topographical measurements were used for monitoring external horizontal displacements at face (topographic marks were located between the blocks 5 and 6 and between the blocks 13 and 14).

**Figure 5** also indicates that the wall foundation is composed by a piled slab (concrete platform), due to the presence of soft soil beneath it. **Figure 6** shows the position of the inclinometers (I1A and I2), the load cells used for monitor the reinforcement load, and the total stress cells (C1–C5), located in the first layer of reinforcement at 3.6 m depth. Four load cells were positioned along the reinforcement (see **Figure 7**).

**Figure 7.** Load cells positioned along the reinforcement [21].

A special device was used for monitoring vertical and horizontal forces at the toe of the bockface. A bipartite metallic block replaced one of the concrete-blocks that compose the facing (**Figure 8**). Six load cells were used inside this metallic block, four for vertical and two for horizontal load measurement.

Additional details of the instruments used for monitor load in the reinforcements (geogrid) and at the block-face could be found in [21].

#### **2.3. Monitoring results**

### *2.3.1. Tension on reinforcements*

**Figure 9** shows measured loads in the reinforcement layers at the end of construction (layers 1, 4, 5, and 6, see **Figure 5**). The maximum load recorded was verified in the reinforcement layer 5, and was equal to 7.1 kN/m. Note that the ultimate strength of the geogrid used at the layer 5 was equal to 35 kN/m (**Table 3**). At this layer, the point of maximum tensile load (Tmax) in the reinforcement at this layer was located 1 m far from face. Notice that considering all layers, the position of the Tmax does not exhibit a well-defined pattern with respect to the distance from face. This random behavior may be related to the difference of placement of the geogrid and the backfill compaction layers in the field.

#### *2.3.2. Loads at the toe of the wall facing*

In **Figure 10**, are shown vertical and horizontal loads measured in the instrumented block located at the toe of the block-face during wall construction. The instrumented metallic block is located in the third block-layer and is monitored by six load cells (see **Figures 5** and **8**).

The front (L1 and L2) and rear (L3 and L4) load cells measure the vertical loads acting in the front (V1) and rear (V2) of the block. The load cells (L5 and L6) measured the horizontal load (H) acting in the block. Note that, in **Figure 10**, the front vertical load (V1 = L1 + L2) is often higher that the rear vertical load (V2 = L3 + L4). This behavior is related to the eccentricity of the resultant load due to the self-weight and lateral earth pressure at the interface with the reinforced soil mass that led to an overturn tendency at the block-facing. The dashed line represents the self-weight of the blocks filled with crushed stone, assuming vertical arrangement of the blocks. Notice that the total measured vertical load (V1 + V2) was always higher than

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**Figure 10.** Vertical and horizontal loads measured in the instrumented block during the wall construction [6].

**Figure 9.** Load in reinforcements measured at the end of construction [6].

**Figure 8.** The metallic block used to measure load next to the toe of block-facing: (a) plan view, (b) section view, and (c) block positioned in the field; dimensions in millimeters [6].

**Figure 9.** Load in reinforcements measured at the end of construction [6].

A special device was used for monitoring vertical and horizontal forces at the toe of the bockface. A bipartite metallic block replaced one of the concrete-blocks that compose the facing (**Figure 8**). Six load cells were used inside this metallic block, four for vertical and two for

Additional details of the instruments used for monitor load in the reinforcements (geogrid)

**Figure 9** shows measured loads in the reinforcement layers at the end of construction (layers 1, 4, 5, and 6, see **Figure 5**). The maximum load recorded was verified in the reinforcement layer 5, and was equal to 7.1 kN/m. Note that the ultimate strength of the geogrid used at the layer 5 was equal to 35 kN/m (**Table 3**). At this layer, the point of maximum tensile load (Tmax) in the reinforcement at this layer was located 1 m far from face. Notice that considering all layers, the position of the Tmax does not exhibit a well-defined pattern with respect to the distance from face. This random behavior may be related to the difference of placement of the

In **Figure 10**, are shown vertical and horizontal loads measured in the instrumented block located at the toe of the block-face during wall construction. The instrumented metallic block is located in the third block-layer and is monitored by six load cells (see **Figures 5** and **8**).

**Figure 8.** The metallic block used to measure load next to the toe of block-facing: (a) plan view, (b) section view, and (c)

horizontal load measurement.

*2.3.1. Tension on reinforcements*

*2.3.2. Loads at the toe of the wall facing*

block positioned in the field; dimensions in millimeters [6].

**2.3. Monitoring results**

100 Engineered Fabrics

and at the block-face could be found in [21].

geogrid and the backfill compaction layers in the field.

**Figure 10.** Vertical and horizontal loads measured in the instrumented block during the wall construction [6].

The front (L1 and L2) and rear (L3 and L4) load cells measure the vertical loads acting in the front (V1) and rear (V2) of the block. The load cells (L5 and L6) measured the horizontal load (H) acting in the block. Note that, in **Figure 10**, the front vertical load (V1 = L1 + L2) is often higher that the rear vertical load (V2 = L3 + L4). This behavior is related to the eccentricity of the resultant load due to the self-weight and lateral earth pressure at the interface with the reinforced soil mass that led to an overturn tendency at the block-facing. The dashed line represents the self-weight of the blocks filled with crushed stone, assuming vertical arrangement of the blocks. Notice that the total measured vertical load (V1 + V2) was always higher than the self-weight of the blocks; this increase of vertical load is due to the mobilized friction at the interface of the block-face and backfill. The measured horizontal load at the toe block-face (H) is related to the restrain to the lateral movement at base of the blocks (fix-base condition), as discussed in [22]. Note that in the RSW under analysis, the first block-layer is tied to the concrete slab (see **Figure 2**). At free-base condition, no mobilization of horizontal load at the block-facing would be expected [22–24].

#### *2.3.3. Vertical stresses at the bottom of the wall*

**Figure 11** presents the vertical stress measured by total stress cells (C2–C5, see **Figure 6**) and calculated values using the Meyerhof approach [25] for the first layer of reinforcement (3.6 m depth) at the end of construction. The Meyerhof approach [25] accounts for the eccentricity of the resultant due to the self-weight and the earth pressure exerted by the nonreinforced zone in the wall. The vertical stress provided by Meyerhof [25] is slightly higher than the vertical stress due the self-weight of backfill without any external load. This behavior is due the earth pressure caused by soil behind the reinforced zone. The study carried out by Riccio et al. [6] presents a more deep discussion about this behavior.

*2.3.5. Vertical displacements*

service life [11].

Vertical displacements were measured during and at the end of construction using magnetic settlement plates (P1–P10; see **Figure 5**). Those plates were positioned both in the reinforced zone and the nonreinforced zone. **Figure 13** presents the vertical displacements at the end of construction; the maximum vertical displacement was equal to 18 mm, recorded by the settlement plate P6. Some plates record values equal to zero or less than 2 mm (P4, P7, P8, and P10). Due to the heavy backfill compaction, most of the vertical displacements have occurred during the wall construction. The heavy compaction induces a kind of a preloading of the soil, and it becomes stiffer, preventing additional vertical deformations during the wall

**Figure 13.** Magnetic settlement plates: (a) view in the field; (b) results at the end of construction.

**Figure 12.** Lateral displacements measured by inclinometers and topographic readings at the end of construction.

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#### *2.3.4. Horizontal displacements*

**Figure 12** shows the horizontal displacements measured at the end of wall construction by means of inclinometers (I1A, I1B, and I2; **Figure 5**) and by topographic readings at the end of construction. Significant movements were measured in I1A e I1B near to the face (~60 mm). Topographic readings in the facing at heights of 1.60 and 2.60 m unveil lateral displacements equal to 4 and 22 mm, respectively. The ratio of the lateral displacement in the face and the height of the wall was equal to 1.5%. Moreover, the lateral displacements measured in I2 (nonreinforced zone) were negligible (<2 mm).

**Figure 11.** Measured and calculated vertical stress at the base of the wall at the end of construction (third layer).

**Figure 12.** Lateral displacements measured by inclinometers and topographic readings at the end of construction.

#### *2.3.5. Vertical displacements*

the self-weight of the blocks; this increase of vertical load is due to the mobilized friction at the interface of the block-face and backfill. The measured horizontal load at the toe block-face (H) is related to the restrain to the lateral movement at base of the blocks (fix-base condition), as discussed in [22]. Note that in the RSW under analysis, the first block-layer is tied to the concrete slab (see **Figure 2**). At free-base condition, no mobilization of horizontal load at the

**Figure 11** presents the vertical stress measured by total stress cells (C2–C5, see **Figure 6**) and calculated values using the Meyerhof approach [25] for the first layer of reinforcement (3.6 m depth) at the end of construction. The Meyerhof approach [25] accounts for the eccentricity of the resultant due to the self-weight and the earth pressure exerted by the nonreinforced zone in the wall. The vertical stress provided by Meyerhof [25] is slightly higher than the vertical stress due the self-weight of backfill without any external load. This behavior is due the earth pressure caused by soil behind the reinforced zone. The study carried out by Riccio et al. [6]

**Figure 12** shows the horizontal displacements measured at the end of wall construction by means of inclinometers (I1A, I1B, and I2; **Figure 5**) and by topographic readings at the end of construction. Significant movements were measured in I1A e I1B near to the face (~60 mm). Topographic readings in the facing at heights of 1.60 and 2.60 m unveil lateral displacements equal to 4 and 22 mm, respectively. The ratio of the lateral displacement in the face and the height of the wall was equal to 1.5%. Moreover, the lateral displacements measured in I2

**Figure 11.** Measured and calculated vertical stress at the base of the wall at the end of construction (third layer).

block-facing would be expected [22–24].

102 Engineered Fabrics

*2.3.3. Vertical stresses at the bottom of the wall*

presents a more deep discussion about this behavior.

(nonreinforced zone) were negligible (<2 mm).

*2.3.4. Horizontal displacements*

Vertical displacements were measured during and at the end of construction using magnetic settlement plates (P1–P10; see **Figure 5**). Those plates were positioned both in the reinforced zone and the nonreinforced zone. **Figure 13** presents the vertical displacements at the end of construction; the maximum vertical displacement was equal to 18 mm, recorded by the settlement plate P6. Some plates record values equal to zero or less than 2 mm (P4, P7, P8, and P10). Due to the heavy backfill compaction, most of the vertical displacements have occurred during the wall construction. The heavy compaction induces a kind of a preloading of the soil, and it becomes stiffer, preventing additional vertical deformations during the wall service life [11].

**Figure 13.** Magnetic settlement plates: (a) view in the field; (b) results at the end of construction.
