ADMIXTURE FOR PREVENTING SWELLING OF ANHYDRITE CONTAINING ROCK MATERIAL

Abstract

A chemical inhibitor is used for reducing and/or preventing swelling of anhydrite containing rock material, wherein, the chemical inhibitor is used during construction work, especially in tunnel construction through rock material, especially in drill and blast tunnel construction work and/or in tunnel construction with a tunnel boring machine.

Claims

1. A method for reducing and/or preventing swelling of anhydrite containing rock material, the method comprising: exposing the anhydrite containing rock material to an effective amount of chemical inhibitor to reduce and/or prevent swelling of the anhydrite containing rock material.

2. The method as claimed in claim 1, wherein the chemical inhibitor is at least one member selected from the group consisting of a dissolution inhibitor for anhydrite, a gypsum nucleation inhibitor and a gypsum crystal growth inhibitor.

3. The method as claimed in claim 1, wherein the chemical inhibitor comprises at least one carboxylic acid group, at least one amine group and/or at least one amide group.

4. The method as claimed in claim 1, wherein the chemical inhibitor comprises a reaction or condensation product of an amino acid and/or an amino acid derivate with an amine-free carboxylic acid and/or an amine free carboxylic acid derivative.

5. The method as claimed in claim 1, wherein the chemical inhibitor is at least one member selected from the group consisting of a polycarboxylic acid, a polyacrylic acid and a polymethacrylic acid.

6. The method as claimed in claim 1, wherein the chemical inhibitor is at least one member selected from the group consisting of a chelating compound, an aminopolycarboxylic acid, diethylene triamine pentaacetic acid, nitrilotriacetic acid, iminodiacetic acid, egtazic acid, 1,2-bis(o-aminophenoxy)ethane-N,N,N,N-tetraacetic acid, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, ethylenediamine-N,N-bis(2-hydroxyphenylacetic acid) and ethylene diamine tetraacetic acid.

7. The method as claimed in claim 1, wherein the chemical inhibitor does not comprise any positively charged groups and/or any quaternary amine groups.

8. The method as claimed in claim 1, wherein the chemical inhibitor is dissolved and/or dispersed in a fluid selected from the group consisting of a processing fluid, a processing liquid for construction work, a fluid comprising water, and a fluid consisting of water.

9. The method as claimed in claim 8, wherein a proportion of the chemical inhibitor is 0.001-50 wt. % with respect to the total amount of the fluid and the chemical inhibitor.

10. The method as claimed in claim 1, wherein the rock material comprises 0.01-100 wt. % of anhydrite with respect to the overall weight of the rock material.

11. The method as claimed in claim 1, wherein the rock material comprises 0.1-90 wt. % of clay.

12. The method as claimed in claim 1, wherein the anhydrite containing rock material is exposed to the chemical inhibitor during tunnel construction through rock material.

13. A composition comprising: a chemical inhibitor and anhydrite containing rock material, wherein the chemical inhibitor is present in an effective amount to reduce and/or prevent swelling of the anhydrite containing rock material.

14. A method comprising: performing construction work in rock material, the rock material including anhydrite containing rock material, where the construction work comprises performing tunneling and/or mining operations in the rock material, and adding to a processing fluid that contacts the rock material an effective amount of a chemical inhibitor to reduce and/or prevent swelling of the anhydrite containing rock material.

15. The method according to claim 14, wherein the chemical inhibitor is added to the processing fluid before the fluid contacts the rock material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The drawings used to explain the embodiments show:

[0073] FIG. 1 The experimental setup for oedometer experiments. An oedometer consists of a steel ring with a pressed sample inside, capped by two porous plates. One plate can move uniaxially to allow deformation (swelling) of the sample as it is wetted from the bottom used for testing swelling in anhydrite containing rock material;

[0074] FIG. 2 The results of oedometer test series. Two oedometers were saturated and placed in a 60 C. oven to allow clay swelling. At indicated point (T1), 1.sup.st oedometer was removed to 20 C. environment, where immediately ATG conversion took place as seen. At second indicated point (T2), 2.sup.nd oedometer was removed and placed in 20 C. environment, but fluid was replaced with 1% chemical inhibitor solution. ATG clearly is stopped as can be seen compared to 1.sup.st oedometer.

[0075] In the figures, the same components are given the same reference symbols.

EXEMPLARY EMBODIMENTS

[0076] 1. Methods

[0077] In order to test the ability of various substances to reduce swelling of anhydrite containing rock material, oedometer tests have been performed. Oedometers are well known devices in geological engineering.

[0078] FIG. 1 shows the oedometers 10, 20, 30 used for this invention. They consist of a steel ring 3 (cf. first oedometer 10) with a pressed sample (anhydrite containing rock material) inside, capped by two porous plates (not shown in FIG. 1). The upper plate can move uniaxially to allow deformation (swelling or consolidation) of the sample as it is wetted from the bottom through the other porous plate. For wetting, fluid lines 1 are connected to the lower portions of the oedometers which allow for introducing fluid into the steel ring 3. Put differently, the fluid, e.g. water, induces swelling (or consolidation) so that the upper porous plate is allowed to rise (or fall) in response to the wetted material, and the swelling is measured here with a gauge 4. Additionally, a counterpressure of about 5 kPa was imposed by placing a counterweight 2 on top of the upper plate. The rise of the upper plate upon swelling is a measure of the swelling strain or volume increase of the sample.

[0079] In order to exclude any interference with clay swelling, clay swelling and the anhydrite to gypsum (ATG) swelling were decoupled by running initial swelling experiments with pure water as wetting fluid in an oven at 60 C. It is known that at temperatures above approximately 42 C., the solubility of anhydrite is lower than that of gypsum, and therefore anhydrite is the most stable phase. Thus, at 60 C., anhydrite to gypsum (ATG) swelling is essentially excluded and any swelling occurring at this temperature is related to pure clay swelling.

[0080] Subsequently, the oedometers were taken out of the oven and placed in room temperature conditions. After some days (cf. results), the wetting fluids were replaced with fluids comprising chemical inhibitors as explained below. Apart from the differences explained below, all of the experiments have been performed under identical conditions.

[0081] Swelling of the samples (swelling strain) was recorded on a regular base, from the beginning of the experiments up to 70 days.

[0082] 2. Experiments and Results

[0083] 2.1 Experiment 1

[0084] In a first experiment, crushed rock powder from construction work at Belchen tunnel in Switzerland running through Swiss Gipskeuper formation (containing clay as well as anhydrite rock material) was pressed and placed in two oedometers 10, 20 and treated as described above with pure water as wetting fluid.

TABLE-US-00001 TABLE 1 Composition of rock material used in the experiments (Rietveld analysis) Component Proportion [wt. %] Anhydrite 43.1 Chlorite 4.5 Illite/Muscovite 6.5 Magnesite 11.6 K-feldspar 4.5 Pyritre 0.7 Quartz 5.1 Smectite/Corrensite 24.0 Sum 100

[0085] In FIG. 2, the swelling strain as a function of time observed during the experiment is shown. In the first days, swelling to approximately 15% swelling strain is observed in both oedometers 10 and 20. Without being bound to theory, it can be reasonably assumed to be purely clay swelling due to the temperature of 60 C. in the oven. At the first point of time T1 indicated in the FIG. 2 (about 27 day after start of the experiment), oedometer 10 was removed from the oven and placed in an environment with 20 C. One would expect then that ATG takes place and that swelling can be observed, and this is indeed the case since the swelling strain in the first oedometer 10 starts increasing again (cf. line with diamond marks in FIG. 2).

[0086] Next, the second oedometer 20 was removed from the 60 C. environment and placed in a 20 C. environment at a second point in time T2 (about 57 day after start of the experiment). However, with oedometer 20, its fluid was then replaced with a solution comprising 1 wt. % of a chemical inhibitor in water. The chemical inhibitor is a condensation product of lysine and succinic acid anhydride as described and produced according paragraphs 0055-0058 of US 2013/0289168 A1.

[0087] As can be seen from the FIG. 2, the ATG conversion in the second oedometer 20 is essentially suppressed by the solution of the chemical inhibitor, as hardly any increase in the swelling is recorded (cf. flat line with square marks in FIG. 2).

[0088] Standard thermogravimetric analysis (TGA) analysis later confirmed that there was no conversion of ATG in oedometer 20 (with chemical inhibitor), but with >90% conversion in oedometer 10 (with no inhibitor).

[0089] 2.2 Experiments 2-3

[0090] Similar experiments have been performed with different chemical inhibitors as shown in table 2:

TABLE-US-00002 TABLE 2 Inhibitors used in further experiments Exp. no. Chemical inhibitor Efficacy 2 polyacrylic acid (M.sub.n = 5000 g/mol) Comparable with experiment 1 3 diethylenetriaminepentaacetic acid Comparable with (DTPA) experiment 1

[0091] 2.3 Conclusion

[0092] As shown, the chemical inhibitors have been demonstrated unequivocally to function in their role of inhibiting the transformation of anhydrite to gypsum and the ensuing swelling from crystallization pressure. This means that if such kind of inhibitors are delivered to any affected material area, they will prevent swelling from this phenomenon.

[0093] It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricting.