Soft Soil Improvement using Rigid
Soft Soil Improvement using Rigid Inclusions: Toward an Application forInclusions: Toward an Application for Transport Infrastruc
Transport Infrastructure Construction in ture Construction in VietnamVietnam Van Duy Tran
Van Duy Tran11, Jean-Jacques Richard, Jean-Jacques Richard11, Tung Hoang, Tung Hoang22 1
1
SEFI-INTRAFOR, FAYAT Fondations, Paris, France,
SEFI-INTRAFOR, FAYAT Fondations, Paris, France, [email protected]@sefi-intrafor.fayat.com..
2 2
National University of Civil Engineering, Hanoi, Vietn National University of Civil Engineering, Hanoi, Vietnam.am.
ABSTRACT:
ABSTRACT: Soft soil improvement by vertical rigid inclusions is a widespreadSoft soil improvement by vertical rigid inclusions is a widespread technique in France for reducing and homogenizing surface settlements. This technique in France for reducing and homogenizing surface settlements. This technique consists of a rigid inclusion network associated with a granular earth technique consists of a rigid inclusion network associated with a granular earth platform
platform (so-called (so-called mattress), mattress), intercalated intercalated between between the the reinforced reinforced soil soil and and the the upperupper structure. The overload is transferred partially onto the inclusions through arching structure. The overload is transferred partially onto the inclusions through arching effect occurring in the platform due to shearing mechanisms in the fill. Such a effect occurring in the platform due to shearing mechanisms in the fill. Such a process
process exhibits exhibits an an economic economic and and effective effective solution solution for for large-scale large-scale civil civil worksworks (roadways, railways and industrial building foundations) constructed over soft soils, (roadways, railways and industrial building foundations) constructed over soft soils, especially in cases of requiring rapid construction.
especially in cases of requiring rapid construction.
This paper presents, in the first part, a concise introduction to the soil improvement This paper presents, in the first part, a concise introduction to the soil improvement including general principles, operating mechanisms, calculation rules for the design including general principles, operating mechanisms, calculation rules for the design and execution methods. In the second part, a parametric analysis based on a highway and execution methods. In the second part, a parametric analysis based on a highway construction project in Dong Nai, Vietnam is rigorously performed to show the construction project in Dong Nai, Vietnam is rigorously performed to show the influence of different parameters of the technique such as the thickness of the influence of different parameters of the technique such as the thickness of the granular earth platform and inclusion diameter on the behavior of a rigid granular earth platform and inclusion diameter on the behavior of a rigid inclusion-supported embankment in the aim of highlighting the functioning mode of the new supported embankment in the aim of highlighting the functioning mode of the new improvement solution. This leads to a preliminary design solution of soft soil improvement solution. This leads to a preliminary design solution of soft soil improvement using rigid inclusions for the existing road construction project in improvement using rigid inclusions for the existing road construction project in Vietnam.
Vietnam.
INTRODUCTION INTRODUCTION
The construction of civil works on soft soils necessitates the use of soil improvement The construction of civil works on soft soils necessitates the use of soil improvement techniques aimed at reducing absolute and differential settlements. Rigid inclusions techniques aimed at reducing absolute and differential settlements. Rigid inclusions method has showed its advantages for the construction of transport infrastructures method has showed its advantages for the construction of transport infrastructures and large-scale industrial facilities such as homogenization and reduction of surface and large-scale industrial facilities such as homogenization and reduction of surface settlements, rapid installation and no impact to the environment. Therefore, this settlements, rapid installation and no impact to the environment. Therefore, this technique has strongly grown in France especially after the issue of the design and technique has strongly grown in France especially after the issue of the design and construction guideline
construction guideline – – ASIRI national project [1]. ASIRI national project [1].
In Vietnam, the enormous increase of transport infrastructure construction projects in In Vietnam, the enormous increase of transport infrastructure construction projects in recent times presents a challenge for ground reinforcement techniques in recent times presents a challenge for ground reinforcement techniques in constructing embankments on soft soil areas. Among the ground improvement constructing embankments on soft soil areas. Among the ground improvement methods currently used in Vietnam, Deep Cement Mixing (DCM) method occupies methods currently used in Vietnam, Deep Cement Mixing (DCM) method occupies the majority of market shares due to its relatively good performance and competitive the majority of market shares due to its relatively good performance and competitive cost [2]. However, the quality of DCM columns is difficult to control and dependent cost [2]. However, the quality of DCM columns is difficult to control and dependent significantly of the surrounded soils. In addition, DCM often fails in improving soft significantly of the surrounded soils. In addition, DCM often fails in improving soft
soils rich in organic matters which are widely encountered in the southern Vietnam. soils rich in organic matters which are widely encountered in the southern Vietnam. This problem could be totally remedied by rigid inclusions which differentiate to This problem could be totally remedied by rigid inclusions which differentiate to DCM columns by using grout or concrete inclusions.
DCM columns by using grout or concrete inclusions.
This paper includes a brief description of the principles of the rigid inclusions This paper includes a brief description of the principles of the rigid inclusions technique for soft soil improvement and the specific calculation approach used in technique for soft soil improvement and the specific calculation approach used in practice
practice design in design in France. France. A parametrA parametric ic study of study of the the behavior of behavior of an an embankment onembankment on reinforced foundation based on an existing highway project in the southern Vietnam reinforced foundation based on an existing highway project in the southern Vietnam is then investigated, which allows to propose an application of the rigid inclusions is then investigated, which allows to propose an application of the rigid inclusions technique for this project.
technique for this project.
PRINCIPLE OF THE REINFORCEMENT TECHNIQUE PRINCIPLE OF THE REINFORCEMENT TECHNIQUE Technique description
Technique description
The principle of soft soil improvement by rigid inclusions is shown in Figure 1, The principle of soft soil improvement by rigid inclusions is shown in Figure 1, which is based on the use of a vertical rigid inclusion network inserted into the soft which is based on the use of a vertical rigid inclusion network inserted into the soft soil, a granular earth mattress located between the inclusions and the upper structure. soil, a granular earth mattress located between the inclusions and the upper structure. The structure load is partially transferred onto the rigid inclusions and then down to The structure load is partially transferred onto the rigid inclusions and then down to the bearing layer through arching effects within the mattress and side friction below the bearing layer through arching effects within the mattress and side friction below the top of the inclusions. The load transfer capacity of the mattress depends on its the top of the inclusions. The load transfer capacity of the mattress depends on its thickness and frictional characteristics [3]. The coverage rate that is defined by the thickness and frictional characteristics [3]. The coverage rate that is defined by the proportion of
proportion of the the surface surface covered covered by by the the inclusions inclusions can can be be increased increased by by adding pileadding pile caps. This ratio currently lies
caps. This ratio currently lies in a range of 2% to 10% [1].in a range of 2% to 10% [1].
Geosynthetic reinforcement can be added directly on the heads of inclusions or Geosynthetic reinforcement can be added directly on the heads of inclusions or between
between the the mattress mattress and and the the inclusions. inclusions. The The differential differential settlement settlement between between thethe inclusions and the soft soil induces the tension in the geosynthetic sheet, which is inclusions and the soft soil induces the tension in the geosynthetic sheet, which is involved in the load transfer on the inclusions.
involved in the load transfer on the inclusions.
Skin friction along the rigid inclusions is also implicated in the load transfer Skin friction along the rigid inclusions is also implicated in the load transfer mechanism. Under the structure load, the soft soil settlement is greater than that of mechanism. Under the structure load, the soft soil settlement is greater than that of the inclusions itself; the inclusion tops punch in the mattress. This allows to develop the inclusions itself; the inclusion tops punch in the mattress. This allows to develop a negative friction. In contrast, in the lower part, the inclusions settle more than the a negative friction. In contrast, in the lower part, the inclusions settle more than the surrounding soil and move into the bearing layer, leading to positive friction. A toe surrounding soil and move into the bearing layer, leading to positive friction. A toe resistance is developed in the lower end anchored in the bearing layer.
resistance is developed in the lower end anchored in the bearing layer.
Rigid inclusions are generally made of sand/cement grout or poor concrete, which Rigid inclusions are generally made of sand/cement grout or poor concrete, which can be included eventually steel reinforcement for supporting tension or lateral loads. can be included eventually steel reinforcement for supporting tension or lateral loads. Rigid inclusions are possibly preformed or manufactured in-situ. The design Rigid inclusions are possibly preformed or manufactured in-situ. The design parameters
parameters such such as as inclusion inclusion dimensions, dimensions, spacing, spacing, and and composition composition are are based based uponupon the development of an optimal support distribution between the inclusions and the the development of an optimal support distribution between the inclusions and the surrounding soil to reduce and homogenize surface settlements to within the surrounding soil to reduce and homogenize surface settlements to within the admissible range, and to achieve the desired equivalent deformation modulus of the admissible range, and to achieve the desired equivalent deformation modulus of the soft soil-inclusion composite. In construction reality, the inclusion diameter varies soft soil-inclusion composite. In construction reality, the inclusion diameter varies from 250 to 500 mm and the inclusion depth from 3 up to 30 m.
Installation methods Installation methods
As mentioned below, there are two types of rigid inclusions, preformed or As mentioned below, there are two types of rigid inclusions, preformed or manufactured in-situ by pilling techniques. Preformed inclusions are usually manufactured in-situ by pilling techniques. Preformed inclusions are usually considered in the case of very soft soil to avoid the overconsumption of grout or considered in the case of very soft soil to avoid the overconsumption of grout or concrete and ensure the inclusion integrity. While manufactured in-situ rigid concrete and ensure the inclusion integrity. While manufactured in-situ rigid inclusions are installed into soft
inclusions are installed into soft ground by rigs with specially designed augers, whichground by rigs with specially designed augers, which are displacement and non-displacement rigid inclusions.
are displacement and non-displacement rigid inclusions.
The drilling auger for the construction of displacement rigid inclusions is hollow and The drilling auger for the construction of displacement rigid inclusions is hollow and has a special geometry (Figure 2) allowing to displace soil laterally when screwing has a special geometry (Figure 2) allowing to displace soil laterally when screwing into the soil. On reaching the design depth, the displacement auger is withdrawn and into the soil. On reaching the design depth, the displacement auger is withdrawn and grout/concrete is simultaneously pumped under pressure until the platform level. grout/concrete is simultaneously pumped under pressure until the platform level. Rebar cage can be eventually installed into the fresh grout/concrete. During Rebar cage can be eventually installed into the fresh grout/concrete. During construction, displacement inclusion strength is greatly enhanced by the construction, displacement inclusion strength is greatly enhanced by the displacement of soil laterally and the pressure grout/concrete effect [4].
displacement of soil laterally and the pressure grout/concrete effect [4].
The non-displacement rigid inclusion is usually constructed by continuous flight The non-displacement rigid inclusion is usually constructed by continuous flight auger (CFA) method whose drilling tool is composed of a hollow central shaft and a auger (CFA) method whose drilling tool is composed of a hollow central shaft and a surrounding helical flight system. The constructive sequence of non-displacement surrounding helical flight system. The constructive sequence of non-displacement inclusions is similar to that of displacement inclusions except that the soil spoil is not inclusions is similar to that of displacement inclusions except that the soil spoil is not displaced laterally but is loaded onto the flights to the surface level. The displaced laterally but is loaded onto the flights to the surface level. The grout/concrete pump is also carried out simultaneously with the auger extraction grout/concrete pump is also carried out simultaneously with the auger extraction (Figure 3).
(Figure 3).
In case of enlarged head inclusions, squared concrete slabs are usually added on the In case of enlarged head inclusions, squared concrete slabs are usually added on the heads of the inclusions, which necessitates two separate interventions (completion of heads of the inclusions, which necessitates two separate interventions (completion of the inclusion and installing the precast slab) and is difficult to set up. In order to the inclusion and installing the precast slab) and is difficult to set up. In order to reduce the construction time, a particular
reduce the construction time, a particular construction method for producing enlargedconstruction method for producing enlarged head inclusions in a single operation has been developed to achieve the rigid circular head inclusions in a single operation has been developed to achieve the rigid circular inclusions associated with a cone shaped head (Rigid Inclusion with Variable Inertia inclusions associated with a cone shaped head (Rigid Inclusion with Variable Inertia - INIV inclusion). Such a method has been successfully applied in a pile-supported - INIV inclusion). Such a method has been successfully applied in a pile-supported road project near Bourgoin-Jallieu in France [5].
road project near Bourgoin-Jallieu in France [5].
During rigid inclusion construction, real-time monitoring and recording of drilling During rigid inclusion construction, real-time monitoring and recording of drilling and extraction parameters such as drilling depth, pressure, grout/concrete volumes, and extraction parameters such as drilling depth, pressure, grout/concrete volumes, advancement speed, auger rotation and downward force of the rotor torque of the advancement speed, auger rotation and downward force of the rotor torque of the auger are also performed, which ensures a hi
auger are also performed, which ensures a high quality control of the construction.gh quality control of the construction. CALCULATION METHODS
CALCULATION METHODS
The rigid inclusion reinforcement behavior is commonly studied in a complete The rigid inclusion reinforcement behavior is commonly studied in a complete manner by numerical models in continuous medium such as finite element and manner by numerical models in continuous medium such as finite element and different element methods which allow to account for the entire configuration of the different element methods which allow to account for the entire configuration of the reinforced soil, rigid inclusions and the interfaces between the different components reinforced soil, rigid inclusions and the interfaces between the different components
as well as the structure construction history. However, numerical methods require a as well as the structure construction history. However, numerical methods require a dedicated implementation of soil-structure simulation including the relevance of the dedicated implementation of soil-structure simulation including the relevance of the adopted soil constitutive models and the quality of soil parameter input data. This adopted soil constitutive models and the quality of soil parameter input data. This causes many difficulties in practice design for geotechnical engineers. Therefore, the causes many difficulties in practice design for geotechnical engineers. Therefore, the French guideline ARISI proposes an analytical approach to model the load
French guideline ARISI proposes an analytical approach to model the load transfer intransfer in soil reinforced by rigid inclusions which is in good agreement with the numerical soil reinforced by rigid inclusions which is in good agreement with the numerical results.
results.
The principle is to consider an elementary reinforced cell centered by an inclusion, The principle is to consider an elementary reinforced cell centered by an inclusion, which is subjected to a vertical uniform load. This cell is decomposed in two which is subjected to a vertical uniform load. This cell is decomposed in two sub-domains: the inclusion and the soil parts extended up to the top or bottom domains: the inclusion and the soil parts extended up to the top or bottom boundaries, and the all remaining soil volume (Figure 4). The interaction between the boundaries, and the all remaining soil volume (Figure 4). The interaction between the
two sub-domains is assumed to be fully described by the shear stress
two sub-domains is assumed to be fully described by the shear stress τ τ which is which is
developed on their interface. The elementary cell is assimilated to an equivalent developed on their interface. The elementary cell is assimilated to an equivalent cylinder. The model is assumed to be periodic which implies that both lateral cylinder. The model is assumed to be periodic which implies that both lateral deformations and shear stresses are vanished at the exterior boundaries.
deformations and shear stresses are vanished at the exterior boundaries.
The equilibrium state is described by the variation of forces within the inclusion The equilibrium state is described by the variation of forces within the inclusion (Equation 1) and the soil (Equation 2)
(Equation 1) and the soil (Equation 2)
where
where τ τ is the shear stress developed at the soil-inclusion interface, is the shear stress developed at the soil-inclusion interface, s s the soil unit the soil unit
weight,
weight, P P the inclusion unit weight, the inclusion unit weight, P P the inclusion perimeter, and the inclusion perimeter, and A A p p and and A A s s the the respective cross section areas of the inclusion and the soil.
respective cross section areas of the inclusion and the soil.
The inclusion and average soil settlements are calculated by the following equations The inclusion and average soil settlements are calculated by the following equations
wherewhere E E p p is the Young’s modulus of the inclusion andis the Young’s modulus of the inclusion and E E s s the soil oedometricthe soil oedometric modulus of deformation.
modulus of deformation.
The shear stress represents for the soil-inclusion interaction which is described by a The shear stress represents for the soil-inclusion interaction which is described by a transfer function expressing the dependence of the shear stress
transfer function expressing the dependence of the shear stress τ τ with the relative with the relative
displacement between the two sub-domains
displacement between the two sub-domains p p(z) -(z) - s s(z).(z). In France, one uses widely In France, one uses widely the transfer functions proposed by Frank and Zhao 1982 [6] which are based on the transfer functions proposed by Frank and Zhao 1982 [6] which are based on Menard pressuremeter modulus
Menard pressuremeter modulus E E M M , the limit unit shaft friction, the limit unit shaft friction qq s s and end bearing and end bearing qq p p.. Such an analytical approach has been incorporated in a specific module “Taspie+” of Such an analytical approach has been incorporated in a specific module “Taspie+” of the orient
CASE STUDY CASE STUDY
Geotechnical context Geotechnical context
The numerical modeling is based on the geotechnical context of the highway The numerical modeling is based on the geotechnical context of the highway construction project Ben Luc
construction project Ben Luc – – Long Thanh in Dong Nai, Vietnam. The considered Long Thanh in Dong Nai, Vietnam. The considered section in the package A-1 from km2+090.0 to km 2+130.0 is composed two layers: section in the package A-1 from km2+090.0 to km 2+130.0 is composed two layers:
Layer 1a: this layer is fluvial sediments of Alluvial Epoch, which consists ofLayer 1a: this layer is fluvial sediments of Alluvial Epoch, which consists of very soft clay and contains organic matters sparsely.
very soft clay and contains organic matters sparsely.
Layer 2b: this layer is fluvial sediments of the latter Diluvial Epoch, whichLayer 2b: this layer is fluvial sediments of the latter Diluvial Epoch, which consists of stiff clay with some sandy considering the bearing layer.
consists of stiff clay with some sandy considering the bearing layer. A surcharge of 16kN/m
A surcharge of 16kN/m22 is setup on the embankment of 6 m of height which is is setup on the embankment of 6 m of height which is supported by the soft layer 1a. This causes probably important surface settlements supported by the soft layer 1a. This causes probably important surface settlements and stability problems. According to the Vietnamese Standards (22TCN262-2000), and stability problems. According to the Vietnamese Standards (22TCN262-2000), the settlement criteria for the considered section shall be less than 10cm. Hence, this the settlement criteria for the considered section shall be less than 10cm. Hence, this section has been reinforced by DCM columns anchored into the Layer 2b. However section has been reinforced by DCM columns anchored into the Layer 2b. However the soil reinforcement quality would be not good as expected because of the presence the soil reinforcement quality would be not good as expected because of the presence of 10% organic matters in the Layer 1a. The authors propose therefore an alternative of 10% organic matters in the Layer 1a. The authors propose therefore an alternative solution using the rigid inclusions technique. The project parameters are shown in solution using the rigid inclusions technique. The project parameters are shown in Figure 5. The effectiveness of reinforcement can be determined in terms of stress Figure 5. The effectiveness of reinforcement can be determined in terms of stress efficacy which is defined by the ratio between the load transmitted to the head of the efficacy which is defined by the ratio between the load transmitted to the head of the inclusion and the total load on the unit grid.
inclusion and the total load on the unit grid. RESULTS
RESULTS
Piled embankment behavior Piled embankment behavior
Firstly we consider the reference case consisting of 8.5m compressible soil Firstly we consider the reference case consisting of 8.5m compressible soil reinforced by 0.42m of diameter inclusions separated by a distance of 1.5m. The reinforced by 0.42m of diameter inclusions separated by a distance of 1.5m. The inclusions are 10m of depth with 1.5m of anchor in the bearing layer
inclusions are 10m of depth with 1.5m of anchor in the bearing layer – – layer 2b. The layer 2b. The mattress of 1m height is placed between the embankment and the inclusions. Figure mattress of 1m height is placed between the embankment and the inclusions. Figure 6 shows the settlement and force distribution profiles in the inclusion and in the soil. 6 shows the settlement and force distribution profiles in the inclusion and in the soil. The structure settlement is 6cm at the top embankment surface. The neutral point is The structure settlement is 6cm at the top embankment surface. The neutral point is located at 6 m of depth from the natural level where soil and inclusion settlements located at 6 m of depth from the natural level where soil and inclusion settlements are equal and where the inclusion is vertically loaded at its maximum. Obviously, at are equal and where the inclusion is vertically loaded at its maximum. Obviously, at the inclusion head level, the reinforced soil foundation is subjected to a total force of the inclusion head level, the reinforced soil foundation is subjected to a total force of 310.5kN (consisting of vehicle surcharge and the embankment and earth mattress 310.5kN (consisting of vehicle surcharge and the embankment and earth mattress weights) which is mainly transmitted to the pile (250kN), the remaining force is weights) which is mainly transmitted to the pile (250kN), the remaining force is received by the soil. The total load is then completely transmitted to the bearing layer received by the soil. The total load is then completely transmitted to the bearing layer under the inclusion.
under the inclusion.
The load transfer role of the granular earth mattress is considered by studying the The load transfer role of the granular earth mattress is considered by studying the influence of the mattress thickness in terms of the structure settlement and the stress influence of the mattress thickness in terms of the structure settlement and the stress efficacy. Figure 7 illustrates the evolutions of the two parameters versus the variation efficacy. Figure 7 illustrates the evolutions of the two parameters versus the variation of the mattress thickness between 0 to 3m, it is obvious that in range of 0 to 1m of of the mattress thickness between 0 to 3m, it is obvious that in range of 0 to 1m of
the mattress thickness (reference case) the structure settlement rapidly decreases and the mattress thickness (reference case) the structure settlement rapidly decreases and the efficacy strongly increases. After this value, they are insignificantly improved the efficacy strongly increases. After this value, they are insignificantly improved and tends to the constant values when the mattress thickness approaching to 2m. This and tends to the constant values when the mattress thickness approaching to 2m. This can be explained by the arching effect occurring within the mattress. In this case, this can be explained by the arching effect occurring within the mattress. In this case, this effect requires a necessa
effect requires a necessary thickness of 2m to be completelry thickness of 2m to be completely developed.y developed.
The influence of the inclusion diameter is then investigated, which is also based on The influence of the inclusion diameter is then investigated, which is also based on the reference case. The inclusion diameter is varied from 0.25 to 1.5m. Figure 8 the reference case. The inclusion diameter is varied from 0.25 to 1.5m. Figure 8 presents
presents the the structure structure settlement settlement evolution evolution as as a a function function of of the the inclusion inclusion diameter.diameter. The decrease of this parameter is important till a diameter of 0.5 m. After this The decrease of this parameter is important till a diameter of 0.5 m. After this diameter value, the structure settlement reaches a threshold. A possible explication is diameter value, the structure settlement reaches a threshold. A possible explication is that when the inclusion diameter is large enough, the total charge is mostly that when the inclusion diameter is large enough, the total charge is mostly transmitted to the inclusion, which leads to the fact that the inclusion and soil transmitted to the inclusion, which leads to the fact that the inclusion and soil settlements are equal and uniform over the entire depth of the inclusion.
settlements are equal and uniform over the entire depth of the inclusion. Preliminary design
Preliminary design
According to the ASIRI design guideline, the inclusion design should be verified by According to the ASIRI design guideline, the inclusion design should be verified by the following criteria:
the following criteria:
The granular earth mattress thicknessThe granular earth mattress thickness H H M M > 0.7(s-a) > 0.7(s-a) with with s s is the grid size and is the grid size and a
a the inclusion diameter. the inclusion diameter.
Prandtl’s punching failure for the mattressPrandtl’s punching failure for the mattress (Figure 9): it is convenient to (Figure 9): it is convenient to verify that the stress on the inclusion head remains below
verify that the stress on the inclusion head remains below
(( .. ))
1 1 )) 1 1 (( 1 1 0 0 M M q q q q p p N N qq H H N N q q (5)(5) wwith αith α is the coverage ratio and is the coverage ratio and N N qq= 64.2= 64.2 (for (for ’=40° ’=40° ).).
Obviously, with the reference case study H
Obviously, with the reference case study HMM = 1m > 0.7 = 1m > 0.7xx(1.5-0.36) = 0.8m and the(1.5-0.36) = 0.8m and the stress at the inclusion head is 1804 kPa less than q
stress at the inclusion head is 1804 kPa less than q p+ p+ = 1813 kPa, combined with the = 1813 kPa, combined with the estimated settlement of 6cm less than 10cm required by the Vietnamese standard. estimated settlement of 6cm less than 10cm required by the Vietnamese standard. Therefore, the authors propose this case study as a preliminary design of soil Therefore, the authors propose this case study as a preliminary design of soil reinforcement by using rigid inclusions for this highway construction project.
reinforcement by using rigid inclusions for this highway construction project. CONCLUSIONS
CONCLUSIONS
Soft soil reinforced by rigid inclusions is widely used in France. However this Soft soil reinforced by rigid inclusions is widely used in France. However this technique is not well-known in Vietnam. This work contributes to clarify the technique is not well-known in Vietnam. This work contributes to clarify the reinforcement principles by a study of the influence of the different parameters such reinforcement principles by a study of the influence of the different parameters such as the thickness of mattress layer and the cover rate on the pied-embankment as the thickness of mattress layer and the cover rate on the pied-embankment behavior based on an existing hig
behavior based on an existing highway construction project in Vietnam.hway construction project in Vietnam.
From the outcome of this work, the author proposed a design solution of soil From the outcome of this work, the author proposed a design solution of soil reinforced by rigid inclusions which is justified in accordance with the French reinforced by rigid inclusions which is justified in accordance with the French guideline ASIRI for this construction project. This would be an interesting scientific guideline ASIRI for this construction project. This would be an interesting scientific base
base for for the the application application of of rigid rigid inclusions inclusions to to future future infrastructure infrastructure constructionconstruction projects in Vietnam.
REFERENCES REFERENCES
1.
1. IREX (2012). Recommandations pour la conception, le dimensionnement,IREX (2012). Recommandations pour la conception, le dimensionnement, l’exécution et le contrôle de l’amélioration des sols de fondation par l’exécution et le contrôle de l’amélioration des sols de fondation par inclusions rigides (for the French version). Recommendations for the design, inclusions rigides (for the French version). Recommendations for the design, construction and control of rigid inclusion ground improvements (for the construction and control of rigid inclusion ground improvements (for the English version). Projet National ASIRI. Presses des Ponts, ISBN English version). Projet National ASIRI. Presses des Ponts, ISBN 978-2-85978-462-1 (available in French and English).
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by rigid rigid inclusions. inclusions. Innovative Innovative Infrastructure Infrastructure Solutions.1:27.Solutions.1:27. Doi:10.1007/s41062-016-0027-6.
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pressionmétriques de de l’enforcement l’enforcement sous sous charge charge axiale axiale des des pieux pieux forés forés dansdans les sols fins, Bulletin Liaison Laboratoire des Ponts et
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FIGURES FIGURES
FIG.1. Rigid inclusion
FIG.1. Rigid inclusion reinforcreinforcement principleement principle
Overload Overload Backfill or Backfill or Mattress Mattress Compressive Compressive soil soil Pile cap Pile cap Geotextile Geotextile Rigid Rigid inclusions inclusions Substratum Substratum
FIG.2. An displacement drilling tool. FIG.2. An displacement drilling tool.
FIG.3. Execution sequence of a
FIG.4. Model of the elementary cell around the inclusion FIG.4. Model of the elementary cell around the inclusion
FIG.5. Model parameters for soil reinforced by rigid
FIG.6. Settlement and force distributions in the
FIG.6. Settlement and force distributions in the elementary cell.elementary cell.
FIG.7. Settlement and stress efficacy evolutions with the mattress thickness. FIG.7. Settlement and stress efficacy evolutions with the mattress thickness.
FIG.8. Structure settlement as a function of
FIG.8. Structure settlement as a function of the inclusion diameter.the inclusion diameter.
FIG.9.