A geotechnical inclinometer based on flexible distributed sensors and method

Abstract

The application discloses a kind of rock-soil body inclinometer device and method based on flexible distributed sensor, it is related to rock-soil engineering monitoring technical field, including multiple sections and sequentially spliced guide rod, terminal guide rod installs guide head;Along the inner wall of guide rod axial setting guide groove, the junction end of guide head and guide rod is equipped with clamping groove, the guide groove is used to guide flexible distributed sensor into guide rod, and makes the end of flexible distributed sensor and the clamping groove plug-in;Wherein, the flexible distributed sensor has double-layer conductive layer, to obtain the bending deformation state of rock-soil body based on the resistance difference of double-layer conductive layer.The application can make flexible distributed sensor enter borehole with vertical state by guiding device, and make flexible distributed sensor can be continuously monitored in borehole by rapid-setting cement, improve inclining precision.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering monitoring technology, and in particular to a geotechnical inclination measurement device and method based on flexible distributed sensors. Background Technology

[0002] Geotechnical stability monitoring is a crucial step in ensuring the safety of infrastructure such as slopes, foundation pits, tunnels, and dams. Deep horizontal displacement (inclinometer) monitoring, as a core technology for assessing soil or structural deformation trends, primarily relies on rigid inclinometers or fixed tilt sensor arrays. Traditional methods, which extrapolate overall deformation through segmented measurements or discrete point data, suffer from the following drawbacks: rigid sensors struggle to adapt to non-uniform deformation within complex geological structures, easily leading to measurement failures or even damage due to localized stress concentrations; discrete point measurement modes struggle to capture continuous deformation fields with high spatial resolution, risking the omission of critical slip surface information; mobile inclinometers rely on manual operation, preventing real-time continuous monitoring; and fixed sensors involve complex installation processes, difficult maintenance, and significant measurement errors can be introduced by factors such as wear and misalignment of the inclinometer guide wheels. While fiber optic sensors have become a widely used geotechnical inclinometer technology in recent years, they suffer from susceptibility to environmental interference, insufficient long-term stability, and high monitoring costs.

[0003] The development of flexible electronics and distributed sensing technology has provided new ideas for geotechnical monitoring. Flexible sensors can be closely attached to the monitoring surface or embedded inside the soil or rock mass to achieve fully distributed strain field sensing. However, the current applications of flexible sensors in geotechnical engineering are mostly concentrated on surface stress and strain monitoring, and are mostly discrete point monitoring. Due to the lack of dedicated supporting devices for long-term reliable installation inside the soil or rock mass, flexible sensors are difficult to use for distributed continuous monitoring of horizontal displacement of the soil or rock mass. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a rock and soil inclination measurement device and method based on a flexible distributed sensor. The device guides the flexible distributed sensor to enter the borehole vertically, and the quick-setting cement enables the flexible distributed sensor to continuously monitor inside the borehole, thereby improving the inclination measurement accuracy.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a rock and soil inclinometer based on a flexible distributed sensor, comprising multiple guide rods spliced ​​together in sequence, with a guide head installed at the end of the guide rod; a guide groove is provided along the axial direction of the inner wall of the guide rod, and a slot is provided at the connection end of the guide head and the guide rod, the guide groove being used to guide the flexible distributed sensor into the guide rod and to allow the end of the flexible distributed sensor to be inserted into the slot;

[0007] The flexible distributed sensor has a double conductive layer to obtain the deformation state of the soil and rock mass based on the resistance difference between the two conductive layers.

[0008] As a further implementation, the guide groove is symmetrically arranged with respect to the central axis of the guide rod, and the slot is coplanar with the guide groove.

[0009] As a further implementation, the flexible distributed sensor is connected to a fixing card at its end, and the fixing card is inserted into a card slot.

[0010] As a further implementation, multiple barbed cones are distributed around the guide head.

[0011] As a further implementation, a multi-channel resistance acquisition device is also included, which is used to receive measurement data from the flexible distributed sensor and convert the resistance data into displacement data.

[0012] Secondly, embodiments of the present invention also provide a method for inclinometer measurement of soil and rock masses based on a flexible distributed sensor, employing the aforementioned inclinometer device, comprising:

[0013] Lower the guide rod to the bottom of the hole, inject quick-setting cement grout into the guide rod, and cure for the set time;

[0014] Remove each guide rod in sequence. For each guide rod length that is lifted, fill the hole with backfill material and compact it in layers.

[0015] Connect the flexible distributed sensor to the multi-channel resistance acquisition instrument, let it stand for a set time, and then acquire the initial resistance value; then acquire multiple resistance values ​​according to the set sampling frequency.

[0016] Based on the resistance difference between the two conductive layers, a functional relationship between the resistance difference and the bending angle and radius of curvature is established to obtain inclination measurement data.

[0017] As a further implementation method, the verticality is calibrated in real time using a laser plumb line during the lowering of the guide rod, and a set amount of quick-setting cement is injected to fix the guide head.

[0018] As a further implementation, the backfill material is a bentonite-sand mixture;

[0019] Backfill with epoxy resin mortar within the set range of the orifice.

[0020] As a further implementation, the functional relationship between the resistance difference and the bending angle and radius of curvature is expressed as follows:

[0021]

[0022] Where R0 represents the initial resistance value, Indicates the radius of curvature. Indicates the bending angle. This represents the change in resistance of the first conductive layer in a flexible distributed sensor. This represents the resistance change of the second conductive layer in the flexible distributed sensor. This represents the initial length between two adjacent electrodes. Indicates the sensitivity of the conductive layer. This represents the distance between the conductive layer and the neutral axis. Indicates the thickness of the conductive layer. This represents the amount of soil deformation between the m-th electrode segment. This represents the chord length corresponding to the central angle of the m-th bending segment.

[0023] As a further implementation, the sampling frequency is adjusted according to weather conditions, wherein the sampling time interval in sunny mode is longer than the sampling time interval in rainy mode.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The guide rod of the present invention is provided with a guide groove and the guide head is provided with a slot. The flexible distributed sensor cooperates with the slot under the guidance of the guide groove, which can keep the flexible distributed sensor in a vertical state and prevent large deformation or bending, thus ensuring measurement accuracy. The flexible distributed sensor has a double conductive layer. The deformation state of the rock and soil is obtained through the resistance difference of the double conductive layer, thus obtaining accurate inclination data.

[0026] (2) The flexible distributed sensor of the present invention has a double conductive layer. By measuring the resistance difference between the two conductive layers and establishing the functional relationship between the resistance difference and the bending angle and radius of curvature, the inclination data can be obtained, which can eliminate the influence of temperature drift and settlement deformation.

[0027] (3) The guide head anchoring of the present invention uses quick-setting cement to fill the gap between the guide head and the borehole, and the guide head is left at the bottom of the hole as the anchoring end; after the quick-setting cement has solidified, the guide rod is removed and the backfilling is carried out. During the backfilling process, the layer compaction is ensured to be tightly attached to the hole wall, so as to ensure that the flexible distributed sensor is synchronized with the soil deformation and improve the inclination measurement accuracy. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 This is a schematic diagram of the inclinometer device according to one or more embodiments of the present invention;

[0030] Figure 2(a) is a perspective view of the guide rod according to one or more embodiments of the present invention;

[0031] Figure 2(b) is a top view of the guide rod according to one or more embodiments of the present invention;

[0032] Figure 3 This is a perspective view of the guide head according to one or more embodiments of the present invention;

[0033] Figure 4(a) is a schematic diagram of the connecting plate structure according to one or more embodiments of the present invention;

[0034] Figure 4(b) is a side view of the connecting plate installation according to one or more embodiments of the present invention;

[0035] Figure 4(c) is a top view of the connection plate installation according to one or more embodiments of the present invention;

[0036] Figure 5 This is a schematic diagram of the connection between the flexible distributed sensor and the fixed card according to one or more embodiments of the present invention;

[0037] Figure 6(a) is a front view of the flexible distributed sensor according to one or more embodiments of the present invention;

[0038] Figure 6(b) is a top view of the flexible distributed sensor according to one or more embodiments of the present invention;

[0039] Figure 7 This is a schematic diagram of roadbed slope monitoring according to one or more embodiments of the present invention;

[0040] Figure 8 This is a schematic diagram of the deformation monitoring of the superstructure caused by tunnel excavation according to one or more embodiments of the present invention;

[0041] Figure 9 This is a schematic diagram of horizontal deformation monitoring during deep foundation pit excavation according to one or more embodiments of the present invention.

[0042] Among them, 1. guide rod, 2. guide head, 3. flexible distributed sensor, 31. substrate, 32. encapsulation layer, 33. conductive layer, 34. electrode, 35. wire; 4. guide groove, 5. slot, 6. barbed cone, 7. connecting plate, 8. bolt, 9. drill hole, 10. fixing clip, 11. backfill material, 12. wire, 13. building, 14. tunnel. Detailed Implementation

[0043] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0044] Example 1:

[0045] This embodiment provides a rock and soil inclinometer based on a flexible distributed sensor, such as... Figure 1 As shown, it mainly includes a guide rod 1, a guide head 2, a flexible distributed sensor 3, and a multi-channel resistance acquisition instrument. The guide rod 1 serves as the mounting carrier for the flexible distributed sensor 3, which is used to send the flexible distributed sensor 3 into the borehole 9. The flexible distributed sensor 3 has a double conductive layer. By measuring the resistance difference between the two conductive layers, a functional relationship between the sensor and bending deformation is established, thereby obtaining the inclination data of the soil and rock mass.

[0046] In this embodiment, as shown in FIG6(a), the flexible distributed sensor 3 is a sheet-like structure with a certain length, consisting of a double conductive layer 33, namely a first conductive layer and a second conductive layer, with a substrate 31 between the first and second conductive layers, and an encapsulation layer 32 disposed on the outside of the conductive layer 33. As shown in FIG6(b), the conductive layer 33 is led out by multiple electrodes 34 and connected to wires 35 to realize distributed measurement.

[0047] In this embodiment, the substrate 31 has a thickness of 1.5~2.0mm, the conductive layer 33 has a thickness of 0.3~0.4mm, the electrode 34 has a thickness of 0.3~0.5mm, the encapsulation layer 32 has a thickness of 1.0~1.3mm, and the flexible distributed sensor 3 has a width of 4.0~6.0mm.

[0048] Because the flexible distributed sensor 3 is flexible, a guide rod 1 is provided in this embodiment to smoothly insert the flexible distributed sensor 3 into the borehole 9 without deforming it. The guide rod 1 has multiple sections to deliver the flexible distributed sensor 3 into the borehole 9; the specific number of sections of the guide rod 1 is determined according to the depth of the borehole 9.

[0049] like Figure 1 As shown, multiple guide rods 1 are sequentially spliced ​​together, and a guide head 2 is installed at the bottom of the last guide rod 1. The multiple guide rods 1 and the guide head 2 constitute a guiding device. After the flexible distributed sensor 3 is sent into the borehole 9, backfill material 11 is filled. The guide head 2 and the flexible distributed sensor 3 remain in the borehole 9, and the guide rods 1 need to be removed. To facilitate quick separation and disassembly of the guide rods 1, the guide head 2 and the guide rod 1 are magnetically connected, and adjacent guide rods 1 are connected by a connecting structure.

[0050] In this embodiment, the length of each guide rod 1 is 1.5~2.0m, the outer diameter of the guide rod 1 is 60mm, and the inner diameter is 50mm; of course, in other embodiments, the above parameters can be adjusted according to actual requirements.

[0051] As shown in Figures 2(a) and 2(b), the inner wall of the guide rod 1 is provided with guide grooves 4. The guide grooves 4 are arranged along the axial direction of the guide rod 1, and the guide grooves 4 are symmetrically arranged with respect to the central axis of the guide rod 1, that is, two guide grooves 4 are provided in total. The flexible distributed sensor 3 is inserted into the guide rod 1 through the two opposing guide grooves 4. At the same time, the guide grooves 4 can also restrict the lateral displacement of the flexible distributed sensor 3, so that the flexible distributed sensor 3 is kept in a vertical state in the guide rod 1, avoiding bending or twisting of the flexible distributed sensor 3 and ensuring measurement accuracy.

[0052] The guide groove 4 consists of two protrusions with a certain distance between them. The length of the protrusions is equal to or slightly less than the length of the guide rod 1, and the height of the protrusions is 3~4mm, so as to provide good limiting for the flexible distributed sensor 3. The inner wall of the guide groove 4 is coated with a polytetrafluoroethylene wear-resistant layer to reduce friction and allow the flexible distributed sensor 3 to enter the guide groove 4 smoothly.

[0053] like Figure 3 As shown, the guide head 2 has a conical structure with multiple barbed cones 6 evenly distributed around its periphery, which enhances the anchoring force with the bottom of the hole. In this embodiment, the tip angle of the guide head 2 is 30°~45°. Both the guide head 2 and the guide rod 1 are made of metal (e.g., stainless steel), so a magnetic attraction structure is provided between them to achieve quick assembly and disassembly of the guide head 2 and the guide rod 1.

[0054] The end face of the guide head 2 and the guide rod 1 is provided with a slot 5. The slot 5 is arranged radially along the guide head 2 and is coplanar with the guide groove 4, so that the flexible distributed sensor 3 can be introduced into the slot 5 after passing through the guide groove 4. In order to ensure that the flexible distributed sensor 3 can be accurately engaged with the slot 5 and to avoid the flexible distributed sensor 3 not being able to be accurately engaged into the slot 5 due to its flexibility, such as... Figure 5 As shown, a fixing clip 10 is connected to the end of the flexible distributed sensor 3. The fixing clip 10 is made of metal or other rigid material and can form a good fit with the slot 5. A spring clip is provided in the slot 5 to achieve quick and effective connection with the fixing clip 10.

[0055] Since the guide rod 1 is a cylindrical structure, the connection structure of this embodiment includes several arc-shaped connecting plates 7, as shown in Figures 4(a)-4(c). The connecting plates 7 are attached to the side wall of the connecting position of the guide rod 1, and the connecting plates 7 and the guide rod 1 are fixed by bolts 8.

[0056] The top of the flexible distributed sensor 3 is connected to the multi-channel resistance acquisition instrument via a lead wire 12. The multi-channel resistance acquisition instrument is connected to the controller via a wireless transmission module. The controller has a built-in edge computing unit that can execute the resistance-displacement conversion algorithm in real time and obtain displacement data from the resistance data.

[0057] In this embodiment, quick-setting cement is used to fill the gap between the flexible distributed sensor 3 and the borehole 9, and the guide head 2 is left at the bottom of the hole as the anchor end. After the quick-setting cement has solidified, the guide rod 1 is removed while the backfill material 11 is filled. During the backfilling process, it is ensured that the material is compacted in layers to fit closely to the hole wall, so as to ensure that the flexible distributed sensor 3 deforms synchronously with the soil.

[0058] Example 2:

[0059] This embodiment provides a method for inclinometer measurement of soil and rock masses based on flexible distributed sensors, such as... Figure 7 As shown, multiple monitoring holes are arranged in a grid pattern on the slope. The inclinometer device described in Example 1 is used to monitor the location of the potential sliding surface, including the following steps:

[0060] Step 1: Drilling and sensor installation.

[0061] A reverse circulation drilling rig was used to form the hole. The diameter of the hole 9 was 90mm. The stability of the hole wall was tested every 2m. The flexible distributed sensor 3 was embedded in the guide groove 4 of the guide rod 1 to ensure that the flexible distributed sensor 3 was in close contact with the inner wall of the guide groove 4 (gap < 0.1mm). The guide rod 1 was installed section by section to ensure that the flexible distributed sensor 3 was placed in the guide groove 4 of the guide rod 1. After the hole 9 was completed, the verticality was calibrated with a laser inclinometer (the deviation was corrected to within 0.5°).

[0062] Step 2: Lower and anchor guide rod 1.

[0063] Connect the guide head 2 magnetically to the end guide rod 1, and lower the connected guide device to the bottom of the hole. During the lowering process, calibrate the verticality in real time using a laser plumb line (deviation ≤ 0.5°), and inject a certain amount of quick-setting cement to fix the guide head 2; the amount of quick-setting cement injected meets the fixing requirements of the guide head 2. After the guide head 2 is lowered to the bottom of the hole, inject quick-setting cement grout (grouting pressure 0.5MPa) through the internal channel of the guide rod 1, and cure for 6 hours until the strength meets the standard.

[0064] It should be noted that the quick-setting cement is injected into the guide rod 1 at a certain speed. This speed is required not to cause excessive impact on the flexible distributed sensor 3, so as to avoid bending and deformation of the flexible distributed sensor 3.

[0065] Step 3: Remove guide rod 1 and couple it with the filling.

[0066] After the quick-setting cement has cured, the guide rod 1 is lifted and backfill material 11 is filled. The guide rod 1 is lifted section by section and backfilled. For soil environments, a bentonite-sand mixture (mass ratio 1:3) is used as the backfill material 11; for rock environments, cement slurry with a water-cement ratio of 0.8:1 is used, with 0.5%~1% expansion agent added. The grouting pressure is 0.2~0.5MPa. A micro-vibrator is used for layered compaction (each layer 0.3~0.8m thick). Epoxy resin mortar is backfilled within 3m of the borehole opening to prevent rainwater erosion.

[0067] Step 4: Signal connection and data acquisition.

[0068] Lead the sensor wire 12 out to the orifice protection box and connect it to the multi-channel synchronous acquisition instrument. After installation, let it stand for 72 hours and collect the initial resistance value. Set the adaptive sampling frequency. In this embodiment, the sampling frequency is 1 time / 2 hours in sunny mode and 1 time / 5 minutes in rainy mode.

[0069] Step 5: By collecting and analyzing the resistance difference between the two conductive layers 33, a functional relationship between the resistance difference and the bending angle and radius of curvature is established, thereby realizing the inclination measurement work in geotechnical engineering. The specific calculation formula is as follows:

[0070]

[0071] In the above formula, R0 represents the initial resistance value. Indicates the radius of curvature. Indicates the bending angle. This represents the change in resistance of the first conductive layer of the flexible distributed sensor 3. This represents the change in resistance of the second conductive layer of the flexible distributed sensor 3. This represents the initial length between two adjacent electrodes 34. This indicates the sensitivity of conductive layer 33. This indicates the distance between the conductive layer 33 and the neutral axis. This indicates the thickness of the conductive layer 33. This represents the amount of soil deformation between electrodes 34 in the m-th segment. This represents the chord length corresponding to the central angle of the m-th bending segment.

[0072] In this embodiment, during construction, the first segment is defined as the area between the bottommost electrode 34 and the adjacent electrode 34 on the upper side, arranged from bottom to top.

[0073] The relationship between the change in resistance and the amount of deformation during soil settlement and deformation is shown in Table 1.

[0074] This embodiment uses a dual-layer resistance differential algorithm to eliminate the effects of temperature drift and settlement deformation.

[0075] Step 6: Connect to the remote monitoring platform. The remote monitoring platform can display the displacement-time curve in real time and has a threshold alarm function.

[0076] Table 1 Relationship between soil resistivity change and deformation amount during soil settlement and deformation

[0077]

[0078] Example 3:

[0079] This embodiment provides a method for inclinometer measurement of soil and rock masses based on flexible distributed sensors, such as... Figure 8 As shown, this method is applied to monitor the horizontal deformation of the superstructure 13 during the construction of tunnel 14. A monitoring network is set up in the foundation of the structure and the surrounding soil. At least three boreholes are set up according to the size of the structure 13. The specific monitoring process is the same as in Example 2, and will not be repeated here.

[0080] Example 4:

[0081] This embodiment provides a method for inclinometer measurement of soil and rock masses based on flexible distributed sensors, applied to real-time monitoring of horizontal deformation during deep foundation pit excavation, such as... Figure 9 As shown, based on the excavation depth of the foundation pit project design, the geological survey report revealing the stratum distribution characteristics (especially the location of potential sliding surfaces and weak interlayers), and relevant specifications, the drilling depth of monitoring borehole 9 is comprehensively determined. Based on the scale, shape, excavation depth, support structure type, surrounding environmental sensitivity, and geological conditions of the foundation pit, monitoring boreholes are reasonably arranged along the perimeter of the foundation pit, focusing on high-risk areas. The spacing between boreholes needs to take into account the effective measurement range of the sensors and the expected deformation gradient.

[0082] The sensor installation and backfilling were carried out according to the steps in Example 2. The signal cable from the sensor was led to the ground data acquisition box, and the acquisition frequency was set to 1 time / 1h. The specific calculation method for horizontal displacement was the same as in Example 2.

[0083] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A flexible distributed sensor based inclinometry method for rock mass, characterized in that, The inclinometer device comprises a plurality of guide rods connected in sequence, and a guide head is installed at the end of the guide rods; a guide groove is arranged axially along the inner wall of the guide rod, a clamping groove is arranged at the joint end of the guide head and the guide rod, and the guide groove is used to guide the flexible distributed sensor into the guide rod and make the end of the flexible distributed sensor inserted into the clamping groove; The flexible distributed sensor has a double-layer conductive layer, and the deformation state of the rock-soil body is obtained based on the resistance difference of the double-layer conductive layer; The inclinometer method comprises the following steps: The guide rod is lowered to the bottom of the hole, the quick-setting cement slurry is injected into the guide rod, and the setting time is maintained; Each guide rod is taken out in sequence, wherein the backfill material is filled into the hole and compacted layer by layer every time the guide rod is lifted by a length; The wires of the flexible distributed sensor are connected to the multi-channel resistance acquisition instrument, and the initial resistance value is collected after being placed for a set time; then a plurality of resistance values are collected according to the set sampling frequency; The function relationship between the resistance difference of the two-layer conductive layer and the bending angle and the radius of curvature is established to obtain the inclinometer data. The function relationship between the resistance difference and the bending angle and the radius of curvature is expressed as: wherein R0 represents an initial resistance value, represents a radius of curvature, represents a bending angle, represents a first conductive layer resistance change of the flexible distributed sensor, represents a second conductive layer resistance change of the flexible distributed sensor, represents an initial length between two adjacent electrodes, represents a sensitivity of the conductive layer, represents a distance between the conductive layer and the neutral axis, represents a thickness of the conductive layer, represents a soil deformation amount between the mth segment electrodes, represents a chord length corresponding to the central angle of the mth segment bending angle.

2. The method according to claim 1, wherein, The guide groove is symmetrically arranged relative to the central axis of the guide rod, and the clamping groove is coplanarly arranged with the guide groove.

3. The method according to claim 1 or 2, wherein, The end of the flexible distributed sensor is connected to a fixed clasp, and the fixed clasp is inserted into the clamping groove.

4. The method according to claim 1, wherein, A plurality of barbed cones are distributed around the guide head.

5. The method of claim 1, wherein, The multi-channel resistance acquisition instrument is also included, which is used to receive the measurement data of the flexible distributed sensor and convert the resistance data into displacement data.

6. The method of claim 1, wherein, The verticality is calibrated in real time by a laser plummet during the lowering of the guide rod, and a certain amount of quick-setting cement is injected to fix the guide head.

7. The method of claim 1, wherein, The backfill material is a bentonite-sand mixture; Epoxy resin mortar is backfilled within a certain range of the hole opening.

8. The method of claim 1, wherein, The sampling frequency is adjusted according to the weather conditions, wherein the sampling time interval in sunny mode is greater than that in rainy mode.

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