2559 m-bey-100 tu0-ctbt-mst-000015-001_annulus grouting

Riyadh Metro Project

Document No: M-BEY-100TU0-CTBT-MST-000015

Revision: 001

Approval Code:

Code 1 Work May Proceed.

Code 2 Revise and Resubmit. Work May Proceed Subject to Resolution of Indicated.

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Permission to proceed does not constitute acceptance or approval of Design Details, Calculations, Analyses, Test Methods, or Materials Developed or Selected by the Subcontractor/Supplier, and does not relieve Subcontractor/Supplier from full compliance with contractual obligations or release any “Holds” Placed on the Contract.

Responsible Engineer (RE): Date Issued:

ANNULUS GROUTING

DOĞUŞ İnşaat ve Ticaret A.Ş. METHOD STATEMENT FOR ANNULUS GROUTING

Doc. Code : M-BEY-100TU0-CTBT-MST-000015 Revision : 001 Date : 03.06.2015 Page : 1/14 _____________________________________________________________________________________________________________

The version of this document that is available in the section defined for the system documents in the electronic environment is up-to-date and valid. In case the red seal of “CONTROLLED COPY” is lacking on the printed copies, it should be understood that sufficient assurance in

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RIYADH METRO PROJECT PACKAGE 1

LINE 1 TUNNELING SERVICES

METHOD STATEMENT FOR ANNULUS GROUTING

Document No: M-BEY-100TU0-CTBT-MST-000015

Rev Rev

Status Date

Prepared by Reviewed by Approved by

001 For

Review 03.06.2015 P.Brankov S.Ergut E. Yapici

Engineer Review Status Date: Name:

A – REVIEWED; WORK MAY PROCEED

B – REVIEWED WITH COMMENTS; REVISE AND RESUBMIT; WORK MAY PROCEED SUBJECT TO INCORPORATION OF COMMENTS

C – OBJECTION, REVISE AND RESUBMIT; WORK MAY NOT PROCEED

D – REJECTED

E – REVIEW NOT REQUIRED; WORK MAY PROCEED

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CONTENTS

1. PURPOSE .......................................................................................................................... 3

2. SCOPE ............................................................................................................................... 3

3. REFERENCES ................................................................................................................... 5

4. DEFINITIONS ..................................................................................................................... 5

5. ROLES & RESPONSIBILITES ........................................................................................... 5

6. PROCEDURE ..................................................................................................................... 6

7. GROUTING METHODS ...................................................................................................... 8

8. MATERIAL ......................................................................................................................... 9

8.1 CHARACTERISTICS OF TWO COMPONENT GROUT MATERIAL ............................................................... 10 8.2 DISTRIBUTION OF SEGMENTAL LINING PRESSURE .............................................................................. 11

9. PERFORMANCE OF THE TWO COMPONENT ANNULUS GROUT .................................................... 11

9.1 CREATION OF THE ANNULAR UNCOMPRESSIBLE BUBBLE .................................................................... 11 9.2 DURABILITY OF THE ANNULAR TWO COMPONENT GROUT .................................................................... 13 9.3 CONSISTENCY AND COMPRESSION STRENGTH OF THE HARDENED MIX ................................................ 13

10. HEALTH&SAFETY AND ENVIRONMENT (HSE) ............................................................ 14

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1. PURPOSE

The intention of this method statement is to define and describe the process, operations and sequence of the construction methods that will be implemented to carry out the Annulus Grouting activities and to ensure the control of the potential ground movement and the surface settlements, to stabilize the segment lining in the ground and to improve the water tightness of the segmental lining during the tunnelling works for the Riyadh Metro Project-Package 1-Line 1 by the use of four EPB-Tunnel Boring Machines (TBM).

2. SCOPE

During the EPB-TBM tunnel excavation, the machine excavates slightly more soil than is taken up by the final lining. This is often referred to as “ground loss,” the term for the small excess of excavated volume. When tunneling with shield machines, prefabricated segments are installed for a tunnel lining. A circular annular gap (19cm) remains behind the shield tail, which is limited on the inside by the lining segments and on the outside by the surrounding ground. Such ground loss can produce surface settlement. The settlement can occur during the boring or, depending on ground conditions, days or weeks after the boring. The use of EPB TBMs minimizes this settlement. The width of the annular gap is caused by overcut, conicity of the shield skin and design of the seal.

Factors of influence on the width of the annular gap,the amount of ground surface settlement will be a function of tunnel depth, tunnel size, proximity of adjacent tunnels, ground conditions, TBM characteristics and excavation techniques. In addition to ensuring adequate face

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pressures through the use of pressurized-face TBMs, the requirement for precast segmental linings, grouted as the TBM advances, also minimizes settlement potential. In order to minimize settlements at the ground surface and to ensure good embedment of the segmental lining, the annular gap has to be filled with grout continuously during tunneling. The grouting operation is performed within the tunnel behind the TBM to promptly fill the annular space between the segmental lining and the surrounding ground. During tunnel advance the grouting of the annular gap and the embedment of the segmental lining are necessary to transmit the forces from the tunnel into the surrounding ground. The grouting material should at least have the same properties (or better) as the surrounding ground in the final state. Pressure is maintained at the face of the TBM tunnel excavation to reduce the potential for ground loss, soil instability, and surface settlement. In addition, a rigid, precast, bolted, sealed lining system would be employed. In combination with the face pressure, grout would be injected immediately behind the TBM, in the annular space between the installed precast concrete liners (tunnel rings) and the excavated ground.

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Ground settlements during TBM advancing

3. REFERENCES

Specifications - Construction of TBM Tunnels-Riyadh Metro Line 1 (Document No.M-BD2-000000-CTB-ESP-000002)

4. DEFINITIONS

MS : Method Statement WP : Work Package ITP : Inspection Test Plan JHA : Job Hazardous Analysis

5. ROLES & RESPONSIBILITES

Prepared by : TBM Department Controlled by : QC Manager Approved by : Project Manager To be Apply : TBM Manager

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6. PROCEDURE

The instantaneous filling of the annulus that is created behind the segment lining at the end of the tail during the TBM advance is an operation of paramount importance. Its main goal is to minimize the surface settlements due to any over-excavation generated by the passage of the TBM. To correctly achieve the goals, a simultaneous backfilling system and the injected material should satisfy the technical, operational and performance characteristics. A two-component system injection for the back-filling is progressively substituting the use of traditional mortars. The main reasons that the TBM applies a two component annulus grouting method between the TBM excavation and segmental lining, throughout the tail skin grout injection system and during the TBM advance, are:

a) to prevent the ground movement and the surface settlements due to the volume loss at the tail void,

b) to stabilize the segment lining in the ground and c) to improve water tightness of the segmental lining.

Full-face shield machines have shown an ever increasing number of applications thanks to their ability to minimize and control surface subsidence when a tunnel is excavated with a low overburden. The excavation using these machines is made by a rotating cutter-head fitted with pick or disk cutters or a combination of both, while the face stability is guaranteed by the pressure in the bulk chamber, behind the cutter head, obtained with conditioned soil Earth Pressure Balance Shields (EPB Machine). The tunnel is then supported by a segmental lining that is installed continuously during the advance of the machine and this works as the final lining too. To permit the advance of the machine and of the shield, and for technological reasons, the excavation diameter is usually bigger than the external diameter of the final lining due to the overcutting necessary to permit the advancing of the shield, to the conicity of the shield itself and to the thickness of the shield. For these reasons, around the lining there is an open space that must be continuously filled during the machine’s advance. The instantaneous filling of this “annulus”, which is created behind the segment lining at the end of the shield tail, is an operation of paramount importance for the correct mechanized tunneling procedure, particularly in an urban area. Its main goal is to minimize surface settlements due to any over-excavation generated by the passage of the TBM. Furthermore, the back-filling operation has to: – lock the segmental lining into position, avoiding movement owing to both segmental self-weight and the thrust forces, hoop stresses, generated by the TBM; – bear the loads transmitted by the TBM back-up weight; – ensure a uniform, homogeneous and immediate contact between the ground and the lining; – avoid puncture loads by ensuring the application of symmetrical and homogeneous loading along the lining; – complement the waterproofing of the tunnel with the concrete lining and sealing (i.e., if the lining has cracks due to a wrong installation, back-fill grout should help to mitigate any water inflow).

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Regarding the stability of the segmental lining in the ground the back fill injection: a) Pressure is almost uniform acted on the segmental lining when the lining to be came out

from the TBM tail body. b) It generates axial force into the lining and minimizes the tensile strength due to the

bending movement. c) The back fill grout material is to be hardened, so it will be able to transmit the tunnel

deformation to the ground. d) It is also taking subgrade reaction force of the side ground to prevent the excessive

deformation of the tunnel. Figure 3 is a diagram on the stability of segment lining in the ground.

Figure 3 – Stability of the Segmental lining in the ground

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7. GROUTING METHODS

Two different methods to fill the annular gap with grouting material have been established. On the one hand it is possible to transport the grouting material through segmental lining into the annular gap; on the other hand grout supply lines can be used to fill the annular ring. The latter method is also called grouting through the tailskin. Grouting through the tailskin – Primary Grouting In soft ground it is necessary to fill the annular gap continuously with mortar. Therefore grouting technology through the tailskin was developed. Using this method, the mortar is pumped through a grout supply line into the gap. Generally, the width of the grout supply line changes from a diameter of 65 mm to an oval cross-section which has with the same cross-sectional area.

A component is composed of mainly cement and bentonite, and B component is accelerator based on sodium silicate. The components A and B are being pressurized through the injection pumps. These two liquids are mixed and gel at the injection point in the tail void and filled into the tail void by pressurizing of the injection pump. The separation of the water and the aggregate (bleeding) is very little and the injection part is few. Also the load of the injection pumps is low. The material gels after the mixing of component A with component B. After gel no remarkable strength is generated in this material for 10-20min. This material obtains strength of around 100kN/mm2 after 1 hour later and hardens rapidly afterwards.

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There is no influence with the ground water as the material is not diluted and flowed out, because of gel. This material can pumping force feed the distance of about 2km, because of the good liquidity. This method can be demonstrated good back filling in various ground conditions. Moreover, because the material generates strength at the early stage, the ground and the tunnel can be supported sufficiently. Therefore, the ground settlement and the deformation of the tunnel are very small under the condition of swallow ground cover and soft ground.

8. MATERIAL

Grout with two components has been developed to achieve good pumpabilty / workability and a quick setting. Both components have slurry consistency in order to pump them close to the annular gap where they are mixed. One component is cement bentonite slurry. The other component is a hardener or activator. After a short reaction time a gel is generated. The reaction time of the grout can be influenced by controlling the volume flow of those both components.

(with BASF Chemicals)

(with FOSROC Chemicals)

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Using BASF+FOSROC Chemicals

8.1 CHARACTERISTICS OF TWO COMPONENT GROUT MATERIAL

Component A mainly consists of cement and bentonite and Component B consists of sodium silicate. It takes 5-10sec, after mixing A and B liquids, the material become to gel. During 10-25min and with an approximate strength of 0-1kN/mm2 the material sustains a plastic state and fluidizes easily when pressure is applied. After passing 30min the material is getting hardened quickly up to strength of about 100kN/mm2 after an hour and continues hardens rapidly afterwards.

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8.2 DISTRIBUTION OF SEGMENTAL LINING PRESSURE

At the tail skin passing time, almost same pressure distribution due to the injection is being observed. After 5 rings pass the pressure distribution is getting reduced and up to 1-6 months later the pressure distribution becomes ground pressure. Because the backfill material is low strength about one hour after the mixed A and B components, the bond strength of the backfill grout material is smaller enough than the strength of the tail brushes of TBM. Therefore, the tail brush is not damaged the adhesion of backfill material. The risk that the two components type backfill grout material is passing into the tail brush inside the TBM shield is lower, because of the low infiltration of this type of backfill material. When TBM is stopped for a long term the bentonite solution is filled to the injection tube. At this time the bentonite which leak out to the ground forms the protection cover between the tail brush and the backfill grout material. Therefore, the backfill material does not adhere to the tail brush.

9. PERFORMANCE OF THE TWO COMPONENT ANNULUS GROUT

9.1 CREATION OF THE ANNULAR UNCOMPRESSIBLE BUBBLE

As the injected material for the two-component system is an ultra-fluid liquid which, thanks to the addition of an accelerator admixture just before its injection, obtains a thixotropic consistency in a few seconds and as it is made up of a huge amount of water (approximately 800 liters per cubic meter of material), it is without doubt an uncompressible fluid, just like water. The consequence is that the annulus void that is created, after the TBM tail-skin passage, has to be considered as a closed annular bubble that is filled, instant per instant, with an uncompressible fluid.

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Therefore, every movement of the surrounding ground that tends to enter in the bubble or any movement of the concrete lining which tends to reduce the bubble volume instantaneously leads to the creation of another reaction-pressure in the ball, uniform along all the volume and above all the surfaces of the volume, which avoids any type of deformation. Therefore, the uncompressible ball of gel confines perfectly and completely everywhere the concrete rings already installed and the new concrete ring that has to be installed. In order that this can be effectively real, it is necessary that the following conditions are met: – The injected material must remain uncompressible; – The fluid cannot escape from the bubble; – It cannot permeate through the surrounding ground (this is avoided by the underground water that exerts a hydrostatic pressure on the injected material). – it cannot escape through the space between the tail and the excavation profile, that is avoided by a correct balance between the tunnel face pressure and the injection pressure (which must be approx. 0.2 bar higher, not more); – If the surrounding ground in bad condition tends to close towards the bubble, it cannot be allowed to move with excessive pressures; otherwise the pressure needed to advance the machine would increase too much. This has to be balanced and controlled with the right equilibrium between the pressure in the excavation chamber and the injection pressure. This can be aided by lubrication of the extrados of the tailskin with bentonite slurry. It is suggested that the bentonite slurry injection takes place exactly where the tail is blocked and weighs on the ground, which means behind the invert of the lining and in the final part of the tail; – The segment ring just installed cannot have deformations (in general, without ovalization) due to its own weight, which could lead to an anomalous installation of the rings or a too low pressure on the upper segments; – The gel cannot be leeched by the underground water. It is evident from the above reasons that it is necessary to inject a fluid that does not harden instantaneously, but that becomes a gel quickly and progressively without avoiding the formation of an uncompressible ball at constant volume. The long-term mechanical strength of the back-fill material does not have any meaning, because it does not give any structural contribution to bearing the hydrostatic and geostatic loads (these are completely supported by the concrete lining), but the gel has to be as homogeneous as possible in order to mitigate the external loads (a closed ball). To achieve this goal it is doubtless necessary that the gel cannot decompose after its injection: its durability must guarantee that the uncompressible annular ball is kept permanently. Therefore, all the attention should be paid to the behavior of the injected material at early stages (from the first seconds to some hours), which includes the injection and installation of some

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segment rings. It is evident that the existence of a closed uncompressible ball is the most efficient and important factor.

9.2 DURABILITY OF THE ANNULAR TWO COMPONENT GROUT

The durability of the gel that totally fills the annular bubble is guaranteed in the normal humidity conditions of the ground (even more when the tunnel is drilled under the water table). During the construction of many tunnels the authors understand that since the two-component system has started to be used, more than ten years ago, there has only been a positive indication of the grout’s durability. A comprehensive proof of the behavior for the future does not exist, but the gel must have two features that indicate its durability: – The undeform ability: this parameter immediately appears as the most significant, as the gel is made up principally of water. If the water is not lost (due to evaporation or filtration), the material will remain stable. It is, therefore, essential that the hosting ground keeps its natural humidity; – The technical impermeability of the ground (10-8 m/sec). This is the physical parameter that favors’ the creation of the situation described above. Both the mentioned characteristics can be measured in the laboratory and can be assumed as indicators of durability.

9.3 CONSISTENCY AND COMPRESSION STRENGTH OF THE HARDENED MIX

The first important consideration deriving from what has been written above is that, when a super-fluid two component mix is used, the early-stages mechanical strengths are more important than the latter stages: in fact, the concrete lining, not the back-filling, must bear all the hydrostatic and geostatic pressures. In the example of the Sofia Metro Line, it is clear from the table that the requested data are 0.03 MPa at 1 hour and 1.5 MPa at 24 hours and nothing is said about longer stages. This position appears to be absolutely correct because it is in the first hours (8 rather than 24 when the TBM advances regularly) that the gel must fill every void in the “annulus” (and eventually in the surrounding ground) and protect the segment lining. This is carried out thanks to the high fluidity of the injected material and its quick gel creation. Furthermore, the gel must block the ring in its projected position (avoiding the formation of point loads) and at the same time avoid the last installed rings deforming due to the TBM thrust and cutting-wheel rotation. It is of paramount importance that the mix creates a gel after a few seconds and so an incompressible closed ball is generated: therefore, the gel creation must be tested (at 0.5 and 8 hours stages the measures of mechanical strengths are suitable, for example, with a pocket penetrometer).

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The rationale of the half hour can be adjusted to suit the time taken to build one ring should be long enough for the grout to achieve sufficient strength to avoid floating around in the grout. Measures above the 24 hours are only suitable for checking that the gel does not decompose, but increases its strength in order to allow the extraction of cores through the segments, useful to directly check the effective total filling of the “annulus”. It is without doubt that a measure of the compressive strengths on cores extracted in situ (even if the coring partially disturbs the samples) is the most reliable and significant, because the material is injected into the “annulus” at pressure and there remains in environmentally natural conditions.

10. HEALTH&SAFETY AND ENVIRONMENT (HSE)

All Staff will use helmets, glass, gloves and safety shoes in accordance with HSE procedures.

2559 m-bey-100 tu0-ctbt-mst-000015-001_annulus grouting

Engineering

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