Method for preparing layered structure of rock-like material physical model of roadway cement mortar

Abstract

A layered structure roadway cement mortar physical model preparation method of rock-like material belongs to the field of rock mass mechanics and rock engineering, and steps are as follows: 1. According to the engineering site situation and the predicted size, a mold is made, and a preset roadway hole is drilled on the required unit plate in advance, and then combination is carried out; 2. The roadway model is made, and after the mold combination is completed, it is inserted along the opposite preset roadway hole, and the combined mold is prepared; 3. The combined mold is placed on the telescopic support device; 4. The inner wall of the mold and the outside of the roadway model are coated with release agent, and the rock-like material is poured layer by layer, the existence of layered joints is highlighted, and the surface is scraped after vibration and compaction; 5. Demoulding and curing, and the layered structure roadway cement mortar physical model is obtained. The preset roadway hole on the mold ensures the similarity between the poured physical model and the deep metal mine layered rock roadway; the model prepared by using cement mortar reduces the difficulty and cost of obtaining the layered rock.

Description

Technical Field

[0001] This invention belongs to the field of rock mechanics and rock engineering, and specifically relates to a method for preparing a physical model of cement mortar for layered roadways made of rock-like materials. Background Technology

[0002] Layered rock masses are widely distributed in nature. With the continuous development of underground engineering in my country, many tunnels, caverns, and roadways are constructed through layered rock masses. The structural characteristics of layered rock masses are mainly manifested in poor overall rock mass integrity, well-developed joints and fissures, and the significant influence of bedding parameters on the stability of the surrounding rock, exhibiting obvious anisotropic characteristics.

[0003] During excavation, tunnels are prone to disasters such as arch bending and fracture, spalling and rockfall, threatening the safety of on-site personnel and the quality of the project, and posing significant challenges to construction and subsequent operation. Currently, the failure mechanism of layered rock masses is not fully understood, especially in deep metal mines where the surrounding rock of layered tunnels is unclear. The relationship between its failure characteristics and stress conditions, layered rock mass structural parameters, and blasting disturbance is ambiguous, resulting in poor support effectiveness. Therefore, in-depth research into the failure mechanism of layered rock tunnels under the coupled effects of high ground stress and blasting disturbance is of significant engineering importance for disaster prevention and control and optimization of support parameters in deep tunnels.

[0004] In-situ testing, field sampling, and laboratory experiments are important methods for studying the physical and mechanical properties of rock masses. In-situ testing requires sophisticated equipment and is greatly affected by the site conditions; layered rock masses have poor integrity, making successful field sampling difficult. Therefore, laboratory experiments are an effective way to study the failure mechanism of layered rock masses, and preparing a physical model of layered structure roadway cement mortar resembling rock material is the most important step in this process.

[0005] Due to the unique structure of layered rock masses, there is currently no method for preparing physical models of rock-like materials that can accurately and effectively simulate layered tunnel structures. Patents CN109049274A and CN205262824U disclose a method for preparing layered rock mass samples and a mold for preparing them, both using standard parts for sample preparation. Patent CN211718278U uses an adhesive bonding material to bond spherical particles to simulate layered rock masses. The device in patent CN216847152U can prepare layered rock mass models with circular holes. Patent CN111175105A, "A Method for Preparing Layered Rock Mass Rock-like Samples," discloses a method for preparing layered rock mass rock-like samples. This method uses a soluble material as a mold to cast the layered rock mass rock-like sample, without pre-reserving tunnel openings, resulting in a relatively complete layered rock mass rock-like sample. The methods and apparatus disclosed in the above patents have failed to prepare physical models of layered rock masses containing semi-circular arched tunnel holes, which differ from layered rock mass tunnel engineering and have certain limitations.

[0006] Currently, there are certain difficulties in preparing physical models of layered rock masses using similar materials. Most methods involve bonding finite element plates with cementing materials or fabricating small-sized layered rock mass models. This means that methods for preparing physical models of larger-sized, porous layered rock masses are even more lacking. Therefore, in order to conduct indoor experiments on the failure mechanism of surrounding rock in layered rock tunnels, there is a need to invent a physical model preparation method that can better simulate the actual environment of layered rock tunnels. Furthermore, given that the dip angle of layered joints in actual engineering environments is not perfectly vertical or horizontal, this method should not only have the basic function of layered joint casting and molding but also be able to accommodate the fabrication of layered joints with different dip angles. It should be noted that existing patents have not fully met the above requirements. This invention will fill these functional gaps, providing a better preparation method for indoor model testing of the failure mechanism of surrounding rock in deep metal mine layered rock tunnels. Summary of the Invention

[0007] To address the problem that current indoor physical models of layered rock masses cannot accurately simulate actual engineering conditions, this invention provides a method for preparing a physical model of a layered structure roadway cement mortar made of rock-like materials, thereby solving the aforementioned technical problem.

[0008] A method for preparing a physical model of a layered structure cement mortar tunnel using a rock-like material, specifically including the following steps:

[0009] S1: Molds are made according to the site conditions and expected dimensions. The molds include the unit plates required for construction. Pre-cut tunnel holes are drilled in the unit plates, and then the unit plates are assembled.

[0010] S2: Make a tunnel model. After the mold is assembled, insert it through the pre-set tunnel hole in the opposite direction to make the assembled mold.

[0011] S3: Place the combined mold on the retractable support device;

[0012] S4: Apply release agent to the inner wall of the mold and the outside of the tunnel model, pour rock-like material layer by layer, highlighting the existence of layered joints during the pouring process, and scrape the surface smooth after compaction.

[0013] S5: Demolding and curing to obtain a physical model of the layered structure roadway cement mortar.

[0014] in:

[0015] In step S1, the mold consists of five unit plates forming the bottom and side surfaces, with a thickness of 8-10mm. Two of these plates, each with pre-set channel holes, are assembled facing each other. The mold is made of a combination of transparent and opaque materials, or a transparent material. The transparent material is acrylic or glass, while the opaque material is wood, iron, PP plastic, or nylon. When a combination of transparent and opaque materials is used, at least one side is made of transparent material.

[0016] In step S1, a pre-set tunnel hole is drilled at the center of the unit plate. The pre-set tunnel hole is a straight-walled semi-circular arch, 50-70mm wide and 70-90mm high.

[0017] In step S2, the material of the tunnel model is selected from wood, solid glass, foam, and PP plastic, and its size is the same as the preset tunnel hole.

[0018] In step S3, the telescopic support device consists of a square steel base, a rotatable platform, and four hydraulic support telescopic rods. The rotatable platform is located at the center of the steel base, and the four hydraulic support telescopic rods are located at the four corners of the steel base.

[0019] In step S4, the release agent is dimethyl silicone oil with a viscosity of 800-1000 cs, and the rock-like material is specifically cement mortar with mechanical properties similar to the simulated layered rock mass. The thickness of each layer of rock-like material is determined according to the on-site engineering conditions or research objectives.

[0020] The mass ratio of cement, river sand, and water in the cement mortar is (1-1.5):(4.5-5.5):(1-1.3), wherein the cement used is 325 or 425 cement, and the particle size of the river sand is 40-70 mesh.

[0021] In step S4, when casting the physical model with an inclination angle, the height of the hydraulic support telescopic rod is raised or lowered.

[0022] In step S4, highlighting the layered joints specifically involves: after each layer of cement mortar has been initially set for 1 to 2 hours, laying mica flakes or mica powder with a particle size of 0.5 to 2.3 mm, and then pouring the next layer.

[0023] In step S5, the tunnel model is extracted from the mold before demolding; the curing conditions are constant temperature and humidity, with a curing temperature of 22±2℃, a relative humidity of 90%~95%, and a curing time of 14~28 days, after which the sample is polished.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The mold of the present invention uses transparent material on one or more sides, which makes the material easy to observe during the casting process so as to make timely adjustments to the model.

[0026] 2. The present invention pre-sets tunnel holes on the mold, ensuring the similarity between the final physical model and the tunnel of the layered rock mass of the deep metal mine.

[0027] 3. The cement grade of this invention can be selected as 325 or 425, and the number of layers can be poured according to the actual project.

[0028] 4. The combined mold produced by this invention can be rotated at different angles by a telescopic support device, thereby producing layered rock mass models at different inclination angles.

[0029] 5. This invention uses cement mortar, formed by mixing ordinary cement, river sand and water, to prepare a physical model. The resulting model is similar to a layered rock tunnel, which reduces the difficulty and cost of obtaining layered rock masses.

[0030] 6. The physical model obtained by the present invention can ensure its integrity and strength while facilitating demolding. Attached Figure Description

[0031] Figure 1 A process flow diagram of a method for preparing a physical model of a layered rock-like material tunnel cement mortar according to the present invention;

[0032] Figure 2 A schematic diagram of the physical model of the layered structure of rock-like material roadway cement mortar prepared in Example 1 of the present invention; wherein θ is the bedding dip angle;

[0033] Figure 3 The front view of the combined mold of the physical model of the layered structure of rock-like material roadway cement mortar prepared in Embodiment 1 of the present invention placed on a telescopic support device; wherein: 1-combined mold, 2-transparent acrylic plate, 3-preset roadway hole, 4-rotatable table, 5-hydraulic support telescopic rod, 6-steel base.

[0034] Figure 4 The combined mold of the rock-like layered structure roadway cement mortar physical model prepared in Embodiment 1 of the present invention is placed on a telescopic support device, and the structural schematic front view is shown when tilted at θ°.

[0035] Figure 5 The combined mold of the rock-like layered structure roadway cement mortar physical model prepared in Embodiment 1 of the present invention is placed on a telescopic support device, and the structural schematic side view is shown when tilted at θ°. Detailed Implementation

[0036] The preferred embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for illustrating and explaining the present invention and should not be used to limit the scope of protection of the present invention.

[0037] Example 1

[0038] A method for preparing a physical model of a layered structure cement mortar for roadways using rock-like materials, the process flow diagram of which is shown below. Figure 1 As shown, the physical model of the layered structure cement mortar tunnel of the rock-like material is as follows: Figure 2 As shown, the specific steps include:

[0039] S1: The mold is made according to the site conditions and expected dimensions. The mold is made of five unit panels spliced ​​together to form the bottom and sides. The unit panels are 10mm thick transparent acrylic panels 2. Two of the panels with pre-set tunnel holes are assembled opposite each other. Pre-cut straight wall semi-circular arched tunnel holes with a width of 70mm and a height of 90mm are drilled in advance on the front and back unit panels that are assembled opposite each other. Then the unit panels are assembled.

[0040] S2: Make a wooden tunnel model with the same size as the pre-excavated tunnel hole 3. After the mold is assembled, insert it through the pre-excavated tunnel hole 3 to make the combined mold 1. The wooden tunnel model is used to simulate a tunnel in a layered surrounding rock.

[0041] S3: Place the combined mold 1 on the telescopic support device. The transparent acrylic sheet 2 allows for easy observation of the physical model's fabrication process while ensuring strength. The telescopic support device consists of a square steel base 6, a rotatable platform 4, and four hydraulic support telescopic rods 5. The rotatable platform 4 is located at the center of the steel base 6, and the four hydraulic support telescopic rods 5 are located at the four corners of the steel base 6, in pairs on opposite sides. The hydraulic support telescopic rods 5 can be raised or lowered by rotating relative to the opposite side to form the desired tilt angle.

[0042] S4: Apply 1000cs viscosity dimethyl silicone oil to the inner wall of the mold and the outer surface of the tunnel model, then pour rock-like material layer by layer. The rock-like material is specifically cement mortar with mechanical properties similar to the simulated layered rock mass. The mass ratio of cement, river sand, and water in the cement mortar is 1:4.9:1.1, using 325 cement and 70-mesh river sand. The thickness of each layer of rock-like material is determined based on site conditions or research objectives. During pouring, after each layer of cement mortar has initially set for 2 hours, lay 2mm mica flakes or powder before pouring the next layer. If pouring a physical model with an angle is required, this is done by raising or lowering the height of the hydraulic support telescopic rods, compacting the surface, and then leveling it.

[0043] S5: Under curing conditions of 22±2℃ and 90%~95% relative humidity, the tunnel model was demolded and cured for 28 days. Before demolding, the tunnel model was removed from the mold, and the sample was then polished to obtain a physical model of the layered tunnel cement mortar. The front view of the combined mold 1 of the prepared rock-like layered tunnel cement mortar physical model placed on the retractable support device is shown below. Figure 3 As shown, the schematic front view of the combined mold 1 when tilted at θ° is as follows. Figure 4 As shown, the schematic side view of the combined mold 1 when tilted at θ° is as follows. Figure 5 As shown.

[0044] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can still make improvements to the technical solutions of the foregoing embodiments. Any modifications, equivalent substitutions, or improvements made without departing from the technical principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a layered structure of a rock-like material of a roadway cement mortar physical model, characterized by, Specifically comprising the following steps: S1: According to the engineering site conditions and the predicted size, a mold is made, which is composed of five unit plates for the bottom and side surfaces, with a thickness of 8-10 mm, wherein two plates with preset roadway holes are oppositely assembled, the preset roadway holes are straight wall semi-circular arch type, with a width of 50-70 mm and a height of 70-90 mm, and then the unit plates are combined; the material of the mold is a combination of transparent material and opaque material, or transparent material, wherein the transparent material is acrylic plate or glass, and the opaque material is wood plate, iron plate, PP plastic plate or nylon plate, when the combination of transparent material and opaque material is selected, at least one side is selected to be transparent material; S2: After the mold combination is completed, a roadway model is inserted along the opposite preset roadway holes to obtain a combined mold; S3: The combined mold is placed on a telescopic support device, which is composed of a square steel base, a rotatable table and four hydraulic support telescopic rods, the rotatable table is arranged at the center of the steel base, and the four hydraulic support telescopic rods are arranged at the four corners of the steel base, the hydraulic support telescopic rods can be lifted or lowered in height and rotated relative to the other side to form the required inclination angle; S4: A release agent is applied to the inner wall of the mold and the outside of the roadway model, and a layered rock-like material is poured layer by layer, the existence of layered joints is highlighted during pouring, and the surface is scraped flat after vibration and compaction; wherein the layered rock-like material is specifically cement mortar similar in mechanical properties to the simulated layered rock mass, the mass ratio of cement, river sand and water in the cement mortar is (1-1.5):(4.5-5.5):(1-1.3), cement 325 or 425 is used, and the particle size of river sand is 40-70 mesh; the highlighted layered joints are specifically: after each layer of cement mortar has been initially cured for 1-2 hours, mica sheets or mica powder with a particle size of 0.5-2.3 mm are laid, and then the pouring of the next layer is performed; when pouring the physical model with an inclination angle, the height of the hydraulic support telescopic rod is lifted or lowered to complete the pouring; S5: Demolding and curing, the roadway model is removed from the model before demolding to obtain a layered structure roadway cement mortar physical model.

2. A method of preparing a layered rock-like material physical model of a roadway cement mortar according to claim 1, characterized in that, In step S2, the material of the roadway model is selected from one of wood, solid glass, foam and PP plastic, and the size is the same as that of the preset roadway hole.

3. A method of preparing a layered rock-like material physical model of a roadway cement mortar according to claim 1, characterized in that, In step S4, the release agent is dimethyl silicone oil with a viscosity of 800-1000 cs.

4. A method of preparing a layered rock-like material physical model of a roadway cement mortar according to claim 1, characterized in that, In step S5, the curing conditions are constant temperature and humidity, wherein the curing temperature is 22±2℃, the relative humidity is 90%-95%, the curing time is 14-28 days, and then the sample is polished.

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