Device suitable for combined measurement of pore water pressure and underground water level of soft soil stratum

Abstract

The utility model relates to the technical field of soft soil stratum pore water pressure and underground water level testing, and particularly discloses a soft soil stratum pore water pressure and underground water level combined testing device which comprises a water level pipe, a plurality of water permeable holes are formed in the middle of the water level pipe, and a filter screen ring is arranged on the outer side of the water level pipe and used for filtering the water permeable holes. The outer side of the water level pipe is fixedly connected with an osmometer; and the osmometer is bound on the water level pipe through a binding belt. The device has the beneficial effects that the osmometer is fixed on the outer side of the water level pipe, and the osmometer and the water level pipe are inserted into the hole, so that the pore water pressure and the underground water level can be measured in one hole; the device can monitor the pore water pressure of a single hole at different depths and multiple points, also can obtain the dynamic change of the underground water level corresponding to the measuring hole, and improves the reliability of monitoring data through mutual verification.

Description

Technical Field

[0001] The utility model relates to the technical field of pore water pressure and groundwater level testing in soft soil strata, and particularly relates to a device applicable to the combined measurement of pore water pressure and groundwater level in soft soil strata. Background Technique

[0002] In coastal areas with deep soft soil, due to the high groundwater level, large tidal influence on water level changes, uneven changes in the thickness of soft soil layers, complex formation structures, and large variations in soil conditions, the variation laws of pore water pressure vary greatly in different planes at the same vertical depth. In addition, due to the characteristics of soft soil such as low bearing capacity and high compressibility, when constructing buildings or structures on soft foundations, ground treatment needs to be carried out first, and the dissipation of pore water pressure is an important indicator of soft foundation consolidation change. It can be seen that when excavating soil in soft soil areas, pore water pressure and groundwater level are one of the very important monitoring items. To truly reflect the actual situation on site, the embedding quality of the measuring elements plays a decisive role in the quality of test results. At present, most scholars mainly study the variation characteristics of pore water pressure at different depths and positions by single-hole embedding of a single piezometer. Its test data lacks strict comparability, has certain deviations, and has a large number of drill holes, large engineering quantities, and high costs. At the same time, due to multiple disturbances of the soil layer, it is easy to cause structural changes in the undisturbed soil and affect the monitoring results. In addition, a small number of scholars embed two piezometers through one drill hole, but due to the extremely easy shrinkage of the soft soil stratum or floating slurry in the hole, problems such as the piezometer not being embedded in place or loosening and offset occurring, resulting in distorted test data. Therefore, the research on the combined measurement of pore water pressure and groundwater level in soft soil strata has practical significance. Content of the Utility Model

[0003] The purpose of the utility model is to solve the shortcomings existing in the prior art, and to propose a device applicable to the combined measurement of pore water pressure and groundwater level in soft soil strata.

[0004] In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0005] A device applicable to the combined measurement of pore water pressure and groundwater level in soft soil strata includes a water level pipe. Multiple water permeable holes are arranged in the middle of the water level pipe. A filter net ring is arranged outside the water level pipe, and the filter net ring is used to filter the water permeable holes. A piezometer is fixedly connected to the outside of the water level pipe, and the piezometer is tied to the water level pipe through a binding band.

[0006] Preferably, two limiting strips are arranged on the water level pipe, and the binding band is located between the two limiting strips, and the two limiting strips can limit the binding band.

[0007] Preferably, a bottom plate is arranged at the bottom of the water level pipe, and multiple through holes are arranged on the bottom plate.

[0008] Preferably, the upper side of the bottom plate is hinged to the cover plate through a hinge, and when the cover plate fits with the bottom plate, all the through holes can be sealed.

[0009] Preferably, a cross beam is fixedly connected inside the water level pipe. A guide hole is provided on the cross beam. A pressure rod is slidably connected inside the guide hole. The lower side of the pressure rod is fixedly connected to a pressure plate. The cover plate can be pressed tightly through the pressure plate so that the cover plate is in a fitting state with the bottom plate. A pull rope is fixedly connected between the pressure plate and the cover plate.

[0010] Preferably, the upper end of the water level pipe is coaxially and fixedly connected to an end seat.

[0011] The beneficial effects of the present utility model: An apparatus for jointly measuring pore water pressure and groundwater level applicable to soft soil strata provided by the utility model fixes a piezometer on the outer side of the water level pipe. The piezometer and the water level pipe are inserted into the hole together. In this way, the measurement of the magnitude of pore water pressure and the groundwater level situation can be realized in one hole. It can not only monitor the pore water pressure at multiple points at different depths in a single hole, but also obtain the dynamic change of the groundwater level corresponding to the measuring hole. The two confirm each other, improving the reliability of the monitoring data. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is the basic structure diagram of an apparatus for jointly measuring pore water pressure and groundwater level applicable to soft soil strata provided by the present utility model;

[0013] Figure 2 is Figure 1 the enlarged view of part A of

[0014] Figure 3 is Figure 1 the enlarged view of part W of DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] In order to make the purpose, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0016] As Figures 1 - 3 shown, an apparatus for jointly measuring pore water pressure and groundwater level applicable to soft soil strata provided in this embodiment includes a water level pipe 1. The water level pipe 1 is made of PVC pipe. The upper end of the water level pipe 1 is coaxially and fixedly connected to an end seat 4. The diameter of the end seat is larger than the diameter of the water level pipe 1. In this way, after the water level pipe 1 is inserted into the soft soil strata, the end seat 4 can remain on the upper surface of the soft soil strata. Corresponding measures can be taken to reinforce the end seat 4, thereby indirectly reinforcing the water level pipe 1 and improving the stability of the water level pipe 1 to prevent the water level pipe 1 from shifting.

[0017] A plurality of water permeable holes 11 are provided in the middle of the piezometer tube 1, and a filter net ring 2 is provided outside the piezometer tube 1. The filter net ring 2 is used to filter the water permeable holes 11 to prevent soil from entering the piezometer tube 1 through the water permeable holes 11. At the same time, the water in the soft soil layer will slowly seep into the piezometer tube 1 through the water permeable holes 11. After inserting a water level gauge into the piezometer tube 1, the water level in the piezometer tube 1 can be measured, and then the groundwater level of the soft soil layer can be calculated.

[0018] An osmotic pressure gauge 5 is fixedly connected to the outside of the piezometer tube 1, and the osmotic pressure gauge 5 is tied to the piezometer tube 1 by a binding band 6. The osmotic pressure gauge 5 can measure the pore water pressure of the soft soil layer. Two limiting strips 61 are provided on the piezometer tube 1, and the binding band 6 is located between the two limiting strips 61. The binding band 6 can be limited by the two limiting strips 61. Prevent the binding band 6 from moving up and down, so as to ensure that the position of the osmotic pressure gauge 5 will not move.

[0019] A bottom plate 3 is provided at the bottom of the piezometer tube 1. A plurality of through holes 31 are provided on the bottom plate 3. The water in the soft soil layer enters the piezometer tube 1 through the through holes 31, and a filter net is arranged in the through holes 31. In order to prevent the soil of the soft soil layer from entering the piezometer tube 1 through the through holes 31 when inserting the piezometer tube 1. The upper side of the bottom plate 3 is hinged with a cover plate 32 by a hinge. When the cover plate 32 is attached to the bottom plate 3, all the through holes 31 can be sealed. A cross beam 33 is fixedly connected inside the piezometer tube 1. A guide hole is provided on the cross beam 33. A pressure rod 34 is slidably connected in the guide hole. The lower side of the pressure rod 34 is fixedly connected with a pressure plate 35. The cover plate 32 can be pressed tightly by the pressure plate 35 so that the cover plate 32 is in a fitting state with the bottom plate 3. A pull rope 36 is fixedly connected between the pressure plate 35 and the cover plate 32. When inserting the piezometer tube 1 into the soft soil layer, the cover plate 32 is pressed tightly by the pressure plate 35. When the piezometer tube 1 is inserted to the specified depth, the pressure rod 34 is lifted upward, so that the pressure rod 34 drives the pressure plate 35 to move upward. Since the pull rope 36 is arranged between the pressure plate 35 and the cover plate 32, when the pressure plate 35 rises, the cover plate 32 will rotate around the hinge under the action of the pull rope, so that the water in the soft soil layer will slowly seep into the piezometer tube 1, which is convenient for water level measurement.

[0020] When the device for jointly measuring the pore water pressure and the groundwater level in the soft soil layer provided in this embodiment is in use, installation is required first, and the installation steps are as follows:

[0021] Step 1: According to the on-site hydrogeological conditions, find out the thickness of the soft soil layer and the occurrence of groundwater, and select appropriate osmotic pressure gauges and water level gauges to ensure the test accuracy;

[0022] Step 2: Use a mechanical drilling method to drill a hole, and the drilling depth is greater than the maximum designed burial depth of the osmotic pressure gauge by 1.0 m;

[0023] Step 3: Use the supporting PVC plastic water level pipe as the positioning and guiding auxiliary device for the piezometer installation. According to the designed burial depth position of the piezometer, drill two pairs of screws symmetrically on the outer wall of the water level pipe at the pre-burial position to form positioning grooves, and tie and fix the piezometer along the grooves with iron wire;

[0024] Step 4: Wrap the outer guiding wire of the piezometer tightly with waterproof tape to ensure that the piezometer can be smoothly lowered along with the water level pipe, and avoid damage or breakage of the cable;

[0025] Step 5: Adopt the pressing-in burial method. Backfill 0.5 m thick medium and coarse sand in the hole, lower the water level pipe with a piezometer installed at the bottom end, and then slowly and evenly put bentonite balls into the hole until 0.5 m above the position of the second piezometer, and backfill medium and coarse sand. In order to reduce the influence of mud buoyancy during the lowering process of the water level pipe, slowly inject water into the pipe to increase the gravity, and repeat this process until all piezometers are installed;

[0026] Step 6: Fill and seal tightly with water-proof filler within the range of 0.5 - 1.0 m from the end of the pipe mouth to prevent surface water from seeping in, and set up effective protective devices to complete the installation of the piezometer and the water level pipe.

[0027] The piezometer selected is the JMZX-5503HAT intelligent vibrating wire digital piezometer, with a test range of 0.3 MPa, a sensitivity of 0.001 MPa, a maximum diameter of 30 mm, and a length of 130 mm. To ensure the smoothness of the water inlet of the piezometer, it is wrapped with a self-made sandbag made of a relatively dense nylon mesh to prevent mud blockage. The water level gauge selected is the SWJ-80 steel tape water level gauge, with a measuring depth of 30 m, a minimum reading of 1.0 mm, a repeatability reading of ±2.0 mm, and an instrument weight of 3.5 kg; the water level pipe selected is a φ50 mm PVC plastic water level pipe, and the pipe length specifications are 2 m and 4 m. The specific pipe length is reasonably matched according to the designed burial depth of the piezometer. This method effectively solves the problems such as a large number of drilling holes, difficult piezometer positioning, floating slurry blockage, easy hole shrinkage, and easy deviation during the monitoring of pore water pressure and groundwater level, and is applicable to the installation and monitoring of test elements for the combined measurement of pore water pressure and groundwater level in soft soil areas such as deep silt. Through the above method, the functions of "multiple gauges in one hole and dual use of one hole" are realized. It can not only monitor the pore water pressure at multiple points at different depths in a single hole, but also obtain the dynamic changes of the groundwater level corresponding to the measuring hole, which can confirm each other, improve the accuracy of the monitoring data. At the same time, this method has the advantages of simple operation, accurate positioning, high use efficiency, low cost, safety and reliability, and has good engineering application value.

Claims

1. An apparatus for jointly measuring pore water pressure and groundwater level applicable to soft soil strata, characterized in that: It includes a water level pipe (1). A plurality of water permeable holes (11) are provided in the middle of the water level pipe (1). A filter net ring (2) is provided outside the water level pipe (1). The filter net ring (2) is used to filter the water permeable holes (11). An osmometer (5) is fixedly connected to the outside of the water level pipe (1). The osmometer (5) is tied to the water level pipe (1) by a binding band (6).

2. The device for jointly measuring pore water pressure and groundwater level applicable to soft soil strata according to claim 1, wherein: Two limiting strips (61) are provided on the water level pipe (1). The binding band (6) is located between the two limiting strips (61). The binding band (6) can be limited by the two limiting strips (61).

3. The device for jointly measuring pore water pressure and groundwater level applicable to soft soil stratum according to claim 1, wherein: A bottom plate (3) is provided at the bottom of the water level pipe (1). A plurality of through holes (31) are provided on the bottom plate (3).

4. The device for jointly measuring pore water pressure and groundwater level applicable to soft soil stratum according to claim 3, wherein: A cover plate (32) is hinged to the upper side of the bottom plate (3) through a hinge. When the cover plate (32) fits with the bottom plate (3), all the through holes (31) can be sealed.

5. An apparatus for jointly measuring pore water pressure and groundwater level applicable to soft soil strata, as claimed in claim 4, wherein: A cross beam (33) is fixedly connected inside the water level pipe (1). A guide hole is provided on the cross beam (33). A pressure rod (34) is slidably connected inside the guide hole. A pressing plate (35) is fixedly connected to the lower side of the pressure rod (34). The cover plate (32) can be pressed tightly by the pressing plate (35) so that the cover plate (32) is in a state of fitting with the bottom plate (3). A pulling rope (36) is fixedly connected between the pressing plate (35) and the cover plate (32).

6. The device for jointly measuring pore water pressure and groundwater level applicable to soft soil strata according to claim 1, characterized in that: A end seat (4) is coaxially and fixedly connected to the upper end of the water level pipe (1).

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