A method and device for preparing a distributed karst model of a shallow stratum

Abstract

The present invention provides a preparation method and device for a distributed karst model of a shallow stratum, which relates to the field of geological exploration technology. The main purpose is to provide a research method and device that can be used for covering karst with distributed characteristics in view of the problem that the existing technology lacks research on the complexity of karst distribution, thereby providing a new research direction for engineering research in karst areas. The preparation method of the distributed karst model of the shallow stratum includes the following steps: A: confirming the total volume of the karst development zone, the karst volume rate and the karst development morphology; B: arranging the karst development zone that meets the above requirements by randomly mixing part of the model soil and dry ice in the model box, the outer peripheral side of the model stratum located in the model box is coated with model soil, and the ratio of the dry ice volume in the karst development zone of the mixed part to the total volume of the mixture of the part of the model soil and the dry ice meets the regional karst volume rate; C: distributed karst is formed where the randomly distributed dry ice is located.

Description

Technical Field

[0001] The invention relates to the technical field of geological exploration, and in particular to a preparation method and device for a shallow stratum distributed karst model. Background Art

[0002] Karst is a geological action of water on soluble rocks (carbonate rocks, gypsum, rock salt, etc.) mainly through chemical dissolution, supplemented by mechanical actions such as erosion, subsidence and collapse of flowing water, as well as a general term for the phenomena produced by these actions. The karst development morphology is complex and has weak regularity. According to the exposure form of bedrock, karst can be divided into exposed karst, covered karst, buried karst, etc. The karst adverse geology encountered in urban underground projects is mostly covered karst, whose bedrock is shallowly buried and covered with a certain thickness of loose deposits on the upper part. In the covered karst development area, due to the reciprocating movement of groundwater up and down the interface, the karst development of soluble rocks at the rock-soil interface is often strong, but the karst development morphology is different and is mainly small and medium-sized karst pipes, karst grooves, and karst troughs. Large centralized cavities are rare. The intensity of karst development usually gradually weakens with the increase of rock layer thickness.

[0003] In actual engineering, the characterization of karst development intensity is usually described by the hole-visibility ratio of drilling holes. The hole-visibility ratio in engineering survey is defined as the ratio of the sum of the number of drilling holes with karst (soil) caves in a certain area to the sum of the total number of drilling holes in the area. The hole-visibility ratio is only based on whether there is a rock and soil fault in the drilling hole as a judgment standard, which cannot reflect the development scale and shape of each karst cave body. In addition, it varies greatly due to the choice of drilling location, and cannot well reflect the volume of regional karst cave development.

[0004] When studying engineering problems in karst areas, the treatment of caves is mostly simplified to a single elliptical or circular cross-section hole, ignoring the complexity of the actual distribution of caves in karst areas. At the same time, in indoor model tests, inflatable air bags, high-temperature soluble wax, etc. are often used to simulate concentrated cavities, but this type of covered karst with distributed characteristics is rarely studied.

[0005] In order to facilitate the study of the distribution characteristics of karst, it is necessary to develop a processing method and a corresponding processing device that can simulate the model of this type of karst. Summary of the invention

[0006] The purpose of the present invention is to provide a method and device for preparing a distributed karst model of a shallow stratum, so as to solve the technical problem of lack of relevant research means in the prior art. The preferred technical scheme among the many technical schemes provided by the present invention can produce many technical effects as described below.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a distributed karst model of a shallow stratum, comprising the following steps:

[0009] A: Confirm the total volume of the karst development area, the karst volume ratio and the karst development morphology;

[0010] B: The karst development area meeting the above requirements is prepared by mixing part of the model soil and the volatilizable karst cavity filling material, and is arranged in the model box, and the outer peripheral side of the karst development area in the model box is coated with the model soil;

[0011] C: Distributed karst is formed where the volatile karst cavity fillings are located and the volatile karst cavity fillings are randomly distributed in the karst development area; the volume means and volume variances of all the volatile karst cavity fillings satisfy statistical laws.

[0012] The ratio of the volume of the volatile karst cavity filling material in the karst development zone formed by the above mixing to the total volume finally formed satisfies the regional karst volume ratio; in addition, on the basis of determining the morphology of a single cavity, the volume value of the volatile karst cavity filling material satisfies the statistical law (mainly referring to the volume mean and volume variance). The shallow stratum distributed karst model prepared under this condition can better simulate the required stratum, so as to facilitate the study of the corresponding geological conditions.

[0013] Based on the above technical solution, the present invention can also be improved as follows.

[0014] As a further improvement of the present invention, the karst volume rate for obtaining the karst model is determined according to the total volume of the karst development area and the total volume of the karst cavity formed after the volatilization of the volatile karst cavity filling material, including:

[0015] The karst volume ratio n=V_c / V;

[0016] Wherein, V_c is the total volume of the karst cavity formed after the volatile karst cavity filling material evaporates, and V is the total volume of the karst development zone.

[0017] As a further improvement of the present invention, the preparation steps of the karst development zone are as follows: take the required amount of model soil and volatile karst cavity filler, mix and stir evenly to obtain a mixture that conforms to the total volume of the karst development zone, and then arrange the obtained mixture at the location to be arranged according to the development morphology of the karst.

[0018] As a further improvement of the present invention, the volatile karst cavity filling material is dry ice.

[0019] As a further improvement of the present invention, the specific operation steps of step B are as follows:

[0020] S1: Filling the model box with model soil until the soil thickness is h1;

[0021] S2: insert at least two isolation plates above the soil and place the karst development area in the isolation space formed by the isolation plates, and fill the model soil to the space outside the isolation plates. At this time, the soil thickness is h2;

[0022] S3: remove the isolation plate and fill the model box with model soil to a specified height. At this time, the karst development area is covered by the model soil, and the soil thickness is h3; h1<h2<h3.

[0023] As a further improvement of the present invention, the isolation plate is an acrylic plate.

[0024] As a further improvement of the present invention, the model soil located above the karst development area needs to be filled and compacted.

[0025] As a further improvement of the present invention, a tunnel model is also arranged in the model soil below the karst development area.

[0026] As a further improvement of the present invention, the minimum distance between the edge of the tunnel model and the model box is not less than three times the inner diameter of the tunnel model.

[0027] The present invention also provides a preparation device for a distributed karst model of a shallow stratum, which is operated by any of the preparation methods for a distributed karst model of a shallow stratum described above, and comprises independently arranged model boxes and isolation plates, wherein an opening is provided at the upper end of the model box.

[0028] Compared with the prior art, the preparation method of the shallow stratum distributed karst model provided by the preferred embodiment of the present invention can use model soil and karst cavity fillers with good volatilization ability (such as dry ice, etc.) to simulate the karst cavity, so as to achieve the effect of constructing a karst development zone model: the process of dry ice volatilization at room temperature is, in a sense, a simulation of dissolution, which can better restore the formation process of the dissolution cavity in soluble rock. During configuration, the characteristics of regional karst random distribution can be simulated by stirring, and the control of karst development intensity can be achieved by controlling the volume rate of karst, so as to effectively simulate the covering type distributed karst adverse geological conditions often encountered in urban underground engineering, and better realize the randomness of karst distribution. At the same time, it also has the advantages of simple and convenient implementation and low material cost; in addition, the method can also realize the precise control of the karst development volume in the test through the regional karst volume rate; finally, the morphological size of the karst cavity prepared by this method has certain statistical characteristics, and the prepared karst development stratum is more in line with the actual karst geological conditions than the traditional preparation method. The present invention also provides a preparation device, which can better simulate actual geological conditions through a model box, an isolation plate and a tunnel model located in the box, thereby meeting preparation requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a schematic diagram of the use of the preparation device of the shallow stratum distributed karst model of the present invention;

[0031] Figure 2 yes Figure 1 Front section view of

[0032] Figure 3 yes Figure 1 side profile of;

[0033] Figure 4 yes Figure 1 A top cross-sectional view of

[0034] Figure 5A-Figure 5C It is another schematic diagram of the use of the preparation device of the shallow stratum distributed karst model of the present invention.

[0035] In the figure: 1. model box; 2. model soil; 3. isolation board; 4. dry ice; 5. tunnel model. DETAILED DESCRIPTION

[0036] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0037] In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc., are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0039] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0040] The present invention provides a method for preparing a distributed karst model of a shallow stratum. In practice, the shape of a karst cavity is obtained through engineering surveys, but the survey results usually have certain statistical characteristics. The present invention is expected to achieve effective simulation of the karst development in actual geology by preparing a distributed karst model that meets this statistical characteristic.

[0041] Embodiment 1:

[0042] The present invention provides a method for preparing a distributed karst model of a shallow stratum, comprising the following steps:

[0043] A: Confirm the total volume of the karst development area, the karst volume ratio and the karst development morphology;

[0044] B: a karst development area meeting the above requirements (i.e., the total volume of the karst development area, the karst volume ratio and the karst development morphology) is prepared by mixing part of the model soil and the volatilizable karst cavity filling material, and arranged in the model box 1, and the outer peripheral side of the karst development area in the model box 1 is coated with the model soil 2;

[0045] C: Distributed karst is formed where volatile karst cavity fillings are located and the karst cavity fillings are randomly distributed in the karst development area; the volume means and volume variances of all the volatile karst cavity fillings satisfy statistical laws.

[0046] The total volume of the karst development area and the development morphology of the karst need to be determined according to the model requirements and the relevant geological conditions to be simulated: Specifically, the scope, size, distribution morphology, regional karst volume rate n (i.e., cave volume rate), physical and mechanical parameters of the karst strata, etc. of the simulated karst development area are determined according to the engineering survey data, and then the size of the model box 1 used for model preparation and the total volume of the karst development area located inside the box are determined according to the above data. After determining the total volume, karst volume rate and development morphology of the karst development area, the volume of the model soil and the volume of the volatile karst cavity filling material required to construct the karst development area are obtained. By mixing a sufficient amount of volatile karst cavity filling material into the model soil that meets the above volume requirements, an effective simulation of the karst cavity can be achieved. At this time, the ratio of the volume of the volatile karst cavity filling material in the karst development area obtained by mixing to the total volume meets the regional karst volume rate requirements. Furthermore, on the basis of determining the single cavity morphology, the volume values ​​of various karst cavities formed by volatile karst cavity fillings satisfy statistical laws (mainly referring to their volume mean and volume variance).

[0047] At the same time, in the mixing process, the randomly distributed volatile karst cavity fillings can be used to simulate the random distribution characteristics of karst, which can more accurately reflect the adverse geological conditions of covered distributed karst commonly encountered in urban underground projects, and has the advantages of simple and convenient operation.

[0048] It should be noted that the above model soil needs to be configured according to the corresponding tunnel project or the surrounding rock grade of the geological conditions to be simulated, and its configuration method and configuration raw materials are all existing technologies and will not be repeated here. In addition, random distribution of karst can be achieved by random mixing.

[0049] As an optional implementation, the karst volume rate for obtaining the karst model is determined according to the total volume of the karst development area and the total volume of the karst cavity formed after the volatilization of the volatile karst cavity filling material, including:

[0050] Karst volume ratio n = V_c / V;

[0051] Among them, V_c is the total volume of the karst cavity formed after the volatilization of the volatile karst cavity fillings, and V is the total volume of the karst development area.

[0052] When preparing the karst development area, the required volatile karst cavity filling volume can be calculated according to the karst volume rate. The above V_c is determined according to the engineering survey results or research content, and refers to the total volume of the caves within the three-dimensional stratum range of the corresponding area. The precise control mentioned in the present invention refers to describing the regional geological karst development volume by the karst volume rate n.

[0053] As an optional implementation, the preparation steps in the karst development area are as follows:

[0054] The required amount of model soil 2 and volatile karst cavity filling material are placed in a mixing box and mixed evenly to obtain a mixture that conforms to the total volume of the karst development zone. The obtained mixture is then arranged at the position to be arranged according to the development morphology of the karst, that is, the area in the model used to form distributed karst.

[0055] As an optional embodiment, the volatilizable karst cavity filling material is dry ice 4. Dry ice 4 is solid carbon dioxide, which can volatilize into gas at room temperature and escape from the model soil layer 2. This volatilization process is a simulation of dissolution, which can better restore the formation process of the dissolution wall in the soluble rock. At the same time, the shape and size of the dissolution cavity formed after volatilization have certain statistical characteristics, and the prepared karst development stratum is more in line with the actual karst geological conditions.

[0056] Taking dry ice 4 as an example, since dry ice 4 evaporates quickly at room temperature, stirring should be avoided in a high temperature environment when preparing the karst development area to reduce the volatilization of solid carbon dioxide and affect the accuracy of the simulated karst volume rate. Similarly, step S2 should be performed as soon as possible after the karst development area is configured.

[0057] As an optional implementation, the specific operation steps of step B are as follows:

[0058] S1: Fill the model box 1 with model soil 2 until the soil thickness reaches h1;

[0059] S2: insert at least two isolation plates 3 above the soil and place the karst development area in the isolation space formed by the isolation plates 3, and fill the model soil 2 to the space outside the isolation plates 3. At this time, the soil thickness is h2;

[0060] S3: remove the isolation plate 3 and fill the model box 1 with the model soil 2 to a specified height. At this time, the karst development area is covered by the model soil 2, and the soil thickness is h3; h1<h2<h3.

[0061] As an optional implementation, the isolation plate 3 is an acrylic plate.

[0062] As an optional implementation, the model soil 2 located above the karst development area needs to be filled and compacted.

[0063] As an optional implementation, a tunnel model 5 is also provided in the model soil 2 below the karst development area to better simulate the urban underground geological conditions.

[0064] In order to ensure the accuracy and scientificity of the model, and taking into account the actual construction requirements of the tunnel function, the size of the model box 1 needs to be adjusted according to the location of the tunnel model 5. Generally speaking, it is necessary to ensure that the minimum distance between the edge of the tunnel model 5 and the model box 1 is not less than three times the inner diameter of the tunnel model 5.

[0065] Compared with the prior art, this method has the following advantages:

[0066] 1. By using dry ice 4 to simulate karst cavity filling (i.e., molten rock part), the dry ice 4 is mechanically mixed with the surrounding rock and soil to realize the random distribution of regional karst. This provides an experimental simulation method for the unfavorable geological conditions of covered distributed karst commonly encountered in urban underground projects, which better realizes the randomness of karst distribution. The implementation method is simple and convenient, and the material cost is low.

[0067] 2. The concept of karst volume ratio is proposed for covered distributed karst. The range of the experimental simulation section is determined by determining the development range of the karst section of the prototype project. The precise control of the karst development volume in the experiment is achieved through the regional karst volume ratio.

[0068] 3. In the test preparation method, the rock mass that produces dissolution is simulated using dry ice 4. Dry ice 4 will gradually evaporate into gas at room temperature and escape from the model soil 2 layer. Its volatilization process is a simulation of dissolution in a sense. This method better restores the formation process of the dissolution cavity in the soluble rock.

[0069] 4. The karst cavity formed in the experimental preparation method has certain statistical characteristics in shape and size, and the prepared karst development strata are more in line with the actual karst geological conditions.

[0070] Embodiment 2:

[0071] The present invention also provides a preparation device for a distributed karst model of a shallow stratum, which is a preparation device operated by any of the above-mentioned methods for preparing a distributed karst model of a shallow stratum, and includes an independently arranged model box 1 and an isolation plate 3. An opening is provided at the upper end of the model box 1, and the corresponding model soil 2 and karst development area can be placed in the model box 1 through the opening.

[0072] The karst model prepared by the device can have a variety of different forms. The form of the karst model can be adjusted and transformed according to the engineering prototype and research content, including but not limited to uniform layered distribution. Taking uniform layered distribution as an example, the use of the karst model preparation device is as follows: Figure 1-4 shown.

[0073] First, it is necessary to determine the scope, size, distribution pattern, regional karst volume rate n, physical and mechanical parameters of karst formations, and size of the test model box 1 based on the engineering survey data. When the engineering survey involves tunnel engineering, the size of the model box 1 needs to be adjusted according to the tunnel engineering, and generally the distance from the tunnel side wall to the box edge is not less than 3 times the tunnel diameter.

[0074] In this embodiment, the size of the model box 1 can be (2.5m (length) × 1m (width) × 2.5m (height)). The range, size and distribution form of the karst development area are determined according to the engineering survey data or research content. In this embodiment, the karst can be developed in a uniform layered manner, with a development range length of L = 2.5m, W = 1m, and H = 0.4m. The total range of the karst development area V = L × W × H = 1m is determined by calculation. 3 , taking karst volume ratio n = 5%, V_c = 0.05m 3 , the top soil thickness is 1m, the karst filling (4) uses columnar dry ice 4, according to the statistical parameters: μ = 5cm 3 (volume mean), σ=4 (volume variance) for preparation.

[0075] For the convenience of determination, the model box 1 may be marked in advance according to relevant parameters.

[0076] Subsequently, the volume of the model soil 2 and the volume of dry ice 4 (solid carbon dioxide) required for the simulation area are determined based on the above information, and the dry ice 4 that meets the requirements is prepared in the factory; the model soil 2 and dry ice 4 in the required amounts are placed in a mixing box for mixing and stirring for later use.

[0077] During preparation, first fill the model soil 2 in the model box 1 to the karst development level (if there is a tunnel model 5, the tunnel model 5 is located in the model soil 2), then insert the isolation plate 3 made of acrylic material into the model soil 2 and reserve the karst development area, arrange the aforementioned fully configured dry ice 4 and model soil 2 mixture, and then fill and compact until the dry ice 4 and model soil 2 mixture is completely filled, then remove the isolation plate 3 and continue to fill the model box 1 with a covering soil layer (the covering soil layer refers to the remaining model soil 2, of course, it can also be other soil that meets the required geological conditions), and compact it, and after the dry ice 4 is completely volatilized, a karst cavity is formed in the soil layer.

[0078] It should be noted that karst preparation should be carried out immediately after the model soil 2 and dry ice 4 are mixed to reduce the volatilization of solid carbon dioxide and avoid affecting the accuracy of the model karst volume rate.

[0079] Generally speaking, in order to save time and reduce the volatilization of dry ice 4, when the model soil 2 and dry ice 4 are mixed and stirred, the model soil 2 should be filled into the model box 1 to the bottom mark of the karst development layer (h1) and the acrylic isolation plate 3 should be inserted. Then, the mixture of the stirred model soil 2 and dry ice 4 should be buried to the top elevation of the isolation area (h2); then the acrylic isolation plate 3 should be removed and the remaining model soil 2 should be buried to the specified elevation (h3).

[0080] After the dry ice 4 is completely volatilized, a karst cavity can be formed in the soil layer of the model box 1.

[0081] When the karst model is distributed in other ways, the use of the karst model preparation device is shown in the following figure. Figure 5A , 5B and 5C.

[0082] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a distributed karst model of a shallow stratum, characterized in that: The following steps are involved: A: Confirm the total volume of the karst development area, the karst volume ratio and the karst development morphology; B: The karst development area meeting the above requirements is prepared by mixing part of the model soil and the volatilizable karst cavity filling material, and is arranged in the model box, and the outer peripheral side of the karst development area in the model box is coated with the model soil; C: Distributed karst is formed where the volatile karst cavity fillings are located and the volatile karst cavity fillings are randomly distributed in the karst development area; the volume means and volume variances of all the volatile karst cavity fillings satisfy statistical laws.

2. The method for preparing a shallow stratum distributed karst model according to claim 1, characterized in that: The karst volume rate of the karst model is determined according to the total volume of the karst development area and the total volume of the karst cavity formed after the volatilization of the volatile karst cavity filling material, including: The karst volume ratio n=V_c / V; Wherein, V_c is the total volume of the karst cavity formed after the volatile karst cavity filling material evaporates, and V is the total volume of the karst development zone.

3. The method for preparing a distributed karst model of a shallow stratum according to claim 1, characterized in that: The preparation steps of the karst development area are as follows: The required amount of model soil and volatilizable karst cavity filling material are mixed and stirred evenly to obtain a mixture that conforms to the total volume of the karst development zone, and then the obtained mixture is arranged at the location to be arranged according to the development morphology of the karst.

4. The method for preparing a distributed karst model of a shallow stratum according to claim 1, characterized in that: The volatile karst cavity filling material is dry ice.

5. The method for preparing a distributed karst model of a shallow stratum according to claim 1, characterized in that: The specific operation steps of step B are as follows: S1: Filling the model box with model soil until the soil thickness is h1; S2: insert at least two isolation plates above the soil and fill the karst development area into the isolation space formed by the isolation plates, and fill the model soil into the space outside the isolation plates. At this time, the soil thickness is h2; S3: remove the isolation plate and fill the model box with model soil to a specified height. At this time, the karst development area is covered by the model soil, and the soil thickness is h3; h1<h2<h3.

6. The method for preparing a distributed karst model of a shallow stratum according to claim 5, characterized in that: The isolation plate is an acrylic plate.

7. The method for preparing a distributed karst model of a shallow stratum according to claim 5, characterized in that: The model soil located above the karst development area needs to be filled and compacted.

8. The method for preparing a shallow stratum distributed karst model according to any one of claims 1 to 7, characterized in that: A tunnel model is also arranged in the model soil below the karst development zone.

9. The method for preparing a distributed karst model of a shallow stratum according to claim 8, characterized in that: The minimum distance between the edge of the tunnel model and the model box is not less than three times the inner diameter of the tunnel model.

10. A preparation device for a distributed karst model of a shallow stratum, characterized in that: A simulation device operated by the preparation method of a shallow stratum distributed karst model according to any one of claims 1 to 9, the device comprising independently arranged model boxes and isolation plates, wherein the upper end of the model box is provided with an opening.

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