Preparation method and preparation device of fractured rock mass similar material for simulation analysis

Abstract

The invention relates to the technical field of rock mass detection, and particularly discloses a preparation method and a preparation device of a fractured rock mass similar material for simulation analysis. The method comprises the following steps: (S1) obtaining performance data of fissure zone rock on an engineering site through in-situ testing, then calculating similar physical parameters required in a simulation test through a similarity criterion, and preparing fissure zone similar material aggregate and slurry; (S2) filling the aggregate into a mold, and pumping the slurry to prepare a fissure similar test piece. And (S3) testing performance data of the test piece, comparing the performance data with the similar physical parameters in the step (S1) to obtain optimal pumping parameters, and preparing the fractured rock mass similar material on the basis of the optimal pumping parameters. According to the preparation method of the fractured rock mass similar material, the simulated rock mass similar material is closer to actual engineering, and the problem that the authenticity and reliability of a physical simulation test are affected due to the fact that the rock mass similar material manufactured in the prior art cannot obtain an accurate simulation result for the fractured rock mass is effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of fractured rock mass simulation analysis and detection, and in particular to a method for preparing fractured rock mass similar material for simulation analysis and a preparation device thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The strength of cracks in rocks has an important influence on the mechanical properties of the entire rock, such as compression and tension. The mechanical and permeability characteristics of cracks have a significant impact on the accuracy of physical simulation tests. At the engineering site, the mechanical parameters and permeability characteristics of cracks can be obtained by obtaining, collecting, and monitoring information on cracked rock mass. However, away from the engineering project site, there is a lack of technology to prepare materials similar to rock cracks, especially when it comes to mechanical strength and permeability.

[0004] For example, the patent document with application number 202310881670.8 discloses a preparation method for a similar simulated rock formation sample with joints and fissures. It uses a sample preparation box and two side plugs to simulate the horizontal joints and vertical joints and fissures of the rock formation, thereby preparing a similar simulated rock formation sample containing joints and fissures. It can simulate the horizontal joints and vertical joints and fissures of the rock formation to conduct mechanical experimental research on similar simulated rock formation samples containing joints and fissures. However, this technology only maintains consistency with the rock in terms of occurrence, and other mechanical consistency is not guaranteed, which affects the accuracy of the physical simulation test.

[0005] For another example, the patent document with application number 202110563814.6 discloses a mold and forming method for making true triaxial specimens of deep rock-like materials, which solves the problems of poor single-sided compaction uniformity, low precision, the need for re-grinding after sampling, large demolding disturbance, and difficulty in making true triaxial specimens in the prior art. However, in reality, after complex geological actions, rocks will form structural surfaces inside. The above-mentioned patented technology simulates the production of true triaxial specimens of deep rock-like materials, and cannot simulate materials similar to rock cracks.

[0006] In summary, although the existing technology has made certain progress in the preparation of rock similarity models, the produced rock similarity materials cannot obtain accurate simulation results for fractured rock masses, affecting the authenticity and reliability of physical simulation experiments. Summary of the invention

[0007] In view of the above problems, the present invention proposes a method and a device for preparing fractured rock mass similar materials for simulation analysis, wherein the fractured rock mass similar materials prepared by the method are closer to actual engineering, and the accuracy of the test results and the practical application value are improved. Specifically, the technical solution of the present invention is as follows.

[0008] First, the present invention provides a method for preparing similar materials of fractured rock mass for simulation analysis, comprising the following steps: (S1) Obtain the compressive strength and permeability data of the rock in the fracture zone at the engineering site through in-situ testing, and then calculate the similarity parameters required for the simulation test based on these data and the similarity criterion, and configure the slurry and aggregate required for the preparation of similar materials in the fracture zone based on these parameters.

[0009] (S2) Filling the aggregate of step (S1) into a mold until the mold is filled in a natural stacking state, and then pumping the slurry of step (S1) into the mold until it is full, and curing and demolding after completion to obtain a crack-similar specimen. The crack-similar specimens under different pumping parameters are prepared in the same manner and set aside.

[0010] (S3) The compressive strength and permeability of each of the similar fracture specimens obtained in step (S2) are tested, and then compared with the similar parameters of step (S1) after calculation using a similarity criterion, and the pumping parameters of the similar fracture specimen that are closest to the similar parameters are used as the optimal pumping parameters for standby use.

[0011] (S4) A similar material of the base rock of the engineering site of step (S1) is configured according to the similarity criterion, and then the material is laid in a model box of the physical simulation test. Then, the slurry configured in step (S1) is injected into the model box using the optimal pumping parameters of step (S3) until it is full, and after completion, curing and demolding are performed to obtain the similar material of the fractured rock mass.

[0012] Furthermore, in step (S1), the slurry includes cement binder and water, and the method for determining the slurry and aggregate is: the slurry and aggregate are mixed evenly to form a cement-based material, which is poured into a mold, hardened and demolded, and then subjected to standard curing for 24 to 36 hours to obtain a test piece. Then, the ratio of the cement binder, water and aggregate, and the aggregate particle size are changed, and the test pieces are prepared using the above method, and the compressive strength and permeability of these test pieces are tested. If the difference between the test results and the compressive strength and permeability of the similar parameters in step (S1) is within 2%, the corresponding cement binder and water can be used as the slurry of step (S1), and the corresponding aggregate can be used as the aggregate of step (S1).

[0013] Furthermore, in step (S2), the top port of the mold is sealed and the slurry is injected until the injection flow rate is less than the set value, and the slurry is considered to have filled the gap in the mold, at which time the injection is stopped. Optionally, the set value is 4-6m 3 / h.

[0014] Furthermore, in step (S2), the inner surface of the mold is coated with a release agent to facilitate demoulding after the curing is completed to obtain the crack-similar test piece. Similarly, in step (S4), the inner surface of the model box is also coated with a release agent.

[0015] Furthermore, in steps (S2) and (S4), the curing time is 1 to 2 days.

[0016] Furthermore, in step (S2), the mold includes any one of a standard mold and a scaled mold.

[0017] Furthermore, in step (S2), the pumping parameters include pumping frequency (n) and pumping time (t). The pumping frequency (n) refers to the number of pumping times per minute when pumping the slurry.

[0018] Furthermore, in step (S4), the similar materials of the base rock at the engineering site include the following components: quartz sand, cement, barite powder, talcum powder, silicone oil and water. The proportion of each component can be selected according to actual needs.

[0019] Secondly, the present invention provides a preparation device for similar materials of fractured rock mass for simulation analysis, comprising: a mold, a rotating table, a cover body, a rotary joint, a delivery pump, a slurry tank and a return pipe. Wherein: the mold is detachably fixedly connected to the rotating table so as to rotate with the rotating table. The cover body is detachably covered on the top opening of the mold, the rotary joint is rotatably connected to the grouting port on the cover body, and the rotary joint, the delivery pump and the slurry tank are connected in sequence. The bottom liquid outlet of the mold is rotatably connected to the return pipe, the other end of the return pipe is connected to the slurry tank, and a screen for blocking the aggregate is provided in the liquid outlet.

[0020] Furthermore, a flow monitoring element is provided on the grouting pipe between the rotary joint and the delivery pump for monitoring flow changes in the grouting pipe.

[0021] Furthermore, the flow monitoring element is connected to a control system, and the control system is connected to the delivery pump to control the grouting pressure of the delivery pump.

[0022] Furthermore, the rotating table is an annular structure, and the liquid return pipe passes through the annular structure and is rotatably connected to the bottom liquid outlet of the mold.

[0023] Furthermore, a flange is fixed on the lower side wall of the mold, and an annular tray is fixed on the upper surface of the rotating table. The flange and the annular tray are detachably connected via fasteners, and the bottom surface of the mold is in a suspended state.

[0024] Compared with the prior art, the present invention has at least the following beneficial technical effects: (1) The method of the present invention prepares fracture-like specimens based on the compressive strength and permeability data of the fracture zone rock at the engineering site, so that the simulated rock fracture-like materials are closer to the actual rocks at the engineering site, effectively overcoming the problem that the rock mass similar materials produced by traditional technology cannot obtain accurate simulation results for fractured rock mass, affecting the authenticity and reliability of physical simulation tests. (2) The present invention also provides a preparation device for fractured rock mass similar materials, filling the gap in the preparation device for fractured rock similar materials. In addition, the mold of the present invention can also rotate, which solves the problem of uneven distribution of similar material slurry during the infiltration process and improves the quality of the prepared fractured rock similar materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 The compressive strength-strain curve of the crack-similar specimen prepared in the following Example 1.

[0027] Figure 2 This is a test diagram of the permeability coefficient of a fracture-similar specimen prepared in the following Example 1.

[0028] Figure 3 Schematic diagram of the structure of the preparation device of the fracture-similar material used for simulation analysis in the following Example 2.

[0029] Figure 4 Schematic diagram of the funnel structure in the preparation device of fracture-similar materials in the following Example 2.

[0030] Above Figure 3 and Figure 4 The numbers in the figure represent: 1-mold, 2-rotating table, 3-cover body, 4-rotating joint, 5-delivery pump, 6-slurry tank, 7-return pipe, 8-flow monitoring element, 9-flange, 10-ring tray, 11-funnel structure, 12-servo motor. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0033] For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or component needs to have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0034] The method for preparing similar materials of fractured rock mass for simulation analysis and the preparation device thereof are now further described in conjunction with the accompanying drawings and specific embodiments of the specification.

[0035] Embodiment 1: Taking the "water seal simulation test project of surrounding rock stress seepage coupling field of the whole life cycle of underground storage in caves" as the research object, the method proposed in the present invention is further explained to prepare similar materials of fractured rock mass for simulating and analyzing the research object. Specifically, the preparation process includes the steps of: (S1) In-situ testing / field testing was used to obtain the compressive strength and permeability data of the fracture zone of the rock at the project site: compressive strength = 106.19 MPa, permeability coefficient = 1.9423×10 -7 m / s. Then, the scale of similar materials is calculated according to the fluid-solid coupling similarity criterion, and the geometric similarity scale (C l =100) in the similarity simulation criterion under the three-dimensional solid-fluid coupling (Reference: Similarity Simulation Theory and Method of Three-Dimensional Solid-Fluid Coupling, Hu Yaoqing et al., Journal of Liaoning Technical University (Natural Science Edition), 2007), and determine the model similarity material scale. The specific results are shown in Table 1 below.

[0036] Table 1

[0037] According to the parameters in Table 1 and the references mentioned above, the similar parameters required for the simulation test are calculated as follows: compressive strength = 1.0619 MPa, permeability coefficient = 1.9423×10 -8 m / s.

[0038] (S2) Based on the above similar parameters, white silicate cement, sand and gravel, and water are used as raw materials to prepare similar materials for fracture zones. Specifically, the white silicate cement, sand and gravel, and water are mixed and stirred evenly, then poured into a mold and demolded after hardening and forming, and then placed in a standard curing box (temperature maintained at 20±2°C, humidity maintained between 95~97%) for curing for 24 hours. After completion, the compressive strength and permeability coefficient of the specimens obtained are tested. Through orthogonal experiments, it is found that when the mass ratio of white silicate cement, water, and sand and gravel is 4.1:3.3:3.6, and the sand and gravel particle size is continuously graded between 1~1.5cm, the compressive strength and permeability coefficient of the specimens obtained are respectively the same as the similar parameters (compressive strength = 1.0619MPa, permeability = 1.9423×10 -8 m / s) the corresponding index difference values ​​are all within 2%. Therefore, the mixture formed by the mass ratio of the white silicate cement to water of 4.1:3.3 is used as slurry, and the sand and gravel with a particle size of 1-1.5 cm and continuous grading is used as aggregate for standby use.

[0039] (S4) Testing the compressive strength and permeability coefficient of each of the similar fracture specimens prepared in the above step (S3), and recording the test results of each similar fracture specimen (as shown in Table 2 below). Figure 1 is the compressive strength-strain curve of the similar crack specimen obtained when the pumping frequency n=2, Figure 2 This is the permeability coefficient test diagram of a similar specimen to this crack.

[0040] Table 2

[0041] (S5) Compare the performance test results (compressive strength, permeability coefficient) of similar specimens of each fracture in Table 2 with the similar parameters (compressive strength = 1.0619 MPa, permeability coefficient = 1.9423×10 -8 m / s) and the pumping parameters corresponding to the fracture-like specimen closest to the parameters are taken as the optimal pumping parameters. It can be seen that when the pumping frequency n=10 and the pumping time t=5min, the performance of the prepared fracture-like specimen (compressive strength=1.13 MPa, permeability coefficient=1.6402×10 -8 m / s) is closest to the above similar parameters. Therefore, the optimal pumping parameters are: pumping frequency n=10, pumping time t=5min.

[0042] (S6) According to the similarity criterion, a material with similar physical and mechanical properties to the base rock at the engineering site is configured (referred to as material a, which is formed by mixing the following components: 850 parts by weight of quartz sand, 159 parts by weight of 42.5 ordinary Portland cement, 350 parts by weight of barite powder, 420 parts by weight of talcum powder, 70 parts by weight of silicone oil, and 200 parts by weight of water), and then the material a is laid in the model box of the physical simulation test. Then, the slurry configured in step (S2) is pumped into the model box using the optimal pumping parameters of step (S5) until it is full (the mass ratio of the material a to the slurry is 10:1), and then the model box and the materials therein are cured at room temperature for 2 days, and the fractured rock mass similar material is obtained after demolding. The compressive strength is measured to be 1.1254 MPa, and the permeability coefficient is 1.8526×10 -8 m / s. It can be seen that the compressive strength error rate between the fractured rock mass similar material prepared by the method of this embodiment and the compressive strength error rate of the rock at the project site is only 5.98%, and the permeability error rate is only 4.62%. The error rate of fractured rock mass similar materials prepared by traditional methods is as high as more than 10%. Therefore, the rock mass similar material prepared by the method of this embodiment for simulation analysis is closer to the actual project, which effectively improves the accuracy of the test results and the practical application value.

[0043] refer to Figure 3 , an example of a preparation device for similar materials of fractured rock mass for simulation analysis is provided, comprising: a mold 1, a rotating table 2, a cover 3, a rotating joint 4, a delivery pump 5, a slurry box 6 and a liquid return pipe 7. Specifically: the mold 1 is a cylindrical structure with openings at both ends, and the rotating table 2 is an annular structure. A fixedly connected flange 9 is sleeved on the lower side wall of the mold 1, and an annular tray 10 is fixed on the upper surface of the rotating table 2. The flange 9 and the annular tray 10 are detachably fixedly connected by fasteners such as bolts, and the bottom surface of the mold 1 is in a suspended state, so that the mold 1 can be detachably connected to the rotating table 2. The rotating table 2 can adopt existing equipment, which can rotate horizontally under the action of a driving mechanism, thereby driving the mold 1 to rotate synchronously. The mold 1, the rotating table 2, the flange 9, and the annular tray 10 are arranged along the same vertical axis.

[0044] The cover body 3 is detachably covered on the top opening of the mold 1. For example, the outer side wall of the upper port of the cover body 3 has an external thread, and the cover body 3 is threadedly connected to the top opening of the mold 1. In a more preferred embodiment, a sealing rubber ring is provided between the cover body 3 and the top surface of the mold 1 to prevent leakage of slurry during grouting. The rotary joint 4 is rotatably connected to the grouting port at the center of the upper surface of the cover body 3 so as to grout into the inner cavity of the mold 1. The other end of the rotary joint 4, the delivery pump 5, and the slurry tank 6 are connected in sequence through a grouting pipeline, and the rotary joint 4 is detachably connected to the delivery pump 5. The delivery pump 5 can be a centrifugal pump, etc., and can be powered by a servo motor 12 to deliver slurry. A liquid filling port can also be provided on the slurry tank 6 to supplement the slurry of the fracture-similar material.

[0045] The bottom of the mold 1 has a liquid outlet, and a screen is provided in the liquid outlet to prevent the aggregate from leaking out. The liquid return pipe 7 passes through the rotating table 2 of the annular structure from below and is rotatably connected to the liquid outlet. The other end of the liquid return pipe 7 is connected to the slurry tank 6 to recover the slurry of the fracture-like material leaking from the liquid outlet when grouting into the mold 1, and can more fully discharge the gas in the mold 1, so that the slurry of the fracture-like material is fully distributed and filled in the mold 1, avoiding the problem that the residual gas in the mold 1 affects the simulation of the real state of the internal fractured rock by the prepared rock-similar material.

[0046] refer to Figure 4 The slurry inlet end of the liquid return pipe 7 is provided with a funnel structure 11, the larger end of which is rotatably connected to the bottom end of the mold 1 and is coaxially arranged with the liquid outlet. Specifically, the edge of the larger end of the funnel structure 11 is provided with an annular slider, which is embedded in the annular guide rail provided at the bottom of the mold 1, so that the rotation of the mold 1 does not affect the liquid return pipe 7. The other end of the liquid return pipe 7 is connected to the inlet at the top of the slurry tank 6.

[0047] When in use, first turn on the delivery pump 5 to inject the fracture-similar material slurry (as shown in Example 1) in the slurry box 6 through the rotary joint 4 into the mold 1 filled with aggregate (as shown in Example 1), the inner wall of which is coated with a release agent. At the same time, drive the mold 1 to rotate so that the fracture-similar material slurry in the mold 1 is more evenly distributed, thereby improving the quality of the prepared fractured rock-similar material. As more slurry is injected, the excess slurry is discharged from the liquid outlet at the bottom of the mold 1 under the action of the grouting pressure and then enters the slurry box 6 for recovery. When the flow reading at the slurry injection end of the mold 1 is less than the set value (such as 4m 3 / h、5m 3 / h、6m 3 / h, etc.) to stop grouting. To this end, a flow monitoring element 8 can be set on the grouting pipeline between the rotary joint 4 and the delivery pump 5. At the same time, the flow monitoring element 8 is connected to the control system, and the control system is connected to the delivery pump 5 to control the grouting flow of the delivery pump 5 to ensure that the above-mentioned slurry injection value is met.

[0048] After the above grouting work is completed, the flange 9 of the mold 1 is disassembled from the annular tray 10, and then the bottom of the mold 1 is quickly covered with a sealed bottom cover to prevent the slurry from flowing out, and then the cover body 3 is removed from the mold 1, and the mold 1 together with the material therein is transferred to a curing box for standard curing, and after curing to a predetermined age (1-2 days), demolding is performed to obtain the fractured rock mass similar material. The above fractured rock mass similar material preparation device of this embodiment realizes the implementation of the above fractured rock mass similar material process, which fills the gap in the actual preparation of fractured rock similar material.

[0049] Finally, it should be noted that any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. Although the above describes the specific implementation of the present invention in conjunction with the drawings, it is not a limitation of the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A method for preparing similar materials of fractured rock mass for simulation analysis, characterized in that: The steps include: (S1) Obtain the compressive strength and permeability data of the rock in the fracture zone of the project site through in-situ testing, and then calculate the similarity parameters required for the simulation test based on these data and similarity criteria, and configure the slurry and aggregate required for the preparation of similar materials in the fracture zone based on these parameters; (S2) filling the aggregate of step (S1) into a mold until the mold is filled in a natural stacking state, and then pumping the slurry of step (S1) into the mold until the mold is filled, and curing and demoulding after completion to obtain a similar crack specimen; using the same method to prepare similar crack specimens under different pumping parameters for later use; (S3) testing the compressive strength and permeability of each of the similar fracture specimens obtained in step (S2), and then comparing them with the similar parameters of step (S1) after calculation using a similarity criterion, and taking the pumping parameters of the similar fracture specimen closest to the similar parameters as the optimal pumping parameters for standby use; (S4) configuring similar materials of the base rock of the engineering site in step (S1) according to similarity criteria, and then laying the material in a model box of a physical simulation test; then injecting the slurry configured in step (S1) into the model box using the optimal pumping parameters of step (S3) until it is full, and after completion, performing curing and demoulding to obtain similar materials of the fractured rock mass.

2. The method for preparing similar materials of fractured rock mass for simulation analysis according to claim 1, characterized in that: In step (S1), the slurry includes cement binder and water, and the method for determining the slurry and aggregate is: the slurry and aggregate are mixed evenly to form a cement-based material, which is poured into a mold, hardened and demolded, and then standardly cured for 24 to 36 hours to obtain a test piece; then the ratio of the cement binder, water and aggregate, and the aggregate particle size are changed, and the test pieces are prepared by the above method, and the compressive strength and permeability of these test pieces are tested. If the difference between the test results and the compressive strength and permeability in the similar parameters of step (S1) is within 2%, the corresponding cement binder and water can be used as the slurry of step (S1), and the corresponding aggregate can be used as the aggregate of step (S1).

3. The method for preparing similar materials of fractured rock mass for simulation analysis according to claim 1, characterized in that: In step (S2), the top port of the mold is sealed and the slurry is injected until the injection flow rate is less than a set value, and then the injection is stopped; or the set value is 4-6m 3 / h.

4. The method for preparing similar materials of fractured rock mass for simulation analysis according to claim 1, characterized in that: In step (S2), the inner surface of the mold is coated with a release agent; or, in step (S4), the inner surface of the model box is also coated with a release agent.

5. The method for preparing similar materials of fractured rock mass for simulation analysis according to claim 1, characterized in that: In steps (S2) and (S4), the curing time is 1 to 2 days; or, in step (S2), the pumping parameters include pumping frequency and pumping time.

6. The method for preparing similar materials of fractured rock mass for simulation analysis according to any one of claims 1 to 5, characterized in that: In step (S4), the similar materials of the base rock at the engineering site include the following components: quartz sand, cement, barite powder, talcum powder, silicone oil and water.

7. A device for preparing similar materials of fractured rock mass for simulation analysis, characterized in that: include: A mold, a rotating table, a cover body, a rotating joint, a delivery pump, a slurry tank and a return pipe; wherein: the mold is detachably fixedly connected to the rotating table; the cover body is detachably covered on the top opening of the mold, the rotating joint is rotatably connected to the grouting port on the cover body, and the rotating joint, the delivery pump and the slurry tank are connected in sequence; the bottom liquid outlet of the mold is rotatably connected to the return pipe, the other end of the return pipe is connected to the slurry tank, and a screen is provided in the liquid outlet for blocking the aggregate in the preparation method described in any one of claims 1 to 6.

8. The device for preparing similar materials of fractured rock mass for simulation analysis according to claim 7, characterized in that: A flow monitoring element is provided on the grouting pipeline between the rotary joint and the delivery pump; the flow monitoring element is connected to a control system, and the control system is connected to the delivery pump.

9. The device for preparing similar materials of fractured rock mass for simulation analysis according to claim 7, characterized in that: The rotating platform is an annular structure, and the liquid return pipe passes through the annular structure and is rotatably connected to the bottom liquid outlet of the mold.

10. The device for preparing similar materials of fractured rock mass for simulation analysis according to claim 7, characterized in that: A flange is fixed on the lower side wall of the mold, and an annular tray is fixed on the upper surface of the rotating table. The flange and the annular tray are detachably connected via fasteners, and the bottom surface of the mold is in a suspended state.

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