A monitoring device and method for underground water level during construction

Abstract

The present invention discloses a monitoring device for the groundwater level during construction, comprising: two parallel and spaced measuring lines, each measuring line including a wire core, and the two wire cores being parallel to each other; a resistance wire is helically wound along the length direction on each wire core, and each resistance wire is closely attached to the corresponding wire core, and the ends of the two resistance wires are both used for connecting wires; a wire casing is coaxially sleeved outside each measuring line, and each wire casing is a cylindrical body with both ends closed. A conductive gap casing is integrally connected between the two wire casings, and the length of the conductive gap casing is the same as the length of each wire casing; the inner cavity of the conductive gap casing is a conductive gap, and the conductive gap is communicated with the inner cavities of the two wire casings. A plurality of water inlet holes are spaced along the length direction on the conductive gap casing, for allowing the water in the formation to flow into the conductive gap and be introduced into the inner cavities of the two wire casings through the conductive gap. So as to reduce the cost and difficulty of measuring point layout and measuring point maintenance, and simplify the daily measurement work.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground engineering monitoring and measurement, and in particular relates to a monitoring device and method for underground water level during the construction process.

Background Art

[0002] In underground engineering, the existence of groundwater is one of the most important factors affecting engineering safety, progress and quality. Therefore, during the whole process of construction, it is necessary to closely monitor the occurrence state of groundwater in order to timely adjust construction measures, scientifically and reasonably respond to groundwater, and avoid safety accidents and project delays. The most widely used monitoring target is the underground water level. Through a ground borehole, a PVC pipe is inserted, and then measured with a tape water level gauge. When measuring, a probe is put into the PVC pipe. After the probe touches the water surface in the pipe, it makes a sound, and the length of the tape is recorded, which is the buried depth of the underground water level.

[0003] This method is intuitive and easy to understand, but there are deficiencies in the actual construction process: First, it is not easy to arrange measuring points, which requires drilling and pipe insertion, and the comprehensive cost is relatively high; Second, after the measuring points are arranged, with the progress of the project construction, the equipment, materials and muck are frequently transported, and it is very easy to damage or block the measuring points, and the maintenance work is relatively heavy; Third, the measurement is slow and inconvenient. The surveyor needs to hold a relatively heavy tape water level gauge, gradually lower the probe until it reaches the water surface, and then gradually retract it after reading.

[0004] Therefore, during the construction process of underground engineering, a faster and more convenient method for measuring the underground water level is needed to reduce the cost and difficulty of measuring point arrangement and measuring point maintenance, and at the same time perform the measurement work faster and more conveniently.

Summary of the Invention

[0005] The purpose of the present invention is to provide a monitoring method for underground water level during the construction process to reduce the cost and difficulty of measuring point arrangement and measuring point maintenance and simplify the daily measurement work.

[0006] The present invention adopts the following technical solutions: A monitoring device for underground water level during the construction process is used for being vertically buried in the soil body to monitor the change of the water level in the stratum; it includes:

[0007] Two parallel and spaced measuring lines, each measuring line includes a wire core, the two wire cores are parallel to each other and are both made of non-conductive materials;

[0008] A resistance wire is spirally wound along the length direction on each wire core, each resistance wire is closely attached to the corresponding wire core, and the ends of the two resistance wires are both used for connecting wires; A wire shell is coaxially sleeved outside each measuring line, and each wire shell is a closed circular cylinder at both ends.

[0009] A conductive gap housing is integrally connected between two wire housings, and the length of the conductive gap housing is the same as that of each wire housing; the inner cavity of the conductive gap housing is a conductive gap, and the conductive gap is connected to the inner cavities of the two wire housings. On the conductive gap housing, a plurality of water inlet holes are spaced along its length direction for allowing water in the formation to flow into the conductive gap and be introduced into the inner cavities of the two wire housings through the conductive gap.

[0010] Further, the conductive gap housing is in the shape of a cuboid, and its length is consistent with the lengths of the two wire housings.

[0011] Further, the width of the conductive gap housing is less than 5 mm.

[0012] Further, on each wire core, the spacing of the resistance wire winding is equal.

[0013] Further, the two resistance wires are made of the same material, have the same length, and the same winding method.

[0014] The present invention also discloses a method for monitoring the underground water level during construction, using the above-mentioned device for monitoring the underground water level during construction. The method is as follows:

[0015] Step 1: Vertically bury the monitoring device in the soil mass.

[0016] Step 2: Take the initial value: Connect the wires at the ends of the two resistance wires to the two probes of the ohmmeter respectively. The initial resistance value measured by the ohmmeter is R1; calculate the initial underground water level depth as: h1 = R1 / 2ab; remove the ohmmeter.

[0017] Step 3: Monitor again: During the construction process, when monitoring again according to the construction monitoring frequency, connect the wires at the ends of the two resistance wires to the two probes of the ohmmeter respectively. The resistance value R2 is measured by the ohmmeter at this time; remove the ohmmeter; calculate the underground water level depth at this time as: h2 = R2 / 2ab.

[0018] Wherein: a is the resistance value per unit length of the resistance wire;

[0019] b is the ratio of the length of the resistance wire 1 to the length of the wire core,

[0020] L is the length of one turn of the resistance wire winding, S is the winding spacing, and d is the wire core diameter.

[0021] It further includes:

[0022] Step 4: Calculate the change value of the underground water level from the underground water level depths in Step 2 and Step 3 as: h2 - h1 = (R2 - R1) / 2ab.

[0023] Further, cotton balls or paper balls are stuffed at the water inlet holes for blocking and filtering sediment.

[0024] Further, in Step 1, the monitoring device is vertically inserted into the soil inclinometer hole or the soil layer settlement hole, tied outside the soil inclinometer tube or the layer settlement tube, and inserted vertically downward into the bottom soil along with the corresponding tube; the length of the buried measuring line is greater than the maximum change depth of the groundwater level.

[0025] The beneficial effects of the present invention are as follows: 1. The measurement is faster and more convenient. Only need to hold an ohmmeter, connect the two measuring lines respectively, and measure the resistance value. Moreover, it outputs in the form of an electrical signal and can be measured immediately after sampling, which is conducive to further realizing automatic measurement. 2. The measuring points are easier to maintain. Only need to protect the exposed measuring lines, without worrying about the damage and blockage of traditional water level tubes. 3. The measuring holes for soil displacement can be utilized and arranged together when measuring the soil depth of the buried layer. The layout of the measuring points is more convenient, saving work efficiency and cost.

Description of the Drawings

[0026] Figure 1 It is a schematic cross-sectional view of a new type of underground water level monitoring wire;

[0027] Figure 2 It is a schematic longitudinal sectional view of a new type of underground water level monitoring wire;

[0028] Figure 3 It is a schematic diagram of the calculation principle for underground water level monitoring;

[0029] Among them: 1 resistance wire, 2 wire core, 3 wire shell, 4 conductive gap, 5 water inlet hole.

Detailed Embodiment

[0030] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0031] A monitoring device for the underground water level during construction of the present invention, as Figure 1 and 2 shown, is used for vertically burying in the soil to monitor the change of the water level in the stratum; it includes: two parallel and spaced measuring lines, each measuring line includes a wire core 2, the two wire cores 2 are parallel to each other and are both made of non-conductive materials.

[0032] A resistance wire 1 is spirally wound along the length direction on each wire core 2, each resistance wire 1 is closely attached to the corresponding wire core 2, and the ends of the two resistance wires 1 are both used for connecting wires. On each wire core 2, the winding spacing of the resistance wire 1 is equal.

[0033] A wire shell 3 is coaxially sleeved outside each of the measuring lines, and each wire shell 3 is a cylindrical body with both ends closed; a conductive gap housing is integrally connected between the two wire shells 3, and the length of the conductive gap housing is the same as the length of each wire shell 3; the inner cavity of the conductive gap housing is a conductive gap 4, and the conductive gap 4 is communicated with the inner cavities of the two wire shells 3.

[0034] On the conductive gap housing, a plurality of water inlet holes 5 are provided at intervals along its length direction, for allowing the water in the formation to flow into the conductive gap 4, and guiding it into the inner cavities of the two wire housings 3 through the conductive gap 4. The conductive gap housing is in the shape of a cuboid, and its length is consistent with the lengths of the two wire housings 3. The width of the conductive gap housing is less than 5 mm.

[0035] The present invention discloses a method for monitoring the groundwater level during construction, using the above-mentioned monitoring device for the groundwater level during construction. The method is as follows:

[0036] Step 1: Vertically bury the monitoring device in the soil body, and the length of the buried measuring wire is greater than the maximum change depth of the groundwater level.

[0037] Step 2: Take the initial value: After the burial is completed, connect the wires at the ends of the two resistance wires 1 to the two measuring needles of the ohmmeter respectively. The initial resistance value measured by the ohmmeter is R1; calculate the initial groundwater level as: h1 = R1 / 2ab; Remove the ohmmeter;

[0038] Step 3: Monitor again: During the construction of the underground project, when monitoring again at the specified monitoring frequency, connect the wires at the ends of the two resistance wires 1 to the two measuring needles of the ohmmeter respectively. The resistance value R2 is measured by the ohmmeter at this time; Remove the ohmmeter; Calculate the groundwater level at this time as: h2 = R2 / 2ab

[0039] Step 4: Calculate the change value of the groundwater level from the groundwater levels in Step 2 and Step 3 as: h2 - h1 = (R2 - R1) / 2ab;

[0040] Where: a is the resistance value per unit length of the resistance wire 1;

[0041] b is the ratio of the length of the resistance wire 1 to the length of the wire core 2;

[0042] L is the length of one turn of the resistance wire 1 wound, S is the winding pitch, and d is the diameter of the wire core 2.

[0043] In Step 1, the monitoring device is vertically inserted into the soil inclinometer hole or the soil layer settlement hole of the soil body, and is tied outside the soil inclinometer tube or the layer settlement tube, and is inserted vertically downward into the bottom soil with the corresponding tube.

[0044] The resistance wire 1 is the core component of the present invention, and the material is nickel-chromium alloy. Considering the three factors of comprehensive cost (the thinner the better), tensile strength (the thicker the better), and resistance (the thinner the better), the cross-sectional area is selected as 1 mm 2The specifications are as follows. Its resistance is about 1Ω / m. The wire core 2 is made of non-conductive polymer material such as plastic, with a diameter of about 5mm. The resistance wire 1 is wound around the wire core 2 to form a measuring wire. When the resistance wire 1 is wound, a constant thread pitch is maintained, so that within the length of the wire core 2 per unit length, the length of the wound resistance wire 1 increases, the measurable resistance value increases, and the measurement accuracy is improved. However, during the winding process of the resistance wire 1, there should be no contact, that is, the thread pitch must be greater than the diameter of the resistance wire 1. After winding, the resistance wire 1 and the wire core 2 are quickly baked at high temperature, so that the surface of the wire core 2 has slight melting, and the resistance wire 1 is preliminarily solidified with it. During subsequent handling and bending processes, the thread pitch of the wound resistance wire 1 will not easily slip and change. The wire shell 3 is made of hard plastic insulation material and is divided into front and rear pieces. After clamping the two measuring wires, it further prevents the relative slippage of the resistance wire 1 and the wire core 2, and the winding thread pitch from changing. The width of the conductive gap 4 is less than 5mm. Equal-spacing water inlet holes 5 with a diameter of 2mm are provided on the longitudinal central axes of the front and rear pieces of the wire shell 3. Groundwater can flow into the conductive gap 4 through it. According to the principle of communicating vessels, after the water flow is balanced, the water level in the conductive gap 4 is the same as the groundwater level. The two sections of the resistance wire 1 above the groundwater level are connected to the groundwater in the conductive gap 4 to form half of an energized circuit. Through the conductivity of water, the resistance wires 1 of the two measuring wires are electrically connected.

[0045] Measurement principle:

[0046] Assume that the resistance value per unit length of the resistance wire 1 is aΩ / m. Through fixed-pitch winding, the length of the resistance wire 1 is b times the length of the wire core 2.

[0047] According to solid geometry knowledge, the calculation formula for the length of a cylindrical thread line is where L is the length of the cylindrical thread line, S is the thread pitch, and d is the diameter of the wire core 2. Then

[0048]

[0049] As Figure 3 shown, after the measuring wire is vertically buried underground, groundwater flows into the conductive gap 4 through the water inlet hole 5. Since water has conductivity, the left and right resistance wires 1 inside the wire shell 3 are connected. Taking the water surface as the boundary, the length of the resistance wire above the groundwater level forms an effective resistance. At this time, on the ground, an ohmmeter is connected to the two resistance wires, and the current resistance R1 can be measured. It is composed of two equal-length resistance wires 1 on the left and right. Since the distance between the two resistance wires 1 is very small, the resistance of the water in the conductive gap 4 can be negligible. So the resistance of each resistance wire 1 is R1 / 2. According to the parameters of the resistance wire, at this time:

[0050] The total length of the resistance wire 1 in the circuit is: R1 / a;

[0051] The total length of the wire core 2 in the circuit is: R1 / ab;

[0052] The buried depth of the groundwater level is: h1 = (R1 / ab) / 2 = R1 / 2ab.

[0053] After the groundwater level drops, the measured resistance value is R2. At this time, the buried depth of the groundwater level is h2 = R2 / 2ab. Between the two measurements, the change value of the groundwater level is h2 - h1 = (R2 - R1) / 2ab.

[0054] (1) Layout of measuring points:

[0055] During the construction process of underground engineering, a variety of monitoring holes need to be arranged around the construction area, such as soil inclinometers and soil layer settlement. After the holes are drilled, the measuring line in the present invention can be tied to the outside of the soil inclinometer tube or the layer settlement tube, and tied along the tube body as much as possible, and then inserted vertically into the soil along with the tube body.

[0056] If the soil particles in the formation are finer, some cotton balls or paper balls also need to be stuffed at the water inlet hole 5 to prevent a large amount of sediment from entering the conductive gap 4 and accumulating, generating capillary water absorption effect, resulting in inaccurate measurement results.

[0057] After the tube body is inserted to the bottom of the hole, cut off the redundant monitoring wire on the ground, introduce the remaining wire head of the inclinometer into the junction box, and protect it properly.

[0058] (2) Taking the initial value:

[0059] After the measuring point is buried, use an ohmmeter, connect its two poles to the two measuring lines () of the monitoring wire respectively, read the resistance value at this time, and record it as the initial value R1; according to the formula in the measurement principle, the groundwater level at this time is h1 = R1 / 2ab;

[0060] (3) Subsequent on-site measurement:

[0061] During the construction process of underground engineering, numerical data is collected according to the specified monitoring frequency. The collection method is the same as that of the initial value. Read the resistance value at this time and record it as R2; the groundwater level at this time is h2 = R2 / 2ab.

[0062] (4) Calculation of measurement results:

[0063] From the two measurements before and after, the change value of the groundwater level can be obtained as h2 - h1 = (R2 - R1) / 2ab.

[0064] (5) Maintenance of measuring points:

[0065] Keep the end of the measuring line in the junction box during daily operation, hang a signboard, and prohibit pulling forcefully to avoid the wire being pulled.

Claims

1. A monitoring device for the groundwater level during construction, characterized in that, The monitoring device is used to be vertically inserted into the inclinometer hole or the soil layer settlement hole of the soil mass, and is tied outside the inclinometer tube or the layer settlement tube of the soil mass, and is vertically inserted into the bottom soil along with the corresponding tube; it includes: Two parallel and spaced-apart measuring lines, each of the measuring lines includes a wire core (2), the two wire cores (2) are parallel to each other and are both made of non-conductive materials; A resistance wire (1) is spirally wound along the length direction on each of the wire cores (2), each of the resistance wires (1) is closely attached to the corresponding wire core (2), and the ends of the two resistance wires (1) are both used to connect wires; A wire shell (3) is coaxially sleeved outside each of the measuring lines, and each of the wire shells (3) is a cylindrical body with both ends closed; the wire shell (3) is made of hard plastic insulating material; A conductive gap shell body is integrally connected between the two wire shells (3), and the length of the conductive gap shell body is the same as the length of each of the wire shells (3); the inner cavity of the conductive gap shell body is a conductive gap (4), and the conductive gap (4) is communicated with the inner cavities of the two wire shells (3); the width of the conductive gap shell body is less than 5 mm; On the conductive gap shell body, a plurality of water inlet holes (5) are spaced apart along its length direction, which are used to allow the water in the formation to flow into the conductive gap (4) and be introduced into the inner cavities of the two wire shells (3) through the conductive gap (4).

2. The monitoring device for the groundwater level during construction according to claim 1, characterized in that, The conductive gap shell body is in the shape of a cuboid, and its length is consistent with the lengths of the two wire shells (3).

3. The monitoring device for the groundwater level during construction according to claim 1 or 2, characterized in that, On each of the wire cores (2), the winding pitch of the resistance wire (1) is equal.

4. The monitoring device for the groundwater level during construction according to claim 1 or 2, characterized in that, The two resistance wires (1) are made of the same material, have the same length, and have the same winding method.

5. A method for monitoring the groundwater level during construction, characterized in that, Using the monitoring device for the underground water level during the construction process according to any one of claims 1-4, the method is as follows: Step 1: Vertically bury the monitoring device in the soil mass; Step 2: Take the initial value: Connect the wires at the ends of the two resistance wires (1) to the two measuring needles of the ohmmeter respectively, and the initial resistance value measured by the ohmmeter is R1; calculate the initial underground water level depth as: h1 = R1 / 2ab; Remove the ohmmeter; Step 3: Monitor again: During the construction process, when monitoring again according to the construction monitoring frequency, connect the wires at the ends of the two resistance wires (1) to the two measuring needles of the ohmmeter respectively, and the resistance value R2 is measured by the ohmmeter at this time; Remove the ohmmeter; calculate the underground water level depth at this time as: h2 = R2 / 2ab; Wherein: a is the resistance value per unit length of the resistance wire (1); b is the ratio of the length of the resistance wire 1 to the length of the wire core (2). L is the length of one turn of the resistance wire (1) winding, S is the winding pitch, and d is the diameter of the wire core (2).

6. The monitoring method of the groundwater level during the construction process according to claim 5, wherein, It further includes: Step 4: Calculate the change value of the underground water level from the underground water level depths in Step 2 and Step 3 as: h2 - h1 = (R2 - R1) / 2ab.

7. A method for monitoring the groundwater level during construction according to claim 6, characterized in that, Cotton balls or paper balls are stuffed at the water inlet holes (5) to block and filter sediment.

8. A method for monitoring the groundwater level during construction according to claim 7, characterized in that, The buried length of the measuring line is greater than the maximum change depth of the underground water level.

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