**8.4 Summary of slope -reinforcement interactions**

Slope - reinforcement interaction analysis is summarized as follows: (i) The critical slip circle for the slope with reinforcement shifts inward and is very different

**35**

embankment.

**Figure 23.**

**Table 5.**

**9. Software for analysis of reinforced slope**

*circle DEF but without considering the effect of reinforcement.*

*Factors of safety and lengths of Geosynthetics.*

*Geoysynthetic Reinforced Embankment Slopes DOI: http://dx.doi.org/10.5772/intechopen.95106*

from that for the unreinforced slope; (ii) The increase in factor of safety is because of the shift of the critical slip circle deep in the slope and involving larger sliding mass. This results from the fact that the slip circle is deeper in to the soil and away from the critical circle corresponding to that for unreinforced embankment soil; As a consequence, the reinforcement force generated becomes much smaller than that estimated based on the length corresponding to that estimated with respect to slip circle for the unreinforced slope; (iii) The effect of providing reinforcement in the slope is two-fold, viz., shifting of critical circle inside of the embankment involving larger slide mass and by increase in stabilizing force/moment due to bond resistance mobilized in the reinforcement; and (iv) It is possible to achieve about 20 to 30% shorter length of the reinforcement without endangering the stability of the embankment slope. The most significant finding of this study is that the reinforcement can be provided from inside and not necessarily from the face of the

3.0 1.22 1.51 1.80 1.41 5.08 4.0 1.22 1.51 1.86 1.48 5.26 5.0 1.22 1.51 1.92 1.46 6.04 **I***: FSmin for unreinforced slope with critical circle ABC;* **II***: FSmin for reinforced slope with critical circle DEF;* **III***: FS for reinforced slope analyzed for circle ABC of unreinforced slope and* **IV***: Reinforced slope analyzed for critical slip* 

**FS Lr, m**

*Slope stability with critical slip circle DEF but without considering the effect of reinforcement.*

**Z0, m I II III IV**

The objective in designing geosynthetic reinforced soil slope is to determine the required long-term strength and layout of the reinforcement apart from finding the critical failure surface. The layout and strength are interrelated rendering many

**Figure 22.** *Critical slip circle for slope with Z0 = 3.0 m, Lr = 5.08 m and FSmin = 1.51.*

*Geoysynthetic Reinforced Embankment Slopes DOI: http://dx.doi.org/10.5772/intechopen.95106*

#### **Figure 23.**

*Slope Engineering*

practically with no shift of the critical circle.

different from that of unreinforced case.

**8.4 Summary of slope -reinforcement interactions**

*Critical slip circle for slope with Z0 = 3.0 m, Lr = 5.08 m and FSmin = 1.51.*

**8.3 Slope-reinforcement interaction**

ment is summarized in **Table 5**.

1.41 (**Figure 23**).

zone is more than that required for generating the required stabilizing force. Hence minimizing Lf = (Lr - Le) by moving point P inside the soil mass and away from the slope face by curtailing length of reinforcement but still maintaining FSmin above 1.50 can lead to economy. Accordingly, for reinforced slope of **Figure 21**. Lr has been curtailed from the face end of the slope. As point P is moved inside gradually by reducing Lr, the critical circle continues to be DEF or close to it (**Figure 22**), i.e.,

The minimum length, Lr which provides FSmin = 1.51 is obtained as 5.08 m (**Figure 22**). Thus about 30% reduction in length of reinforcement is achieved without sacrificing the stability of the embankment slope as FSmin is still the required value of 1.5. Hence length optimization from face end leads to saving of reinforcement length. The circle, ABC, is not the critical for the reinforced slope and thus not acceptable as the critical circle with consideration of reinforcement is

Slope as in **Figure 21** has been analyzed further for the critical slip circle DEF of reinforced slope but without considering the effect of reinforcement to get FS of

The summary of results for various depth of reinforcement from top of embank-

Slope - reinforcement interaction analysis is summarized as follows: (i) The critical slip circle for the slope with reinforcement shifts inward and is very different

The contribution of reinforcement in enhancing the stability of a slope is observed to be twofold: (i) shifting of the critical slip circle deeper in to the slope involving larger slide mass or forward involving smaller slide mass and thus enhancing the factor of safety of the slope and (ii) due to contribution of reinforcement to stabilizing force/moment. FSmin of 1.22 for unreinforced case increases to 1.41 due to shifting of the critical circle to DEF an increase of 15.6%. Secondly the contribution of reinforcement to stabilizing moment/force leads to a further increase in factor of safety from 1.41 to 1.51, a contribution of about 8.2%.

**34**

**Figure 22.**

*Slope stability with critical slip circle DEF but without considering the effect of reinforcement.*


**I***: FSmin for unreinforced slope with critical circle ABC;* **II***: FSmin for reinforced slope with critical circle DEF;* **III***: FS for reinforced slope analyzed for circle ABC of unreinforced slope and* **IV***: Reinforced slope analyzed for critical slip circle DEF but without considering the effect of reinforcement.*

#### **Table 5.**

*Factors of safety and lengths of Geosynthetics.*

from that for the unreinforced slope; (ii) The increase in factor of safety is because of the shift of the critical slip circle deep in the slope and involving larger sliding mass. This results from the fact that the slip circle is deeper in to the soil and away from the critical circle corresponding to that for unreinforced embankment soil; As a consequence, the reinforcement force generated becomes much smaller than that estimated based on the length corresponding to that estimated with respect to slip circle for the unreinforced slope; (iii) The effect of providing reinforcement in the slope is two-fold, viz., shifting of critical circle inside of the embankment involving larger slide mass and by increase in stabilizing force/moment due to bond resistance mobilized in the reinforcement; and (iv) It is possible to achieve about 20 to 30% shorter length of the reinforcement without endangering the stability of the embankment slope. The most significant finding of this study is that the reinforcement can be provided from inside and not necessarily from the face of the embankment.
