WO2017176232A2

WO2017176232A2 - A mechanism and method to reduce the stresses acting on the buried - flexible pipes

Info

Publication number: WO2017176232A2
Application number: PCT/TR2017/050132
Authority: WO
Inventors: Havvanur KILIC
Original assignee: Kilic Havvanur
Priority date: 2016-04-04
Filing date: 2017-04-04
Publication date: 2017-10-12
Also published as: WO2017176232A3

Abstract

The invention (lOO) relates to a mechanism and a method for reducing or preventing the stresses acting on buried flexible pipes which are subjected to deformation under loading caused by earthfill (GEB) by using compressible fill material (DM) with different thickness and with the schemes of placement suggested by this invention and covers to increase the mechanism of positive arching which causes the decrease or the prevention of the deformation to which flexible pipes are subjected reduce or prevent stresses acting on buried flexible pipes (GEB) that increases the phenomenon of positive arching (PK),most importantly, irrespective of the deformation of the pipe (GEB).

Description

A MECHANISM and METHOD to REDUCE THE STRESSES ACTING ON THE

BURIED - FLEXIBLE PIPES The Technical Area of the Invention:

The invention is a mechanism and method to reduce the stresses which will be transmitted to a buried-flexible pipe.

Prior Art

The buried flexible pipes are actually considered to be infrastructural elements which may be deformed under loading (High Density Polyethylene, HDPE) and this property that they have causes a positive arching mechanism, leading to differential settlement of a soil medium within which they are present. However, it is also clear that a buried-flexible pipe is required to be subjected to a least possible deformation during its service period.

The process of the design and insertion of a buried pipe is carried out according to the instructions stated by AASHTO (Section 30), CAN/CSA B 182. i l and ASTM D 2321-14el. A typical cross section for a typical buried pipe is shown in the Figurel. As seen in this figure, flexible pipe is placed on a bed layer lying on the foundation soil (e.g., a backfilling material which will be used along the perimeter of the pipe) and both the two sides and the top surface of the pipe is then backfilled respectively.

For a designer, it is a very critical importance to control both vertical and horizontal earth pressures on economizing on the design of pipes and to reduce the stresses acting on pipes in order to restrict the deformations to which pipes may be subjected. Therefore, the loads transmitted by pipes of low rigidity will be carried safer and more economically.

For the technique in use, another application is shown in Fig 2. The condition in which the crown of the pipe exhibits much settlement compared to the critical plane is referred to as the trench condition. In other words, if the flexible pipe is deformed in the vertical direction and positive arching occurs, this condition is called the trench condition. A flexible pipe for that condition is shown in Figure 2. The first position of the pipe, critical plane and equivelant level of settlement are marked by the dotted lines. Positive arching has occured in accordance with the decrease in the vertical length of flexible crown of the pipe (d_c) under the effect of the weight of the unit area of the fill material (W). As seen in Figure 2, positive arching has took place on the sides of the prisms of soil on the pipe as the result of the development of the upward-arrows.

In this application (Fig.2), the settlement of the crown of the flexible pipe is the sum of the settlement of the foundation soil beneath the flexible pipe (Sf) + the amount of decrease in the vertical length of the crown of the pipe (d_c). The total settlement of the backfill material placed on the sides is equal to the sum of the settlement of the prism of soil caused by sidefilling of the pipe (s_m) and that of the natural soil on the sides of the pipe (s_g). Since the value of (Sf+d_c) is greater than (s_m+s_g), positive arching occurs and the weight of the unit area of the soil on the pipe (W) is less than the load caused by the prism (γΗ). In case of flexible-pipes, the load acting on the pipe decreases by a small amount due to positive arching and so the value of W becomes less than (γΗ).

As seen from this figure, positive arching occurs depending on the decrease in the length of the crown of the pipe. If the decrease in length increases, then the deformations that the pipe goes through will increase; and as a result the flexible pipe may be deformed excessively and will be subjected to too damage to function.

The Brief Description of the Invention:

The main objective of the invention is to reduce both the vertical stresses and horizontal stresses acting on the pipe and to prevent the pipe from being deformed if it is possible and if not, to keep the deformations at a minimum.

This objective, by the new invention, is achieved by placing the compressible fill material in accordance with the appropriate scheme of placement. The invention prevents excessive deformations to which the pipe will be subjected due the positive arching occuring in the medium, irrespective of the deformation of the pipe. In other words, irrespective of the deformation of the pipe, positive arching is developed by the effect of compressible fill material.

In this invention, after the foundation soil is prepared at the place that the pipe is put in accordance with the standarts, compressible fill material is placed on the crown and/or under the invert of the pipe in the form of plates or in the form of semi-saddle or saddle; the the both sides and the top and of the pipe is then backfilled layer by layer under carefully controlled way and the process of the placement of the pipe is completed. Therefore compressible fill material is subjected to deformation under the applied load and so the stresses acting on the pipe are reduced due the development of the positive arching, leading to the decrease in the deformation of the pipe. In other words, compressible fill material will increase positive arching mechanism irrespective of the deformation of the flexible pipe and cause the stresses acting on the pipe to reduce. If the compressible layer are used for flexible pipes in accordance with the mechanism and method imposed by the invention proposed in this instruction, the stresses on the pipe will be transfered to the filling material on the side of the pipes. The decrease or the prevention of the stresses acting on the pipe will have the effect on decreasing deformations to which the pipe will be subjected.

In other words, the increase in the phenomenon of arching, irrespective of the deformation of the pipe, is achieved by means of the mechanism and method imposed by the invention proposed in this instruction. If the compressible fill material is placed on flexible pipes in accordance with the mechanism and method imposed by the invention proposed in this instruction, irrespective of deformations of the pipe, the arching effect will increase and the stresses acting on the pipe will decrease.

Detailed Description of the Invention:

Description of Figures Figure 1: The procedure of burying of flexible pipe for the trench condition (ASTM 2321) in case of the prior art

Figure 2: It is the schematic appearence of the development of arching mechanism for a flexible pipe in case of the prior art

Figure 3. It is the schematic appearence of the development of arching mechanism for a flexible pipe in case of using compressible arching mechanism in accordance with the invention.

Figure 4. The schematic appearence of installation of the compressible fill material (DM) on the crown of the flexible pipe in accordance with the invention (placement # 1).

Figure 5: The schematic appearence of installation of the compressible fill material (DM) that is placed in the form of a plate under the invert of flexible pipe in accordance with the invention (placement # 2).

Figure 6: The schematic appearence of installation of compressible fill material(DM) which is placed in the form of a plates on the crown and under the invert of flexible pipe in accordance with the invention (placement # 3 a)

Figure 7: The schematic appearence of installation of compressible fill material which is placed in the form of semi- saddle on the crown and under the invert of flexible pipe in accordance with the invention (placement # 3b)

Figure 8: The schematic appearence of installation of compressible fill material(DM) which is placed in the form of saddle on the crown and under the invert of flexible pipe in accordance with the invention (placement # 3c)

Figure 9: The schematic appearence of burying of the flexible pipe in case of using compressible fill material(DM) in the form of saddle on the crown and under the invert of the flexible pipe in accordance with the invention (placement # 3c)

Figure 10: Flow diagram of the method for burying of flexible pipe in placement # 1.

Figure 11: Flow diagram of the method for burying of flexible pipe in placement # 2.

Figure 12: Flow diagram of the method for burying of flexible pipe in placement # 3a.

Figure 13: Flow diagram of the method for burying of flexible pipe in placement # 3b.

Figure 14: Flow diagram of the method for burying of flexible pipe in placement # 3c. Explanation of the references in the figures: For the comprehension of the invention, the parts in the figures are numbered individually and the counterparts of these numbers are given below.

GEB: Buried Flexible Pipe

TA: Pipe Crown

BT: Pipe Invert

YAD: Side-Wall of the Pipe

DSC: Vertical Symmetrical Line

YSC: Horizontal Symmetrical Line

DD: Fill Level

DZ: Backfill (from AASHTO M145)

D: Pipe Diameter

YK: Bed Thickness

T: Foundation

YD: Sidefill (from AASHTO M145)

L: EPS Material Thickness

DM: Compressible Material

H: Distance Between Fill Level and Crown Level

D(min): The outer diameter of the pipe

D/10: Length up to 1 / 10th of pipe diameter

KD: Critical Plane

FP: The first Position of the Flexible Pipe

EOD: Plane of Equal Settlement

PK: Positive Arching

s_m : Settlement of Soil at Sides of Pipe

s_g : Settlement of natural ground surface at sides of pipe s_f Settlement of foundation bottom of the pipe

s_d : Compression of Compressible Fill Material

d_c : Deflection of the Top of Pipe

γ : Unit Weight of Backfill

H : Height of Fill Above Top of Flexible Pipe (Distance Between Critical Plane and Fill Level) W: Weight of Unit Area of the Fill Above the Pipe When Compressible Fill Material is not used

W': Weight of Unit Area of the Fill Above the Pipe When Compressible Fill Material is used

(Sf+d_c): Total Settlement of the Crown of the Flexible Pipe(TA)

(s_m+s_g): Total Settlement of the Sidefill of Pipe

(Sf+d_c+Sd): The sum of the settlement of compressible fill material (s ) and total settlement of the crown of the flexible pipe(s_f+d_c) in case of placement of the compressible fill material(DM) on flexible pipe

Buried flexible pipes(GEB) can not be utilized as they could not bear high stresses acting on them(GEB) without being deformed. In accordance with the method of the invention(lOO), excessive deformation of the buried flexible pipe(GEB) is prevented by reducing the stresses acting on them (GEB) using the appropriate scheme of placement of the compressible fill material(DM).

In the preferred application of the invention, high density polyethylene (HDPE) pipes are used as a flexible pipe(GEB). In other applications of the invention, Polyvinyl Chloride Pipes (PVC), Steel Reinforced High Density Polyethylene Pipes (SRHDPE), Polypropylene flexible pipes can be used as the flexible pipe (GEB).

In the method of the invention (100); after the foundation soil(T) is prepared in accordance with the standards at the place that the flexible pipe(GEB) will be put in, compressible fill material(DM) is installed in the appropriate scheme of the placement and the both sides(YAD) and crown(TA) of the flexible pipe(GEB) is then backfilled(DZ) layer by layer and the process of the placement of the pipe(GEB) is completed. Subsequently, the compressible fill material(DM) will be subjected to deformation under the applied load that is irrespective of the deformations of the pipe(GEB), the positive arching(PK) rate will increase and the stresses acting on the pipe(GEB) will decrease. It is suggested to use Expanded Polystyrene (EPS) Geofoam material as a compressible fill material(DM) in both method(lOO) and mechanism for the preferred application of the invention. Positive Arching(PK) Mechanism for Buried Flexible Pipe

A typical flexible pipe(GEB) which is placed in trench condition in the invention is shown in Figure 3. The initial position(FP) of the pipe(GEB), the critical plane(KD) and the equivalent settlement plane(EOA) are indicated by dashed lines. As a result of the positive arching, some part of the load acting on the pipe is transferred to the sidefill(YD). Thus, the vertical displacement in the crown of flexible pipe is reduced to a minimum or zero.

In case of the placement of a compressible fill material (DM) on the flexible pipe as seen in Fig.3 the compression of compressible fill(Sd) material(DM) will be added to the settlement of the pipe crown(Sf+d_c),(Sf+d_c+Sd) in total, and since the value of(Sf+d_c+Sd) is greater than(Sf+d_c), the weight of the unit area of the soil on flexible pipe(W') would be less thanW. Thus, the compressible fill material(DM) will be subjected to a certain amount of deformation under the applied load, irrespective of deformations of the pipe(GEB), and the positive arching(PK) rate will increase and the stresses acting on the pipe crown(TA) will decrease.

If the weights acting on a unit area of soil for a flexible pipe condition are compared for both the invention as seen in Fig 3 and the prior art shown in Fig 2, it is seen that W is greater than W and depending on that situation it is concluded that the deformation of the flexible pipe is reduced. If expected amount of positive arching(PK) occurs as a result of increasing of the upward arrows of the edges of the soil prism shown in Figure 3 the stresses acting on the flexible pipe(GEB) and the deformation of the flexible pipe(GEB) will be able to reduce considerably. The mechanism proposed by the invention (or by the suggested approach) reduces or prevents the deflection of the flexible pipe(GEB) by reducing the vertical and horizontal stresses acting on the pipe(GEB). In this approach, the compressible fill material(DM) with a predetermined thickness is placed on the crown and/or under the invert of the flexible pipe(GEB) so as to increase the positive arching which ensures that load is partially or totally transfered to side fills of the buried pipe instead of the pipe. By the suggested approach, the compressible fill material(DM) is placed either in the form of plate over the pipe crown(TA) and under its invert(BT) or in the form of semi-saddle or in the form of saddle on the crown(TA) and under the invert(BT) of the flexible pipe. In addition to these applications, the compressible fill material(DM) may be placed either just on the flexible pipe crown(TA) or just under the invert(BT) of the flexible pipe in form of plate.

In applications, the compressible fill material is placed in such a way as to contact or not to contact to the pipe(GEB). In addition, the compressible fill material(DM) is placed as a at least one layer. In the preferred application of the suggested approach that the compressible fill material(DM) is placed as a single layer.

In all applications of the invention, the compressible fill material(DM) is placed in such a way as to contact or not to contact to the flexible pipe(GEB). Afterwards, the application is completed by the process of backfilling(DZ) over the flexible pipe(GEB) and the compressible fill material(DM). The materials recommended in AASHTO M145 soil classification can be use as a backfill material(DZ) in applications in which a compressible fill material(DM) is to be placed.

According to the method of the invention, compressible fill material(DM) is placed under the invert(BT) and/or crown(TA) and/or on the side walls(YAD) of the pipe. Thus, the behavior of the pipe and its surrounding soil can be examined. By the suggested approach, particularly in the preferred applications, five different alternatives as the scheme of placement can be used, which are placement #1, placement #2, placement #3a, placement #3b, placement #3c respectively. Furthermore, compressible fill material(DM) used in particularly the preferred applications has densitiyies of 10 or 15 kg/m . However, compressible fill materials(DM) with different density may also be used in applications. In this method(lOO), the buried flexible pipe(GEB) is allowed to deflect together with compressible fill material(DM) without being exposed to excessive deflection under vertical load, and the positive arching(PK) mechanism develops at the highest level due to the relative vertical displacement occured at the pipe crown(TA). The schemes of placement of compressible fill material(DM) proposed by the suggested approach(lOO) are given in Fig. 4, Fig. 5, Fig. 6, Fig.7 and Fig 8 respectively.

By the suggested approach(lOO), the behavior of the buried flexible pipes(GEB) and its surrounding soil under high earth fill loads can be controlled by using a compressible fill material(DM).

In this invention(lOO), compressible fill material(DM) is placed on the crown and/or under the bottom of the pipe, and it is thereby ensured that the increasing in relative settlement occured at the crown(TA) and/or under the bottom(BT) of the pipe contributes to positive arching(PK). Thus, vertical and horizontal stresses acting on the pipe(GEB) are reduced. In the application of the compressible fill material(DM) crown(TA)(Fig-4) is placed either so as to contact or not to contact with the top of the flexible pipe(GEB) crown of the, which is similar to imperfect trench method used for rigid pipes. In another application of the invention(lOO), compressible fill material(DM) is placed in the form of plate under the bottom(BT) of the pipe either so as to contact or not to contact with the invert of the flexible pipe(GEB), which is termed an invert application for the compressible fill material(Figure-5). In another applications of the invention(lOO), compressible fill material(DM) is placed in the form of plate both at the top and bottom of the pipe(GEB) so as to contact or not to contact with the the crown(TA) and the invert(BT) of the flexible pipe (Fig. 6, 7, 8). This kind of application is a crown and invert application for the compressible fill material. In different applications of the invention, compressible fill material of different geometry are used instead of plate-shaped ones. According to the invention(lOO), compressible fill material(DM) is suggested to be placed in the form of plate on crown of flexible pipe(TA) as shown in Figure 4 (placement #1), under the invert of flexible pipe(BT) as shown in Figure 5 (placement #2), and on both of the crown(TA) and under the invert(BT) of the pipe as shown in Figure 6, 7 and 8 (placement #3a, 3b, 3c). In another application suggested in the invention in addition to these placements, a second layer of compressible fill material(DM) could be placed above the the crown of pipe in the form of plate.

In placement #3a, a plate shaped compressible fill material(DM) is placed in both at the top and the bottom of the pipe so as to contact or not to contact with the flexible pipe(GEB) (Figure 6), in placement #3b, a semi saddle shaped compressible fill material is used (Fig. 7) and in placement #3c, a saddle shaped compressible fill material is used (Fig. 8) so as to contact or not to contact with the flexible pipe(GEB). In the preferred application of the invention, when the compressible fill material(DM) is placed under the invert of the pipe(GEB) from the bottom of the flexible pipe(GEB) and/or on the crown in the form of plate as shown in Fig. 4, Fig. 5 and Fig. 6, the width and the thickness(L) of the compressible fill material(DM) can be predetermined. To do so it is suggested by the new approach that its width is up to the outer diameter of the flexible pipe (D), and its thickness is up to 1/6 of the pipe diameter, that is, L = 1/6D or at least is equal to 5 cm. However, different applications is possible to use fill material of different thickness. When the compressible fill material(DM) is placed on the crown and under the invert of the flexible pipe(GEB) in semi-saddle or saddle form (Figures 7 and 8), it is suggested by the new approach that the width of the compressible fill material(GEB) should be enlarged by a certain amount of the outer diameter of the flexible pipe (D), (e.g. both the right and left sides of the flexible pipe, one-tenth of the diameter of the flexible pipe, that is, D/10) (Figure 9).

A compressible fill material(DM) whose width is equal to the diameter of the pipe(GEB) is used in the diameter of the pipe in the preferred application of the invention . However, compressible fill material(DM) of different diameter which are properly larger than the diameter of the pipe can be used in other applications of the invention.

By means of the method of the invention(lOO), after preparing the foundation(T) soil in accordance with the standards where the flexible pipe(GEB) will be buried,

- if the compressible fill material(DM) is placed so as to contact or not to contact with the crown and/or under the invert of the flexible pipe(GEB) in the form of plate or in the form of semi- saddle or saddle, and

- if the process of burying of the flexible pipe(GEB) are completed by filling both the sides and the top of the flexible pipe with the backfill(DZ) specified in for example AASHTO M145 under a carefully controlled manner;

- since the rigidity of the compressible fill material(DM) positioning to the flexible pipe is very low compared to the rigidity of the side fill(YD) material of the flexible pipe, the soil prism on top of the pipe(GEB) will settle much more than the side soil prisms,

- After that, the resultant force, caused by the upward resisting forces which are developed against shear along the interface between the mass of soil on the flexible pipe(GEB) and side-fill(YD) material and the forces by lateral earth pressure, will cause a belt structure to take place within soil mass.

- Furthermore, an arching mechanism will be developed irrespective of the vertical deflection of the flexible pipe (GEB) by this process which will cause the load to be transmitted from the soil mass that will settle to the side-fill(YD) that remains static.

In the application carried out in accordance with the suggested approach(lOO), when the compressible fill material(DM) is placed on the crown of the flexible pipe the steps to be followed are (Figure 4):

- Preparation of the foundation(T) soil in accordance with the standards(lOla)

- Placement of flexible pipe(GEB) on the foundation(T) soil(102a)

- Filling the sides(YAD) of the flexible pipe(GEB) up to top of the pipe(GEB) with an appropriate backfill material(DZ) in a controlled manner(103a) - Placement of compressible fill material(DM) in the form of plate (104a)

- Filling the top of the compressible material fill(DM) with an appropriate backfill material(DZ) in a controlled manner (105 a)

The another application of this invention(lOO) is to place the compressible fill material(DM) invert(BT) from bottom of the pipe as a plate by following the below steps(Figure 5):

- Preparation of the foundation(T) soil in accordance with the standards(lOlb)

- Placement of compressible fill material(DM) on the foundation(T) soil in the form of plate(102b)

- Placement of flexible pipe(GEB) on the compressible fill material(DM)(103b) - Filling first the sides of the flexible pipe(GEB) and then the top of the pipe with an appropriate backfill material(DZ) in a controlled manner (104b)

The other application with this invention is to place the compressible fill material(DM) invert(BT) from bottom of the pipe and to place the material on top of the pipe crown(TA) as a plate by following the below steps(Figure 6):

- Preparation of the foundation(T) soil in accordance with the standards(lOlc)

- Placement of compressible fill material(DM) on the foundation(T) soil in the form of plate(102c).

- Placement of flexible pipe(GEB) on the compressible fill material(DM)(103c).

- Filling the sides(YAD) of the flexible pipe(GEB) up to the top of the pipe with backfill(DZ) in a controlled manner(104c)

- Placement of compressible fill material(DM) in the form of plate on the flexible pipe(GEB)(105c)

- Filling the sides and top of the compressible fill material (DM) with an appropriate backfill material(DZ) in a controlled manner(106c)

In another application of the the invention, when the compressible material in the form of semi-saddle is placed under the flexible invert of pipe beneath the bottom of the pipe and on the crown of the pipe, the steps to be followed are (Figure 7):

- Preparation of the foundation(T) soil in accordance with the standards(lOld)

- Placement of compressible fill material(DM) on the foundation(T) soil in the form of a semi saddle(102d) - Placement of flexible pipe(GEB) on the compressible fill material(DM) in the form of semi saddle(103d).

- Filling the sides(YAD) of the flexible pipe(GEB) up to the horizontal symetrical line (YSC) with an apropriate backfill material(DZ) in a controlled manner(104d) - Placement of compressible fill material(DM) in the form of semi saddle on the crown(TA) of flexible pipe(GEB)

- Filling the sides and top of the compressible fill material(DM) in the form of semi saddle with an appropriate backfill material(DZ) in a controlled manner (106d) The other application with this invention(lOO) is to place the compressible fill material(DM) invert(BT) from bottom of the pipe and to place the material on top of the pipe crown(TA) as saddle geometry by following the below steps(Figure 8):

- Preparation of the foundation(T) soil in accordance with the standards(lOle)

- Placement of compressible fill material(DM) on the foundation(T) soil in the form of a saddle(102e)

- Placement of flexible pipe(GEB) on the compressible fill material(DM) in the form of saddle(103e).

- Placement on top of flexible pipe(GEB) of the compressible fill material(DM) in the form of saddle(104e)

- Filling the sides and top of the compressible fill material(DM) in the form of semi saddle with an appropriate backfill material(DZ) in a controlled manner(105e)

Flow diagrams of the burying of flexible pipes(GEB) for each placement arrangement are shown in Figures 10, 11, 12, 13 and 14.

The design of buried pipes(GEB) varies with the rigidity of the pipe(GEB) and the soil and the resulting pipe-soil interaction. For the proposed application, factors such as the density of the compressible fill material(DM), the thickness, the arrangement of the placement, the type of flexible pipe(GEB), the type of backfill(DZ) affect this interaction.

The industrial applicability of the invention

Claims

1. A mechanism which is characterized by using compressible fill material(DM) of certain desired thickness which is placed under the invert(BT) of the buried flexible pipe(GEB) and/or on the crown(TA) of the buried flexible pipe and/or sidewalls(YAD) of the buried flexible pipe to reduce or to eliminate completely the deformations to which pipe(GEB) will be subjected causing vertical and horizontal stresses acting on pipes to reduce due to positive arching(PK) which enables that loads are transfered to sidefills(YD), instead of directly pipes(GEB).

A mechanism as described in claim 1, which is the compressible fill material (DM) is placed in the form of plate on the crown(TA) of the flexible pipe and under the invert(BT) of the pipe.

2. A mechanism as in claim 1, wherein the compressible fill material(DM) is placed on the flexible pipe crown(TA) and/or to the invert(BT) of the pipe from underneath in the form of semi saddle or saddle.

3. A mechanism as described in claim 1, which is characterized by thatcompressible fill material(DM) is placed in the form of plate only either on the crown of the flexible pipe or under the invert of the flexible pipe,

4. A mechanism as described in any of the preceding claims, which is characterized by that compressible fill material(DM) is placed in contact with the flexible pipe(GEB).

5. A mechanism as described in claim 5 , which is characterized by that compressible fill material(DM) is placed as at least a single layer

6. A mechanism as described in claim 6, which is characterized by that compressible fill material(DM) as a single layer is placed

7. A mechanism as described in claim 7, which is characterized by that Expanded Polystyrene Geofoam (EPS ) is used as compressible fill material(DM)

8. After preparing the foundation(T) soil in accordance with the standards where the pipe(GEB) will be buried,

- The compressible fill material(DM) is placed so as to contact or not to contact with the flexible pipe(GEB) on the crown and/or under the invert of the pipe(GEB) in the form of plate or in the form of semi-saddle or in the form of saddle;, - The sides and on of the flexible pipe(GEB) are backfilled(DZ) with an appropriate soil material by, for example, AASHTO M145 and so the process of burying of the pipe is completed;

- Since the rigidity of the compressible fill material(DM) used for the process of each placement scheme on the flexible pipe(GEB) is very low compared to that of the sidefill(YD) soils, the soil prism on the pipe will settle more than the sidefill(YD) soil prisms;

- Furthermore, an arching mechanism will be developed irrespective of the vertical deflection of the flexible pipe(GEB) by this process which will cause the load to be transmitted from the soil mass that will settle to the side- fill(YD) that remains static.

As a result, the deformations are reduced as the stresses acting on the flexible pipe (GEB) will decrease.

9. Compressible fill material(DM) in the form of plate on the crown (TA) of flexible pipe,

- Preparation of the foundation(T) soil in accordance with the standards(lOla)

- Placement of the flexible pipe(GEB) on the foundation(T) soil(102a).

- Filling the sides(YAD) of the flexible pipe(GEB) up to the top of the pipe(GEB) with an appropriate backfill material (DZ) in a controlled manner(103a)

- Placement of compressible fill material(DM) in the form of plate on the pipe(GEB) (104a)

- Filling the top of the compressible fill material(DM) with an appropriate backfill material(DZ) in a controlled manner(105a)

A method, which is characterized by the process of placement according to the steps described in claim 9(100).

10. The compressible fill material(DM) under the invert(BT) of the flexible pipe from underneath of the pipe(GEB)

- Preparation of the foundation(T) soil in accordance with the standards(lOlb) - Placement of compressible fill material(DM) on the foundation(T) soil in the form of plate(102b)

- Placement of the flexible pipe(GEB) on the compressible fill material(DM) (103b)

- Filling first the sides(YAD) of the flexible pipe(GEB), then the top of the pipe(GEB) with an appropriate backfill material(DZ) in a controlled manner(104b)

A method, which is characterized by the process of placement according to the steps described in claim 9 (100)

11. The compressible fill material(DM) is placed in the form of plate on the crown(TA) and under the invert(BT) of the flexible pipe(GEB) from underneath;

- Preparation of the foundation(T) soil in accordance with the standards(lOlc)

- Placement of compressible fill material(DM) on the foundation(T) soil in the form of plate(102c)

- Placement of flexible pipe(GEB) on the compressible fill material(DM)(103c)

- Filling first the sides(YAD) of the flexible pipe(GEB), then the top of the pipe with the backfill(DZ) material in a controlled manner(104c)

- Placement of compressible fill material(DZ) in the form of plate on the crown (TA) of flexible pipe(GEB)(105c)

- Filling the sides and top of the compressible fill material(DM) with an appropriate backfill material (DZ) in a controlled manner(106c)

A method, which is characterized by the process of placement according to the steps described in claim 9 (100).

12. Compressible fill material(DM) under the invert(BT) of the flexible pipe(GEB) from underneath and on the crown(TA) of the pipe in the form of semi-saddle;

- Preparation of the foundation(T) soil in accordance with the standards(lOld) - Placement of compressible fill material(DM) on the foundation(T) soil in the form of semi- saddle (102d)

- Placement of the flexible pipe(GEB) on the compressible fill material(DM) in the form of semi-saddle (103d).

- Filling the sides(YAD) of flexible pipe(GEB) up to the horizontal symmetrical line(YSC) with an apropriate backfill material(DZ) in a controlled manner(104d). - Placement of compressible fill material(DM) in the form of semi-saddle on the crown(TA) of the flexible pipe(GEB)(105d)

- Filling the sides and top of the compressible fill material(DM) in the form of semi-saddle with an apropriate backfill material(DZ) in a controlled manner (106d).

13. Compressible fill material(DM) under the invert(BT) of the flexible pipe from underneath and on the crown(TA) of the pipe as a saddle;

- Preparation of the foundation(T) soil in accordance with the standards(lOle)

- Placement of compressible fill material(DM) on the foundation(T) soil in the form of saddle(102e)

- Placement of the flexible pipe(GEB) on compressible fill material(DM) in the form of saddle(103e)

- Placement of the compressible fill material(DM) in the form of saddle on top of flexible pipe(GEB)(104e)

- Filling the sides and top of the compressible fill material(DM) in the form of saddle with an apropriate backfill material (DZ) in a controlled manner (105e)

A method(lOO) as described in claim 9, characterized by placement according to the steps.

14. A method(lOO) as described in any one of claims from 9 to 14, characterized by the use of Expanded Polystyrene (EPS) Geofoam material as compressible fill material(DM).