MRE_EN

8/18/2019 MRE_EN

1/47

MREI

© 2011 Geostru Software

MRE

Parte I Introduction 1

Parte II Working environment 1

................................................................................................................................... 41 Menu

.......................................................................................................................................................... 4File Menu

.......................................................................................................................................................... 5Edit Me nu

.......................................................................................................................................................... 5View Menu

.......................................................................................................................................................... 6Tools Menu

.......................................................................................................................................................... 7Data Menu

.......................................................................................................................................................... 7Calculation

................................................................................................................................... 82 Data

.......................................................................................................................................................... 8Model geometry

.......................................................................................................................................................... 12Building site

.......................................................................................................................................................... 14Generals

.......................................................................................................................................................... 16Geosynthetics archives

.......................................................................................................................................................... 21Soils archives

.......................................................................................................................................................... 23Conditions

.......................................................................................................................................................... 26Combinations

.......................................................................................................................................................... 28Groundwater

.......................................................................................................................................................... 30Seism

................................................................................................................................... 313 Calculation

.......................................................................................................................................................... 31Analysis options

.......................................................................................................................................................... 34Inner checks

.......................................................................................................................................................... 39Global checks

.......................................................................................................................................................... 41Project

................................................................................................................................... 424 Theoretical outline.......................................................................................................................................................... 42Calculation of the s tres s in the re inforceme nts

.......................................................................................................................................................... 45Calculation of the pullout stress

Parte III Contact 46

8/18/2019 MRE_EN

2/47

MRE1


1 Introduction

Analysis of retaining works realized with reinforced earth technology. The MRE

software allows executing both the check and the project of reinforced earth

works, duly taking into account the presence of seismic actions and the

presence of reinforcement elements inside the ground. In particular, a solution

process which takes into account the possible additional resistance offered by

the presence of the reinforcement material is organized in the software. This

latter also allows executing the classical global stability checks used in the

retaining works:

- Overturning check;

- Sliding check;

- Limit load check;

- Global stability check (Fellenius or Bishop Method).

2 Working environment

The main active window is the following::

8/18/2019 MRE_EN

3/47

Working environment 2


Figure: Main window work

From this window you can enter the basic data of the model, such as

dimensions of geometric terraces and geometric dimensions of the reinforcing

elements. The key issues relating to the window main job are:

Graphic objects:

It ispossible include graphical objects such as lines, rectangles, circles, texts

etc. These items can be used to complete the drawings required for the

preparation of a project. It's very useful the inclusion of shares by the user. In

the figure below you can see an example of use of graphical objects:

8/18/2019 MRE_EN

4/47

MRE3


Viewing surfaces sliding on the main window:

It is possible, after the various tests, see the circular sliding surfaces directly

on the main window. In particular, you can view the following groups of

surfaces:

Surfaces related t o t he analysis of global stability:

For these types of surfaces you can see all the surfaces, only the surface

a factor of at least or any surface;

Surfaces related t o t he analysis of interna l stability :

For these types of surfaces you can see all the land (these are all critical

surfaces) or any surface;

Surfaces related t o the c ompoud st ability :

For these types of surfaces you can see all the land (these are all critical

surfaces) or any surface;

8/18/2019 MRE_EN

5/47



The selection of areas to be displayed can be made using a special tool bar

(see figure below). The following figure shows a sample display of all

surfaces (Selection of 'last text box drop-down menu) for the "Combination

1" (Selection of the first text box drop) in the context of analysis of global

stability (Selection of the second text box drop-down menu).

Figure: Viewing the rupture surfaces of the main window.

2.1 Menu

2.1.1 File Menu

New

Creates file(s) for a new project.

Open:

Opens file(s) for a previously created project.

Save:

8/18/2019 MRE_EN

6/47

MRE5


Save file(s) for the currently open project, replacing any previous version.

Save As:

Save file(s) for the currently open project under the name and in the folder, to

be entered in a subsequent dialogue window. This creates a new file with thatname. If the file already exists the user is asked to confirm that it should be

overwritten.

Esc

Exit the program.

2.1.2 Edit Menu

Undo

Cancels the last amendment restoring the situation as before the change.

Copy

Copies to the clipboard the selected area of the active window. (Funct ion is

also available from the Standard toolbar). This function is particularly useful to

copy bitmaps of images in the various phases of computation to a preferred

editor (Word, Works etc.)

Paste

Pastes the clipboard in the worksheet.

Delete

Deletes the selected object in the worksheet

2.1.3 View Menu

Redraw

making the redesign of the bridle removed any errors display;

Zoom all

Allows viewing all the graphic objects present in the window, resizing the view

of the work window so that all the graphic objects can be contained;

Zoom window

8/18/2019 MRE_EN

7/47



Allows enlarging a part of the work window previously selected through a

selection box;

Move

Allows the displacement en masse (including the reference system) of thegraphic objects contained in the drawing area;

Previous Zoom

Returns to the zoom factor current before the last operation.

2.1.4 Tools Menu

Line

The use of this tool allows the interactive drawing of a line on the active

window.

Polyline

The use of this tool allows the interactive drawing of a polyline on the active

window.

Rectangle

The use of this tool allows the interact ive drawing of a rectangle on the active

window.

Circle

The use of this tool allows the interact ive drawing of a circle on the ac tive

window.

Text

The use of this tool allows the interactive insertion of a text string.

Distance

The use of this tool allows determining the distance between two points

previously selected by double clicking on the left mouse button.

Select

The use of this tool allows select ing a graphic object present in the ac tive

window. The control can only act with regard to graphic objects defined

starting from one in the previously described tools.

8/18/2019 MRE_EN

8/47

MRE7


2.1.5 Data Menu

Building site

Allows entering and changing the data relevant to the building site for the

realization of the reinforced earth work;

Generals

Allows entering and changing the general data of the work;

Geosynthetics archives

Allows entering and changing the data relevant to the Geosynthetics archives;

Soils a rchive s

Allows entering and changing the data relevant to the Soils archives;

Conditions

Allows entering and changing the data relevant to lle Load conditions;

Combinations

Allows entering and changing the data relevant to the Load combinations;

Groundwater

Allows entering and changing the data relevant to the possible Groundwater;

Seism

Allows entering and changing the data relevant to the possible Seism;

[****]

2.1.6 Calculation

Analysis Options

Allows you to insert and modify data on the options analysis;

Internal checks

Allows you to perform internal audits of the model;

Global checks

It allows to perform comprehensive audits of the model;

Project

Allows to carry out the Project of the model.

8/18/2019 MRE_EN

9/47



2.2 Data

2.2.1 Model geometry

In this data set are defined all the useful parameters for the geometrical moulding of the

model. The geometrical parameters which must be entered are relevant to:

Geo me try o f the downstream , upstream and foundation part of the non-

reinforced profile;

Ge om etry o f the reinforced soil part (reinforcem ent blocks);

Geo me try of the reinforcem ent eleme nts.

These parameters turn into the following data:

First ups trea m s tretch inclination [°] - a1m

First upstream stretch length [m] - d1m;

Second upstream stretch inclination [°] - a2m;

Second upstrea m stretch length [m] - d2m;

First downstream stretch inclination [°] - a1v;

First downstrea m stretch length [m] - d1v;

Second downstrea m stretch inclination [°] - apm;

Second downs tream stretch length [m] - d2v;

Upstream face inclination [°] - apm;

Foundation height [m] - Hf

Besides, for each reinforcing bench the following data must be defined:

Reinforcing bench he ight [m] - Hg;

Reinforcing be nch base [m] - Bg;

Do wnhill face inclination of the reinforcing be nch [°] - a .

As regards the reinforcement elements, on the contrary, the following data must be

defined:

Co ordinate of outcrop on the downhill face [m] - yr;

Total reinforceme nt length [m] - Ltot;

Reinforceme nt height [m] - Hr;

Folding leng th m] - Lr;

Geo synthetic type (to be chosen am ongst the geo synthetics defined in

the Geosynthetics archives ).

In order to enter the geometrical data correctly, it is advisable refer to the following

diagrams:

8/18/2019 MRE_EN

10/47

MRE9


Figure: Reference diagram for the definition of the model geometry

8/18/2019 MRE_EN

11/47



Figure: Reference diagram for the definition of the reinforcement geometry

The environment for the insertion of the data relevant to the geometry is the following::

8/18/2019 MRE_EN

12/47

MRE11


Figure: Environment for the insertion of the model geometrical data

Consequences of clicking on the buttons:

Apply button: Reading of the data from the form and update of the

geometrical model drawing;

? Button: Opening of the help window with regard to the data of the

model geometry.

G e ne ra te b utto n: Automatic generation of the reinforcementsthroughout the height of the reinforced work. By executing this

control you can generate a succession of reinforcements with

features equivalent to the first reinforcement defined. It follows that

the automatic generation of the reinforcements is subordinate to the

correct definition of the first reinforcement.

8/18/2019 MRE_EN

13/47



2.2.2 Building site

In this data set is defined all the necessary information to characterize the

type of the work, the project engineer and the area where the work must bebuilt – besides the standard taken as reference. The data relevant to the

building site are the following:

Date: Date of creation of the project relevant to the building site;

Project eng ineer ’ s title: The software allows choosing amongst the

following options:

Engineer;

Architect;

Surveyor;

Master contractor.

Municipality : Insertion of the name of the municipality inside which the

work will be built;

Province: Insertion of the name of the province inside which the work

will be built;

W ork des cription: Insertion of the work description;

Standard name : Insertion of the name of the standard used in the

calculation procedures;

The environment for the insertion of these data is the following:

8/18/2019 MRE_EN

14/47

MRE13


Figure: Environment for the insertion of the building site data


OK button: Recording of the data and closing of the window;

Ca ncel button: Closing of the active window without data recording;

? Button: Opening of the help window with regard to the building site data.

8/18/2019 MRE_EN

15/47



2.2.3 Generals

In this data set is defined the general information necessary for characterizing

the general behaviour of the work as well as the minimum safety requirements

of the work with regard to the different breaking modes. The general data are

the following:

Seism ic lateral pres sure :

As regards the lateral pressure from earthquakes, the programme allowsthe insertion of the coordinate corresponding to the point of application

of the action in a dimensionless form. For the determination of such

value, you can refer to the following diagram:

Figure: Diagram calculating the data relevant to the seismic lateral force.

With reference to the figure, the data to be entered is the ys quantity - Htotquantity ratio. It should be noticed that in any case the software allows not

only selecting preset values for this quantity (1/3, 2/3, 1/2) but also entering

any value.

Various properties :

Foundation adhesion:

8/18/2019 MRE_EN

16/47

MRE15


The foundation adhesion is important when the sliding check is executed on

the work. In fact, the sliding-resistant stress is evaluated through the

following formula:

a F c N Sr )tan(

Where N is the vertical foundation unloading, tan(dF) is the foundation friction

and ca is the value of the foundation adhesion.

Founda tion friction:

The foundation friction contributes to determining the sliding-resistant stress

(see previous formulas). The value to be entered in the general data window is

directly the tangent of the angle of foundation friction (tan(df)).

Soil-w ork a ngle o f friction (Soil-w ork a ngle o f friction):

This parameter determined the slope of the thrusts acting on the back of the

reinforced earth work. It must be expressed in degrees and must be higher

than 2/3 of the angle of inner friction of the thrusting soil.

Method for the calculation o f the s tability analys is:

The software allows these of two methods for the calculation of the safety

factor in the global stability analysis.

Fellenius method;

Bishop method;

Safety factors required:

Safety fac tors for the inner c hecks:

Safety factor with regard to the collapse due to the breaking of thegeneric reinforcement (reinforcement breaking);

Safety factor with regard to the collapse due to the slipping off of the

reinforcement (pullout);

Safety factor with regard to the collapse due to sliding (direct sliding).

Safety fact ors for the r igid body c hecks:

Safety factor with regard to the collapse due to the overturning of the

work;

Safety fac tor with regard to the collapse due to the sliding of the work;

Safety factor with regard to the collapse due to the limit load of the work;

Safety fac tor with regard to the collapse due to the global instability.

The environment for the insertion of the general data set is the following:

8/18/2019 MRE_EN

17/47



Figure: Environment for the insertion of the general data





2.2.4 Geosynthetics archives

In this data set are defined all the properties of the geosynthetic materials necessaryfor a correct execution of the calculation. It is possible to define, through the insertion

of new geosynthetics in the archives, how many types of geosynthetic materials you

want. For each material, the following data must be defined:

Ge neral inform ation:

Geo synthetic type:

The software allows the use of two types of geosynthetic materials:

8/18/2019 MRE_EN

18/47

MRE17


Geotextile fabrics;

Geogrids.

Geo synthetic nam e:

The name used to identify the geosynthetic in the archives must be defined.

Warning! The software does not allow the insertion of geosynthetics under the

same name;

Colour:

It refers to the colour used to graphically identify the geosynthetic material

sheet inside the active window;

Dam age factors:

The damage factors are those factors whose product constitutes the

reduction factor which allows moving on from the nominal resistance of the

geosynthetic material to the admissible resistance of the geosynthetic (T

allowable). The software allows the calculation of the admissible resistancewith different approaches, so that damage factors of different nature must be

entered according to the approached used:

Calculation according to the GR I (Ge osy nthetic Res earch Institute)

approach

According to this calculation approach, the admissible resistance is

evaluated as follows:

)( JNT BDCDCR ID

ult allow

FS FS FS FS FS

T T

Where:

FSID - Damage factor following the installation of the bound product;

FSCR - Damage factor as a consequence of the creep;

FSCD - Damage factor as a consequence of the soil chemical

aggressiveness;

FSBD - Damage factor as a consequence of the soil biological

aggressiveness;

FSJNT- Damage factor as a consequence of the superimpositions;

Calculation according to the BS8006/1995 approach (Code of prat ice for

stre ngthene d/reinforce d soils and o ther f ills).


evaluated as follows:

)( 22212211122121112111 mmmmmmm

ult allow

f f f f f f f

T T

8/18/2019 MRE_EN

19/47



Where:

fm111 - Safety fac tor on the product ion process;

fm112 - Safety factor as regards dimensional imperfections;

fm121 - Safety factor on the level of experimentation carried out;

fm122 - Safety factor on the data mining process;

fm211 - Safety factor as regards the damage in the laying stage (short-

term);

fm212 - Safety factor as regards the damage in the laying stage (long-

term);

fm22 - Safety fac tor as regards environmental factors;

Calculation according to the FHW A (Fede ral Highway Administration)

approach


evaluated as

)( CR ID D

ult allow

F F F

T T

Where:

FSD - Damage factor following the soil chemical aggressiveness;

FSID - Damage factor following the installation of the product;

FSCR - Damage factor as a consequence of the creep;

In the previous formulas, Tult is the nominal resistance of the geosynthetic material.

The environment for the insertion of the data set of the geosynthetics archives is the

following:

8/18/2019 MRE_EN

20/47

MRE19


Figure:Geosynthetic materials archives.

As regards the pullout coefficient and the direct sliding coefficient, the following

considerations are valid:

Pullout c oeff icient:

The pullout coefficient is used for the evaluation of the pullout resistance at

the geosynthetic level considered. Said coefficient is evaluated through thefollowing formula:

)tan(2

1

'

'

)tan(

)tan(

n

bb sb

S

B f

The symbols used in the previous formula have the following meaning:

as is the part of the geogrid width capable of mobilizing the passive

resistance;

8/18/2019 MRE_EN

21/47



d is the friction coeff icient between the solid part of the geogrid and the

soil;

B is the thickness of the transversal elements;

S is the distance between the transversal elements capable of mobilizingthe passive resistance.

Direc t sl iding c oeff icient:

The direct sliding coefficient is used in the check of the work direct sliding.

Said coefficient is evaluated through the following formula:

)tan(

)tan(11 sb f

The symbols have the same meaning as the previous ones. In any case, for

more clarity, please observe the following figure:

Figure: Diagram for the interpretation of the symbols used in the prev ious formulas

NB: The previous formulas are due to Jewell and are based on the

assumption of a complete interpenetration of the soil inside the open

meshes of a synthetic reinforcement element such as a geogrid.



Annulla/Cancel button: Closing of the active window without data recording;

? button: Opening of the help window with regard to the building site data;

Pull-d own te xt box: Calculation of the admissible resistance according to the

selected approach;

Right button on the left section (tree s tructure): opening of the menu for

the insertion or deletion of a geosynthetic.

8/18/2019 MRE_EN

22/47

MRE21


2.2.5 Soils archives

In this data set are defined all the soil properties necessary for a correct execution of the calculation. The software allows defining the parameters connected with three soil

categories:

Foundation s oil:

The features of the foundation soil are necessary for the execution of

the global checks, such as the limit load check and the global

instability check;

Reinforceme nt s oil:

The features of the reinforcement soil are necessary for the

execution of the inner checks and of the project of the elements

reinforcement. Obviously, said parameters are also used in the global

stability checks such as the sliding check, overturning check, limit

load check and global instability check.

Filling so il:

The features of the filling soil are necessary for the execution of the

inner checks (though the compound analysis) and of the project of

the reinforcement elements. Obviously, said parameters are also used

in the global stability checks such as the sliding check, overturning

check, limit load check and global instability check.

The identification of the parameters to be associated to the various soil blocks

can be achieved with reference to the following figure:

Figure: Schema per la definizione dei terreni

8/18/2019 MRE_EN

23/47



Diagram for the definition of the grounds

To each soil present in the archives, the following data are associated:

Specific grav ity [kN/m ³]: It is the dry soil specific gravity;

Porosity [% ]: It is the soil porosity. This parameter is necessary incase you want to calculate the saturated weight of the ground

automatically (optional calculation);

Saturated weight [kN/m ³]: It is the saturated weight of the

ground, which can be entered by the user or calculated by the

programme automatically;

Cohe sion [kN/m ²]: It is the drained cohesion of the material;

Angle of inne r friction [°]: It is the angle of inner friction of the

material;

Colour: It is the colour used to identify the soil graphically on the

act ive window.

The environment for the insertion of the data set of the soils archives is the following:

Figure: Environment for the insertion of the soils archives


OK button: Recording of the data e closing of the window;


? Button: Opening of the help window with regard to the data del building

site.

… Button: Automatic calculation of the saturated weight (the porosity value

must be entered).

8/18/2019 MRE_EN

24/47

MRE23


2.2.6 Conditions

In this data set are defined all the load conditions to which the reinforced earth

work can be subject. For each load condition, the following data must be

defined:

Condition nam e;

Set of concentrated loads contained in the condition;

Set of distributed loa ds conta ined in the condition;

NB: For a correct working of the calculation, each condition must be identified by an

unequivocal name.

As regards the loads, the software allows two types of acting loads, namely:

Concentrated loads;

Distributed load s;

The c oncentrated loads .

The concentrated loads are to be meant as punctual forces

provided with two components (one long component x and one

short component y). In order to correct ly take into account the

effects of a concentrated force, the following parameters must be

defined:

Name (Name of the concentrated load);

x [m] - Coordinate x of the force application point;

y [m] - Coordinate y of the force application point;

Fx[kN/m] – Intensity of the force in the reference direction x;

Fy[kN/m] – Intensity of the force in the reference direct ion y.

For a correct definition of the concentrated loads, it is advisable refer to the

following diagram:

8/18/2019 MRE_EN

25/47



Figure: Reference diagram for the definition of the concentrated forces

The distributed loads .

The distributed loads are to be meant as loads uniformly distributed by

length unit, determined on the basis of a unit depth. In order to correctly

take into account the effects of a concentrated force, the following

parameters must be defined:

Name (Name of the distributed load);

xInitial [m] - Coordinate x of the force application point;

xFinal [m] - Coordinate y of the force application point;

Q[kN/m] – Intensity of the distributed load value.

For a correct definition of the distributed loads, it is advisable refer to the

following diagram:

8/18/2019 MRE_EN

26/47

MRE25


Figure: Reference diagram for the definition of the distributed loads

NB: In the last figure, x0 stands for xInitial and x1 stands for xFinal.

The environment for the insertion of the data set relevant to the load conditions is the

following:

Figure: Environment for the insertion of the load conditions

8/18/2019 MRE_EN

27/47




OK Button: Recording of the data and closing of the window;



Add button: Addition of a load condition. The added condition is placed at the

end with respect to the previous conditions;

De lete button: Removal of the current condition (of the conditionwhose name

appears in the text box "Condition name").

2.2.7 Combinations

In this data set are defined all the load combinations to which the reinforced

earth work can be subject. Each load combination is, precisely, the result of

the combination of the previously defined load conditions. In case no load

condition has been defined, the software will perform the calculation taking into

consideration the default acting loads. The correct definition of a load

combination requires the insertion of the following data:

Com bination data:

Name – This is the name used to identify unequivocally the combination

inside the set of combinations;

Partial factors of the materials:

Angle of friction (gF):

This is the factor through which the tangent of the angle of friction inside

the soil is reduced:

))tan(

(tan 1 k d

Soil weight (gg):

This is the factor through which the value del weight per volume unit of the

ground is reduced:

d

Cohesion (gc):

This is the factor through which the value of the soil cohesion is reduced:

8/18/2019 MRE_EN

28/47

MRE27


c

d

cc

Admissible resistance (gR):

This is the factor through which the value of the geosynthetic admissible

strain is reduced:

Partial factors of the loads:

These are the multiplicative factors to be applied to the default

load conditions (Static action, Dynamic ac tion, Hydrostat ic ac tion,

Own weight, Upward water thrust) and to the possible load

conditions defined by the user.

Load conditions:

The user can of course choose which of the load conditionsdefined at the previous stage must be considered in the generic

load combination. In order to enter a load condition in a

combination, it is necessary to execute the following procedure:

Select the combination to which you want to add a load

condition;

Select the load condition from the upper panel of the load

conditions (red contour in the following figure)

Click on the "+>>" button.

Alternatively, it is possible to double click on the condition to be

entered from the upper panel of the conditions (red contour inthe following figure )

In order to remove a load condition from a combination, it is

necessary to execute the following procedure:

Select the combination from which you want to remove a load

condition;

Select the load condition from the lower panel of the load

conditions (green contour in the following figure)

Click on the "-

8/18/2019 MRE_EN

29/47



Figure: Environment for the insertion of the load combinations



C ancel button: Closing of the active window without data recording;


C om bination (orange background in the prev ious figure): The data relevant

to the combination are recorded.

2.2.8 Groundwater

In this data set are defined the geometrical properties of the groundwater

possibly present in the model. The correct definition of the groundwater

requires the insertion of the following data:

8/18/2019 MRE_EN

30/47

MRE29


Vertices o f the groundwate r;

For each vertex, the two coordinates of the plane – x and y, both expressed in

metres – must be defined. For a correct definition of the data relevant to the

groundwater, it is advisable to refer to the following diagram:

Figure: Diagram for the definition of the groundwater

The environment for the insertion of the data set relevant to the load conditions is the

following:

8/18/2019 MRE_EN

31/47



Figure: Environment for the insertion of the data relevant to the groundwater


OK Button: Recording of the data and closing of the window, drawing update

in the active window;



2.2.9 Seism

In this data set are defined the seismic properties of the site so as to achieve

the definition of the coefficients of the horizontal and vertical seismic thrusts.

The parameters to be entered are those provided for by the new NTC2008

regulations in force in building matters. The environment for the insertion of the

seismic data is the following:

8/18/2019 MRE_EN

32/47

MRE31


Figure: Environment for the insertion of the seismic data


Ca lculate button: This calculates the seismic parameters necessary for the

calculation (Kh, Kv);


? Button: Opening of the help window with regard to the building site data;

Ge ostru PS button: Opening of the Webpage "www.geostru.com/geoapp" for

the on-line calculation of the seismic parameters;

Im port from Ge ostru PS button: Reading of the text file generated on the

Website www.geostru.com.

2.3 Calculation

2.3.1 Analysis options

In this data set are defined the analysis parameters (e.g. the variation range of

the radius for the circular sliding surfaces). The parameters must be defined for

the following types of analysis:

Global sta bility analys is;

Inner s tability a nalysis (aimed at determining the critical surfaces which are

completely contained in the reinforcement soil portion);

Com pound stability analysis (aimed at determining the critical surfaces

possibly extending outside the reinforcement soil area, and consequently being

deeper than those calculated through the previous analysis);

In any case, the following parameters must be defined for all three types of analysis:

Coordinates x and y of the initial analysis point;

8/18/2019 MRE_EN

33/47



Coordinates x and y of the final analysis point;

Coordinates x of the second point of the circular sector, under starting

analysis conditions;

Coordinates x of the first point of the circular sector, under final analysisconditions;

Surfaces research step. This is measured according to the curvilinear

abscissa which crosses the ground profile;

Minimum radius. This is the minimum radius of analysis;

Maximum radius. This is the maximum radius of analysis;

Radius step. This is the increase in the radius value.

NB: Clicking on the "Calcola parametri"/"Calculate parameters" button,

the programme will set the values of the above-mentioned

parameters automatically. When necessary, the user can proceed to

the change starting from the automatically calculated estimate.

In any case, for a correct definition of the analysis parameters it is advisable to refer to

the following diagram:

Figure: Reference diagram for the identification of the first 5 analysis parameters

8/18/2019 MRE_EN

34/47

MRE33


Figure: Reference diagram for the identification of the last 3 analysis parameters

NB: What is defined above as the Radius Rate is the step to be used in movingon from the minimum radius to the maximum radius. The environment for the

insertion of the data set relevant to the analysis options is the following:

8/18/2019 MRE_EN

35/47



Figure: Environment for the insertion of the analysis options


OK Button: Recording of the data and closing of the window, update

of the drawing in the active window;


? Button: Opening of the help window with regard to the data del

building site;

Calculate parameters button: Automatic calculation of the analysis

parameters (it is advisable always to start from the automatically

calculated data).

2.3.2 Inner checks

The inner checks are aimed at determining the safety factor with regard to the following

collapse phenomena:

Reinforceme nt breaking;

Re inforcem ent s lipping off (pullout).

In the following figure are shown the diagrams of the collapse mechanisms it is

possible to analyze by means of the inner stability analysis.

8/18/2019 MRE_EN

36/47

MRE35


Figure: Local collapse mechanisms (Inner stability analysis)

One of the essential steps in the check calculation of a work is to calculate the

stress occurring in the reinforcements. The flow chart of the algorithm used for

this purpose is the following:

8/18/2019 MRE_EN

37/47



Figure: Flow chart for calculating the stress in the reinforcements.

In the previous figure, r is the index which identifies the reinforcement (the

numbering ranges from the highest reinforcement (r=1) to the lowest

reinforcement (r=nr)). After the calculation of the stress in the reinforcements,

a check must be carried out as well.

NB: The calculation of the stress in the reinforcement is performed on the

side of the flow chart (red boxed in the previous figure) where the unit

(FS(Tr)-1=0) safety factor (calculated according to Tr, which is the

stress searched for) is assumed. The solution to the equation can be

found through a classical method of numerical solution (Newton’s

method aka Method of secants).

Reinforceme nt brea king check:

8/18/2019 MRE_EN

38/47

MRE37


This check consists in satisfying the following ratio:

rr

r

Rallowrc

FS T

T FS

)/(

Where the meaning of the symbols (which is the one defined in the previous

sections) is the following:

Tr is the stress calculated in the reinforcements (with the algorithm

concerned by the previous figure);

Tallow is the admissible (allowable) stress of the r-th geosynthetic;

gR is the partial combination factor to be applied to the resistances;

FSrc is the calculated safety factor, with regard to the breaking of the

reinforcement;

FSrr is the required safety factor, with regard to the breaking of the

reinforcement.

Slipping o ff check (Pullout che ck):

This check consists in satisfying the following ratio:

pr

r

R p

pc FS T

T FS

)/(

Where the meaning of the symbols (which is the one defined in the previous

sections) is the following:

Tr is the stress calculated in the reinforcements (with the

algorithm concerned by the previous figure);

Tp is the pullout-resistant stress (depending on various factors

including the reinforcement normal strain, the soil-geosynthetic

interface friction coefficient, etc.) relevant to the r-th

geosynthetic;

gR is the partial combination fac tor to be applied to the

resistances;

FSpc is the calculated safety factor, with regard to the breaking

by slipping off (pullout-related breaking);

FSpr is the required safety factor, with regard to the breaking by

slipping off (pullout-related breaking).

The environment for above-mentioned checks is the following:

8/18/2019 MRE_EN

39/47



Figure: Environment for the output display

8/18/2019 MRE_EN

40/47

MRE39


2.3.3 Global checks

In the framework of the present software, by global checks we mean the ones relevant

to the collapse with regard to:

Overturning of the whole work considered as a rigid body;

Sliding of the whole work on the surface of contact with the foundation (the

work is always considered as a rigid body);

Limit loa d of the work foundation;

Slippage of work portions with the sliding plane coinciding with the soil-

geosynthetic interface.

Overturning check

The overturning check consists in comparing the extent of the overturning

moments with the stabilizing moments. The reference pole for the calculation of the moments coincides with the reference system which regard to which the

forces are defined (as shown in the following figure):

Figure: Diagram for the calculation of the overturning moments and stabilizing moments

With regard to the previous figure and to the reference diagram for the

8/18/2019 MRE_EN

41/47



definition of the forces, the different forces will generate an overturning

moment if the product between F(i) and dF is higher than 0 (zero), otherwise it

will generate a stabilizing moment. In any case, the ratio to be satisfied in

order to consider the overturning check as positive is the following:

rr rc FS MR

MS FS

Please refer to following meaning of the symbols:

FSrc is the calculated overturning safety factor;

FSrr is the required overturning safety factor;

MS is the stabilizing moment;

MR is the overturning moment.

The software, besides considering the loads defined by the user in theframework of the load conditions and combinations, also considers the

following loads (set by default):

Static thrust of the ground on the back of the work;

Dynamic thrust of the ground on the back of the work;

Hydrostat ic thrust;

Upward water hydrostatic thrust;

Weight characteristic of the reinforced mass.

Sliding che ck:

The sliding check consists in comparing the extent of the resultant of

the sliding-soliciting forces with the extent of the resultant of the

sliding-resistant forces (mainly by friction and adhesion). The diagram

to be taken as reference is the one reported in the previous figure. In

any case, the ratio to be satisfied in order to consider the sliding

check as positive is the following:

sr

sol

res sc FS

F

F FS


FSsc is the calculated overturning safety factor;

FSsr is the required overturning safety factor;

Fres is the sliding-resistant force;

Fres is the sliding-soliciting force.

Ca pacity bea ring check:

The capacity bearing check consists in comparing the extent of the

maximum operating strain under the foundation with the extent of the

8/18/2019 MRE_EN

42/47

MRE41


limit breaking strain of the work-foundation ground complex. The ratio

to be satisfied in order to consider the limit load check as positive is

the following:

r q

es

ucq FS Q

Q FS limlim


FSqlimc is the calculated limit load safety factor;

FSqlimr is the required limit load safety factor;

Qu is the collapse limit load of the work-foundation complex;

Qes is the calculated operating strain.

2.3.4 Project

In the framework of the present software, it is possible to realize the project of

the reinforced earth work. In particular, you are allowed to execute the

calculation of the following quantities:

Ca lculation of the s pacing betwee n the reinforceme nts once the

ultimate calculation strain of the ge osy nthetic has bee n fixed;

Ca lculation o f the ultim ate calculation strain of the geos ynthetic

once the spa cing betwee n the reinforcem ents has bee n fixed.

It is possible to fix the spacing between the reinforcements or to fix the

ultimate calculation strain of the geosynthetic. The calculation strain of the

geosynthetic material can be fixed arbitrarily, i.e. choosing amongst the strains

corresponding to the geosynthetics present in the archives (double clicking on

the geosynthetics list on the left of the window). It is also possible to choose

the minimum amongst the calculation st rains corresponding to the

geosynthetics present in the archives (c licking on the button with three dots

(...)).


Ca lculation button: Execution of the check calculation;

Close button: Closing of the active window;

? Button: Opening of the help window with regard to the building site data;

[… ] Button: Loading of the minimum calculation strain as regards the

geosynthetics present in the archives.

8/18/2019 MRE_EN

43/47



2.4 Theoretical outline

2.4.1 Calculation of the stress in the reinforcements

The calculation of the tensile force in the reinforcements is performed using a

variant to Leshchinsky’s algorithm. Actually, it being understood that the basic

concept is valid, in the present application a circular sliding surface – different

from the one used in Leshchinsky’s method, which belongs to the logarithmic

spiral type – is used. The algorithm used is aimed at detecting - for each

reinforcement level – the critical surface, i.e. that surface in whose

correspondence the maximum strain occurs in the reinforcement, imposing a

unit safety factor. A schematic representation of the used algorithm (which

has already been presented above) is shown in the following figure

8/18/2019 MRE_EN

44/47

MRE43


Figure: Flow chart for calculating the stress in the reinforcements

As it can be easily observed, the algorithm provides that – for each point of

outcrop (and so for each r in the previous figure) – amongst all the possible

circular surfaces, the surface to which the maximum resistance value required

from the geosynthetic is selected, so as to stabilize the ground portion

overhanging it (by means of a safety factor equal to 1). Basically, it isnecessary to search for the maximum tn value for each equation of the unit

safety factor. In the following figure is shown once again a schematization of

the procedure:

8/18/2019 MRE_EN

45/47



Figure: Schematization of the algorithm for the calculation of the stress in thereinforcements

Schematization of the algorithm for the calculation of the stress in the

reinforcements

1:0 Mr

Ms FS Ms Mr

Where Mr is the overturning moment and Ms is the stabilizing moment. As it

can be observed, the critical surface is such that the moment equilibrium

condition is checked under conditions of an incipient breaking (FS=1).

NB: The calculation of the stress in the reinforcement is performed on

the side of the flow chart (red boxed in the previous figure) where the

unit (FS(Tr)-1=0) safety factor (calculated according to Tr, which is the

stress searched for) is assumed. The solution to the equation can be

found through a classical method of numerical solution (Newton’s

method aka Method of secants).

8/18/2019 MRE_EN

46/47

MRE45


2.4.2 Calculation of the pullout stress

The pullout stress defines the extent of the limit stress to which the generic

geosynthetic can be submitted without the slipping off (pullout) phenomenon

occurring. The formula used to calculate the pullout stress is the following:

)tan(2 bnr r b f W LT

Where the symbols have the following meaning:

Lr is the length of the reinforcement section anchored in the stable ground

portion;

Wr is the width of the geosynthetic at the considered level;

sn is the effective reinforcement normal strain at the considered level;

fb is the pullout coefficient, for whose definition please refer to the

Geosynthetics archives sec tion;

f is the angle of inner friction of the ground situated in direct contact with

the reinforcement;

For more clarity, it is advisable to refer to the following figure:

Figure

8/18/2019 MRE_EN

47/47


Figure

3 Contact

GeoStru SoftwareSkype Nick: geostru_support_it-eng-spa

Web: www.geostru.com

E-mail: [email protected]
mailto:[email protected]://www.geostru.com/

Documents

MRE_EN