COMPRESSIBLE GROUT MIX FOR USE IN ABSORBING COMPRESSIVE OR DEFORMATION STRESSES

Abstract

The present invention relates to a compressible grout mix for use as a fill in applications requiring absorption of compressive or deformation stresses between subterranean formations and subterranean structures as well as a method of filling a gap between subterranean formations and subterranean structures in a subterranean formation subject to compressive or deformation stresses utilizing the compressible grout mix for resilient absorption of forces in the hardened state of the compressible grout mix exerted by the time dependent deformation of the rock wall surface into the tunnel opening. The compressible grout mix contains hydraulic binding agent, polymer foam particles, anti-wash agent, and water and the method includes: a. providing the compressible grout mix containing hydraulic binding agent, polymer foam particles, anti-wash agent, and water, b. placing the compressible grout mix in the gap between the subterranean formation and the subterranean structure, and c. allowing the compressible grout mix to set, wherein the compressible grout mix in the hardened state has a compressible ratio greater than the anticipated compressive and deformation stresses of the subterranean formation.

Claims

1. A method of filling a gap between a subterranean formation and a subterranean structure where the subterranean formation is subject to the possibility of compressive and deformation stresses and possibly fluid seepage after excavation utilizing a compressible grout mix to be placed in the gap between the subterranean formation and the subterranean structure for resilient absorption of forces in a hardened state of the compressible grout mix exerted by the compressive and deformation stresses of the subterranean formation against the subterranean structure, the method comprising: a. providing the compressible grout mix comprising hydraulic binding agent, polymer foam particles, anti-wash agent, and water, b. placing the compressible grout mix in the gap between the subterranean formation and the subterranean structure, and c. allowing the compressible grout mix to set, wherein the compressible grout mix in the hardened state has a compressible ratio greater than anticipated compressive and deformation stresses of the subterranean formation.

2. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 1 wherein the hydraulic binding agent is a Portland cement.

3. The method of filling a gap between a subterranean formation and a subterranean structure in claim 2 wherein the anti-wash agent is one or both of alkyl aryl sulfonate and alkyl ammonium salt.

4. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 3 wherein the compressible grout mix also includes a water reducing admixture and/or a setting retarding admixture.

5. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 3 wherein the water reducing admixture is a polycarboxylate composition.

6. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 3 wherein the polymer foam particles are polymer foam beads.

7. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 6 wherein the polymer foam beads are an expanded polystyrene foam beads.

8. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 5 wherein the compressible grout mix comprises at least 10% volume Portland cement, between 40% volume and 60% volume of water, between 30% volume and 45% volume of polymer foam beads, between 0% volume and 15% volume of air, between 0.2% volume and 4% volume of the anti-wash agent, and between 0% volume and 1.0% volume of water-reducing admixture.

9. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 8 wherein the compressible grout mix comprises at least 10% volume Portland cement, between 45% volume and 55% volume water, between 35% volume and 40% volume of polymer foam beads, between 0% volume and 12% volume of air, between 0.3% volume and 3% volume of the anti-wash agent, and between 0% volume and 0.7% volume water-reducing admixture.

10. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 9 wherein the compressible grout mix comprises about 45% volume water, about 35% volume expanded polystyrene beads, about 10% volume Portland cement, about 1.8% volume anti-wash agent, about 8% volume air and about 0.2% volume water-reducing admixture.

11. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 1 wherein the subterranean formation is a tunnel rock formation subject to time dependent deformation and the possibility of fluid seepage after excavation and the subterranean structure is a tunnel liner.

12. The method of filling a gap between a subterranean formation and a subterranean structure as claimed in claim 1 wherein the subterranean formation is a subterranean formation subject to the possibility of seismic activity and the subterranean structure is a building foundation, a subterranean tunnel, utility service mains or piping.

13. A compressible grout mix for filling a gap between a subterranean formation and a subterranean structure where the subterranean formation is subject to the possibility of compressive and deformation stresses and possibly fluid seepage after excavation utilizing the compressible grout mix to be placed in the gap between the subterranean formation and the subterranean structure for resilient absorption of forces in a hardened state of the compressible grout mix exerted by the compressive and deformation stresses of the subterranean formation against the subterranean structure, the compressible grout mix comprising hydraulic binding agent, polymer foam particles, anti-wash agent, and water, wherein the compressible grout mix in the hardened state has a compressible ratio greater than anticipated compressive and deformation stresses.

14. The compressible grout mix as claimed in claim 13 wherein the hydraulic binding agent is a Portland cement.

15. The compressible grout mix as claimed in claim 13 wherein the anti-wash agent is one or both of alkyl aryl sulfonate and alkyl ammonium salt.

16. The compressible grout mix as claimed in claim 15 wherein the compressible grout mix also includes a water reducing admixture and/or a setting retarding admixture.

17. The compressible grout mix as claimed in claim 16 wherein the water reducing admixture is a polycarboxylate composition.

18. The compressible grout mix as claimed in claim 15 wherein the polymer foam particles are polymer foam beads.

19. The compressible grout mix as claimed in claim 18 wherein the polymer foam beads are an expanded polystyrene foam beads.

20. The compressible grout mix as claimed in claim 18 wherein the compressible grout mix comprises at least 10% volume Portland cement, between 40% volume and 60% volume of water, between 30% volume and 45% volume of polymer foam beads, between 0% volume and 15% volume of air, between 0.2% volume and 4% by volume of the anti-wash agent, and between 0% volume and 1.0% volume of the water-reducing admixture.

21. The compressible grout mix as claimed in claim 18 wherein the compressible grout mix comprises at least 10% volume Portland cement, between 45% volume and 55% volume water, between 35% volume and 40% volume of polymer foam beads, between 7% volume and 12% volume of air, between 0.3% volume and 3% volume of the anti-wash agent, and between 0% volume and 0.7% volume of the water reducing admixture.

22. The compressible grout mix as claimed in claim 18 wherein the compressible grout mix comprises about 45% volume water, about 35% volume expanded polystyrene beads, about 10% volume Portland cement, about 1.8% volume anti-wash agent, about 8% volume air and about 0.2% volume water reducing admixture.

23. The compressible grout mix as claimed in claim 13 wherein the subterranean formation is a tunnel rock formation subject to time dependent deformation and the possibility of fluid seepage after excavation and the subterranean structure is a tunnel liner.

24. The compressible grout mix claimed in claim 13 wherein the subterranean formation is a subterranean formation subject to the possibility of seismic activity and the subterranean structure is a building foundation, a subterranean tunnel, utility service mains or piping.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] A preferred embodiment of the use of the compressible grout mix and method of the present invention is illustrated in the attached drawing in which:

[0026] FIG. 1 is a cross section of a tunnel constructed in accordance with the present invention using pre-cast concrete segments, and

[0027] FIG. 2 illustrates the design requirement for a tunnel with time dependent deformation with stiffness between 0.5 MPa to 2.5 MPa.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention is directed to a compressible grout mix for filling a gap between a subterranean formation and a subterranean structure where the subterranean formation is subject to the possibility of compressive and deformation stresses and possibly fluid seepage after excavation utilizing a compressible grout mix to be placed in the gap between the subterranean formation and the subterranean structure for resilient absorption of forces in the hardened state of the compressible grout mix exerted by the compressive and deformation stresses of the subterranean formation against the subterranean structure, the compressible grout mix comprising hydraulic binding agent, polymer foam particles, anti-wash agent, and water, wherein the compressible grout mix in the hardened state has a compressible ratio greater than the anticipated compressive and deformation stresses.

[0029] The subterranean formation subject to the possibility of compressive and deformation stresses and possibly fluid seepage after excavation includes a seismic zone subject to earthquakes. In those situations, the compressive and deformation stresses from an earthquake are transferred through the subterranean formation and can cause cracking and damage to subterranean structures. Another example of a subterranean formation subject to the possibility of compressive and deformation stresses and possibly fluid seepage is time dependent rock formations (swelling rock), where the deformations can be significant and forces from the rock could damage the subterranean structure over a period of time.

[0030] The subterranean structure includes foundations of buildings, underground tunnels or utility service mains or piping.

[0031] The compressible grout mix contains hydraulic binding agent, polymer foam particles, anti-wash agent, and water. The compressible grout mix may also contain other optional ingredients so long as they do not impact the compressibility of the compressible grout mix as described in detail below.

[0032] The hydraulic binding agent should include at least one cement or may be a mixture of more than one type of cement and may optionally also include other hydraulic binding agents. Preferably, the hydraulic binding agent is a single cement, more preferably a Portland cement, and most preferably a GU Portland cement.

[0033] The polymer foam particles may be shredded polymer foam particles or may be formed particles such as beads. Preferably, the polymer foam particles are an expanded foam bead such as polystyrene, particularly expanded polystyrene. The polymer foam beads provide for compressible aggregates in the compressible grout mix in the hardened state as they are easily compressed under pressure. Preferably, the polymer foam beads have a particle size of between 8 and 30 mesh, most preferably about 16 mesh.

[0034] The anti-wash agent is present to avoid the segregation of grout in any fluid which may be present in the tunnel, reduce the floating of the polymer foam particles on the grout surface and help the polymer foam particles to stick to the hydraulic binding agent and avoid the floating of the polymer foam particles on the surface of the grout. Preferably, the anti-wash agent is one or both of alkyl aryl sulfonate and alkyl ammonium salt, more preferably a mixture of both of alkyl aryl sulfonate and alkyl ammonium salt, and most preferably a 1:1 mixture of alkyl aryl sulfonate and alkyl ammonium salt. Examples of the alkyl aryl sulfonate and alkyl ammonium salt are VISCO TOP available from Kao Corporation.

[0035] The water is used to activate the cement and thus lead to the hardening of the compressible grout mix. The water is also used to produce the compressible grout mix, to properly mix the components and to provide the desired flowability to the compressible grout mix for handling and pumping.

[0036] The compressible grout mix of the present invention preferably also contains other optional ingredients so long as they do not impact the compressibility of the compressible grout mix. Such optional ingredients include one or more of water reducing admixtures, setting retarding admixtures, and air and/or aggregates, preferably aggregates which increase the compressibility of the compressible grout mix.

[0037] The water-reducing admixture and/or the setting retarding admixture may be utilized to reduce the water content in the compressible grout mix and/or to slow the setting rate of the cement while retaining the flowing properties of the compressible grout mix to make them more suitable to work. The water-reducing admixture is at least one water-reducing admixture or may be a mixture of more than one type of water-reducing admixture. Preferably, the water-reducing admixture is one or both of a high rate water reducer such as a sulphonate or polycarboxylate, or a water-reducing and setting retarding admixture such as an acidic water-reducing and setting retarding admixture preferably, those containing phosphonic acid, more preferably one or both of the high rate water reducer such as MASTERGLENIUM 7700 and the water-reducing and setting retarding admixture such as MASTERSET DELVO both available from BASF Corporation.

[0038] Air may be added to the compressible grout mix to aid in the flowability of the mix as well as to provide for voids to aid in the compressibility of the hardened compressible grout mix.

[0039] The compressible grout may also include other aggregates such as sand, clay or other particulate material. Preferably, the aggregate increases the compressibility of the compressible grout mix.

[0040] One example of an aggregate which increases the compressibility of the compressible grout mix is a bentonite clay. The bentonite clay in the compressible grout mix is utilized to create micro voids in the hardened compressible grout mix owing to the ability of the bentonite clay to swell when in a wet state and shrink as the compressible grout mix is cured. Preferably the bentonite clay is a sodium bentonite clay utilized in a powder form with a particle size of 200 mess or less.

[0041] The compressible grout mix is prepared in the usual manner by first combining the hydraulic binding agent, anti-wash agent, and water along with any optional ingredients such as one or more of water reducing admixtures, setting retarding admixtures, and air and/or aggregate, preferably aggregates that increase the compressibility of the compressible grout mix to produce a paste. The polymer foam beads are then added and mixed to form the final compressible grout mix which can then be dispensed in the usual manner as described below.

[0042] The proportions of the ingredients are selected based upon the desired compressibility of the compressible grout mix in the hardened state which is in turn based on the expected compressive and deformation stresses of the subterranean formation. The compressible grout mix is formulated to provide a compressible ratio in the hardened state greater than the anticipated compressive and deformation stresses of the subterranean formation. Preferably, the formulation provides a compressible ratio up to twice the anticipated compressive and deformation stresses of the subterranean formation. For example, Georgian Bay Shale has been found to have time dependent horizontal and vertical free swell rates of from 0.05 percent to 0.5 percent and from 0.1 percent to 2.5 percent per log cycle of time respectively. For in situ stresses, the baseline maximum major and minor horizontal stresses are between 6 MPa and 12 MPa and between 2 MPa and 9 MPa, respectively. In these situations, a compressible grout mix capable of supporting up to 20 percent compression as measured by ASTM standard testing protocol ASTM D7012-14 in the hardened state would be able to absorb the time dependent deformation in such rock structure. FIG. 2 illustrates the design characteristics of a compressible grout for such an application.

[0043] The proportions of the ingredients are preferably based upon the percent of the total volume of the final compressible grout mix. Thus, the higher the proportion of the polymer foam, as well as the other additives which increase the compressibility of the compressible grout mix in the compressible grout mix, the more compressible the compressible grout mix will be. However, in order to allow the compressible grout mix to cure and harden, there should be a minimum amount of the hydraulic binding agent in the compressible grout mix. Generally, the compressible grout mix will have the hydraulic binding agent present in a minimum amount of about 10 percent by volume of the total compressible grout mix.

[0044] For most compressible grout mixes according to the present invention, the largest proportion ingredient of the compressible grout mix will be water which will generally be present in an amount in proportion to the amount of hydraulic binding agent in the compressible grout mix. For most applications, the water will be present in an amount between about 40 percent and 60 percent of the total volume of the compressible grout mix, preferably in an amount between 45 percent and 55 percent of the total volume of the compressible grout mix.

[0045] The proportion of the polymer foam beads is generally the second highest proportion ingredient in the compressible grout mix and has the greatest impact on the compressibility of the hardened compressible grout mix. The proportion of the polymer beads in the compressible grout mix can vary between about 30 percent and 45 percent of the total volume of the compressible grout mix, preferably between about 35 percent and 40 percent of the total volume of the compressible grout mix.

[0046] The proportion of the anti-wash agent in the mixture will generally vary between 0.2 and 4.0 percent of the total volume of the compressible grout mix, preferably between about 0.3 and 3.0 percent of the total volume of the compressible grout mix.

[0047] The proportion of any of the one or more water-reducing admixture and/or the setting retarding admixture utilized to reduce the water content in the compressible grout mix and provide flowability and setting benefits will generally vary between about 0.1 percent and 1.0 percent of the total volume of the compressible grout mix, preferably between about 0.2 percent and 0.7 percent of the total volume of the compressible grout mix.

[0048] The proportion of any air in the compressible grout mix will impact the compressibility of the hardened compressible grout mix although to a lesser degree than the polymer foam beads. The proportion of any air in the compressible grout mix can vary between about 5 percent and 15 percent of the total volume of the compressible grout mix, preferably between about 7 percent and 12 percent, most preferably between about 7 percent and 10 percent of the total volume of the compressible grout mix.

[0049] The proportion of the other aggregate, preferably an aggregate which increases the compressibility of the compressible grout mix such as a bentonite clay will generally vary between about 0 percent and 5.0 percent of the total volume of the compressible grout mix, preferably between about 0 percent and 2.0 percent of the total volume of the compressible grout mix.

[0050] In a preferred embodiment, the present invention relates to a compressible grout mix for use as an annular fill between a tunnel liner and a tunnel wall of a tunnel bored in a time dependent deformation rock formation particularly where the possibility of fluid seepage is present. In addition, the present invention provides a method of filling an annular gap between a tunnel rock wall surface and a tunnel liner of a tunnel in a rock formation subject to time dependent deformation and the possibility of fluid seepage after excavation. The compressible grout mix is placed in the annular gap between the tunnel rock wall surface and the tunnel liner for resilient absorption of forces in the hardened state of the compressible grout mix exerted by the time dependent deformation of the rock wall surface into the tunnel opening.

[0051] The utilization of the compressible grout mix of the present invention as an annular fill between a tunnel liner and a tunnel wall of a tunnel bored in a time dependent deformation rock formation is illustrated in FIG. 1. The tunnel 10 is bored through the subterranean rock 12 utilizing a tunnel boring machine (TBM) (not shown). The bored tunnel diameter is larger than the diameter of the liner 14 which can be steel reinforced concrete, fiber reinforced concrete, steel or other material in pre-cast segments. Preferably, the segmented liner 14 is steel reinforced concrete or fiber reinforced concrete. As the tunnel 10 is being bored, the segmented liner 14 is installed to the rear of the TBM and an annular gap 16 is provided between the segmented liner 14 and the tunnel wall surface 18. Generally, the annular gap 16 will have a depth of 50 mm or more between the segmented liner 14 and tunnel wall surface 18. The annular gap 16 is filled with the compressible grout mix 20 of the present invention in typical fashion either by manually pumping through grout holes 22 provided in the liner as illustrated in FIG. 1 or in an automated pumping operation at the rear of the TBM. Once the compressible grout mix cures and hardens, it is capable of resiliently absorbing the forces exerted by the time dependent deformation of the tunnel wall surface into the tunnel opening.

[0052] The preparation and properties of a preferred embodiment of a compressible grout mix of the present invention will now be described in the following examples which are for purposes of illustration only and are not to be construed as limiting the invention as described above.

EXAMPLE 1

Preparation of Compressible Grout Mix

[0053] 390 kg of GU Portland cement were mixed with 400 liters of water to achieve a paste. To the paste, 2.5 liters of MASTERSET DELVO, 15 liters of a 1:1 mixture of VISCO TOP 100A and VISCO TOP 100B, 16 kg of ELEMIX EPS beads with an average particle size of 16 mesh were added along with 88 liters of water and mixed thoroughly. This resulted in 1.0 m.sup.3 of compressible grout mix having a weight of 911 kg. The compressible grout mix contained 48.8 volume percent water, 38.1 volume percent ELEMIX beads, 12.4 volume percent GU Portland cement, 1.5 volume percent VISCO TOP, and 0.3 volume percent MASTERSET DELVO.

EXAMPLE 2

Preparation of a Further Embodiment or the Compressible Grout Mix

[0054] 360 kg of GU Portland cement were mixed with 400 liters of water to achieve a paste. To the paste, 22 kg of a 1:1 mixture of VISCO TOP 100A and VISCO TOP 100B, 8 kg of ELEMIX EPS beads with an average particle size of 16 mesh were added along with 293 liters of water and mixed thoroughly

[0055] Concrete core specimens were prepared utilizing the compressible grout mix prepared in accordance with Example 2 above. Each of the samples had a length of approximately 20 cm and a diameter of approximately 10 cm. Two samples were tested using standard ASTM testing protocol (ASTM D7012-14) for unconfined compression strength analysis. For all of the above testing, each sample was cut to prepare cylindrical samples having nearly parallel end faces. The testing was conducted to failure within a servo controlled compression frame. All tests were performed under axial strain control at rates approximating 210.sup.4 s.sup.1 (equivalent to an axial deformation rate of 0.033 mm/s) and for these tests, simultaneous recording of axial force and axial deformation was performed from which determination of standard failure parameters (Young's modulus and peak compressive strength) were made and each unconfined compression test was permitted to undergo axial deformation equivalent to 20% axial strain prior to completion of testing. The results of all of the above testing are illustrated in the following Table 1.

TABLE-US-00001 TABLE 1 Sample Compression Strength Failure Test Results Sample & Cure Age (with anti wash agent) MPa Sample 1 (7 days) 2.0 Sample 2 (7 days) 1.96 Sample 1 (28 day) 2.51 Sample 2 (28 day) 2.56

[0056] The compressible grout mix of the present invention provides a stable backfill for the concrete segments accommodating the deformation of the annular space, particularly where the possibility of fluid seepage is present. The compressible grout mix helps to minimize settlement of the tunnel liner while holding the segments of the tunnel liner in place during the tunnel boring operation. The compressible grout mix ensures that there is uniform contact between the tunnel liner and the tunnel wall surface. The compressible grout mix also reduces the surface settlement over the tunnel. If the void is not filled with compressible grout mix, the ground will move into the void resulting in settlement. The compressible grout mix also acts as a backup to the gasket minimizing water leakage and penetration of gases into the tunnel thus aiding in reducing seepage and loss of fine particles and water where the gaskets provided between the tunnel segments become ineffective or damaged.

[0057] The compressible grout mix of the present invention is engineered for the specific application based upon the characteristics of the rock formation through which the tunnel is being bored. In the specific example provided above, the compressible grout mix has been formulated to accommodate the expected time dependent deformation found in Georgian Bay shale common in southern Ontario. However, utilizing the teaching of the present application, the formulation of the compressible grout mix of the present invention may be easily modified to accommodate rock formations having different time dependent deformation and fluid seepage characteristics simply by adjusting the proportions of the compressible materials in the compressible grout mix, namely the expanded foam beads, and air, as well as the anti-wash agent.

[0058] The specific examples set out above relate to the use of the compressible grout mix for use in filling an annular gap between a tunnel rock wall surface and a segmented concrete tunnel liner. The compressible grout mix is also useful in other applications where an annular gap between a tunnel wall and tunnel liner has to be filled. For example, in situations where a temporary steel liner is installed prior to a final liner of cast in place concrete, the compressible grout may be used in the annular gap between the tunnel wall and tunnel liner. The compressible grout of the present invention is also useful for filling gaps between other precast structures and time dependent deformation rock formations where the possibility of fluid seepage exists. Other uses of the compressible grout of the present invention will be apparent to those of skill in the art.

[0059] While preferred embodiments of the present invention have been illustrated in the present application, it will be appreciated by those of skill in the art that variations may be made thereto without departing from the scope of the invention as expressed in the appended claims.