Sampler and sampling method for ground improvement bodies

Abstract

To provide a sampler for a soil improvement body and a sampling method which take advantage of a procedure of a backfilling construction of a construction hole, facilitate installation and extraction, and can collect a sample in a desired state.SOLUTION: A sampler includes: an inner pipe 1; and an outer pipe 2 having an external diameter larger than an external diameter of the inner pipe 1 and forming a double pipe along with the inner pipe 1. A lowermost part of a gap V between the inner pipe 1 and the outer pipe 2 in an axial direction is closed. The inner pipe 1 separably couples a first inner pipe 11 with a second inner pipe 12 in order from a lower side so as to penetrate in the axial direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sampler for collecting a ground improvement body for backfilling a construction hole generated after pulling out an existing pile buried in the ground, and a sampling method for the ground improvement body using the sampler, for example.

Background Art

[0002] Conventionally, sampling for geological surveys aims to observe the ground required for the design and construction of structures such as multi-family residential buildings and buildings, or to conduct tests in laboratories. In order to collect the ground sample in as undisturbed a state as possible, for example, a fixed piston type thin-wall sampler, a rotary double-tube sampler (Denison), a rotary triple-tube sampler (Triple), and a core pack tube sampler have been selected according to the soil properties, geological characteristics, hardness and softness, and contaminants.

[0003] For example, Patent Document 1 discloses a sampling apparatus including: a double-tube rod composed of an outer tube rod that transmits press-fitting force and an inner tube rod that transmits rotational force; an inner tube supported while coupled to the lower end of the outer tube rod to accommodate a ground sample; a rotatable outer tube positioned outside the inner tube; a piston that slides axially inside the inner tube; and a gear mechanism that transmits the rotation of the inner tube rod to the outer tube. During sampling, the inner tube does not rotate and the piston continues to press against the ground, so the effect of collecting a sample with little disturbance can be expected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, rotary-type double-pipe samplers with built-in sleeves, such as those described in Patent Document 1, are suitable for deep mixed ground improvement bodies with relatively high strength, as ground improvement bodies from which the entire core is extracted by all-core boring. They are not suitable for backfilling ground improvement soil with relatively low strength, which is required to be at a similar level to the strength of the surrounding ground when filling construction holes after the extraction of existing piles during the reconstruction of buildings such as apartment complexes.

[0006] In other words, the soil used for backfilling tends to be soil with significant differences in hardness depending on the depth direction (axial direction). Therefore, with the above-mentioned sampler, not only is it difficult to appropriately sample the material according to these differences, but because the cylindrical sample is extracted by rotating and drilling, vibrations and shocks during drilling are easily transmitted to the sample, resulting in the sampled material being in a disordered state with many cracks, fissures, peeling, and fractures.

[0007] Generally, the above backfill soil is measured by its deformation modulus, soil strength (N-value), and unconfined compressive strength (N / mm²). 2 The mixture is produced using a formula determined based on the characteristics of the surrounding ground, and its properties are investigated by taking a sample after it has been filled into the construction hole and cured for approximately 28 days. However, the inventors have discovered that if a sampler is installed immediately after filling, when the fluidity is high and there is little difference, and the sampler is removed after curing without drilling, a sample with less disturbance can be obtained.

[0008] Therefore, the object of the present invention is to provide a sampler and sampling method for a ground improvement body that utilizes the procedures for backfilling construction holes, is easy to install and remove, and can collect samples in a desired state. [Means for solving the problem]

[0009] In other words, the sampler for the ground improvement body in the present invention comprises an inner pipe and an outer pipe having an inner diameter larger than the outer diameter of the inner pipe and forming a double pipe together with the inner pipe, wherein the lowest part of the gap between the inner pipe and the outer pipe in the axial direction is closed, and the inner pipe is characterized in that it penetrates in the axial direction and separates the first inner pipe and the second inner pipe from the bottom in order.

[0010] Furthermore, the sampler further comprises a first socket located at the lowest end and connected to the inner tube and the outer tube, wherein the first socket has a socket tip having an opening approximately the same diameter as the inner tube, and a socket expansion portion provided outward from the socket tip so as to be approximately the same diameter as the outer tube, and it is desirable that the socket tip is connected to the first inner tube and the socket expansion portion is connected to the outer tube.

[0011] Furthermore, it is desirable that the sampler also comprises a second socket that fits together the connecting portions of the first inner tube and the second inner tube.

[0012] Furthermore, the present invention relates to a method for sampling a ground improvement material for filling construction holes using the above-mentioned sampler, characterized in that the sampler is inserted to a predetermined depth into the ground improvement material immediately after filling the construction hole, the ground improvement material is poured inward from the lower side of the inner pipe by the insertion of the sampler, and the second inner pipe is withdrawn together with the ground improvement material that has been poured inward and hardened.

[0013] Furthermore, as part of the sampling method described above, it is desirable to inject water into the gap between the inner tube and the outer tube at the same time as inserting the sampler. [Effects of the Invention]

[0014] According to the sampler and sampling method for ground improvement bodies of the present invention, installation and removal are easy, taking advantage of the procedures for backfilling construction holes, and samples in a desired state can be collected. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram illustrating the use of a sampler for a ground improvement body in one embodiment of the present invention. [Figure 2] The above sampler is shown in (a) before assembly and (b) after assembly. [Figure 3] This is a flowchart illustrating the sampling method for ground improvement structures using the sampler described above. [Modes for carrying out the invention]

[0016] The sampler and sampling method for a ground improvement body in one embodiment of the present invention will be described below with reference to Figures 1 to 3. In these diagrams, in cases where multiple identical parts exist, only one part is numbered. For ease of explanation, some parts are shown in cross-sectional views, and designated parts or their leader lines are shown with hidden lines (dashed lines) or imaginary lines (dotted lines). In the explanation, terms indicating direction such as up, down, side, vertical, vertical, horizontal, outward, and inward are generally based on the ground surface, and other reference points will be indicated as appropriate.

[0017] As shown in Figure 1, the ground improvement sampler S in the present invention samples ground improvement material (backfill soil) Gb for backfilling construction holes that are created after existing piles of a demolished apartment building or the like have been pulled out of the ground Ga. The existing piles are, for example, PC piles with a diameter of 0.3m and a length of 15m that were driven into the ground Ga using the press-in method, and the construction holes are corresponding to the size of the existing piles.

[0018] The ground improvement body Gb is, for example, a cement-bentonite improved soil obtained by mixing bentonite and cement grout in a predetermined ratio, and may also be used as a self-hardening stabilizing fluid. The uniaxial compressive strength of the soil layer composed of the ground improvement body Gb may be calculated by substituting the strength of the soil layer (target value) of ground Ga into the relationship between the strength of the soil layer and the uniaxial compressive strength, which is set in consideration of the variation in strength due to the ratio and mixing method described above, as well as the coefficient related to safety.

[0019] The sampler S includes an inner tube 1, and an outer tube 2 having an inner diameter larger than the outer diameter of the inner tube 1 and forming a double tube together with the inner tube 1. The lowermost part of the gap V between the inner tube 1 and the outer tube 2 in the axial direction is closed, and the inner tube 1 is axially penetrated to separably connect a first inner tube 11 and a second inner tube 12 in order from the lower side. The lowermost part of the gap V may be closed with a predetermined plate material, welding, or the like.

[0020] According to this configuration, when the sampler S is inserted into the ground improvement body Gb immediately after backfilling into a construction hole, the ground improvement body Gb flows inward from the lower end opening of the inner tube 1, while does not flow into the gap V between the inner tube 1 and the outer tube 2. As the second inner tube 12 is separated from the first inner tube 11 and pulled out together with the hardened ground improvement body Gb, no vibration or impact caused by operations such as drilling occurs, so the effect of collecting the ground improvement body Gb in the second inner tube 12 as a sample in a state with little disturbance can be expected. The ground improvement body Gb serving as the sample corresponds to the height H in the second inner tube 12, enabling continuous sampling in the depth direction.

[0021] Further, the sampler S further includes a first socket 3 located at the lowermost end in the axial direction and connected to the inner tube 1 and the outer tube 2. The first socket 3 has a socket tip portion 31 having an opening with substantially the same diameter as the inner tube 1, and a socket expanding portion 32 provided outward from the socket tip portion 31 so as to have substantially the same diameter as the outer tube 2. The socket tip portion 31 is connected to the first inner tube 11, and the socket expanding portion 32 is connected to the outer tube 2.

[0022] According to this configuration, a desired double tube structure can be formed by the inner tube 1 and the outer tube 2 using the first socket 3 as a base, so the sampler S can be easily manufactured. That is, a structure in which the ground improvement body Gb is poured into the inner side of the first inner tube 11 via the socket tip portion 31 and the lowermost part of the gap V is closed by the socket expanding portion 32 can be formed, so it is only necessary to assemble the pre-processed inner tube 1, outer tube 2, and first socket 3 at the construction site, and improvement in work efficiency can also be expected.

[0023] Further, the sampler S further includes a second socket 4 that fits the connecting portions of the first inner tube 11 and the second inner tube 12 to each other.

[0024] With this configuration, since the first inner pipe 11 and the second inner pipe 12 are simply fitted into the second socket 4 and connected, the second inner pipe 12 can be separated from the first inner pipe 11 simply by pulling it out, which is expected to make it easier to sample the ground improvement body Gb.

[0025] Next, we will explain the details of sampler S using Figure 2.

[0026] The material of sampler S is polyvinyl chloride, but other thermoplastic resins or metals may be used as long as they have the desired strength, and the second inner tube 12 is particularly preferably lightweight and easy to cut. The diameter of inner tube 1 may be approximately 60 mm outer diameter and 50 mm inner diameter, and the diameter of outer tube 2 may be approximately 90 mm outer diameter and 80 mm inner diameter, and there is no limit to the material as long as there is a predetermined axial gap when inner tube 1 is inserted into outer tube 2 to form a double tube.

[0027] The inner pipe 1 and outer pipe 2 penetrate axially and have openings at their upper and lower ends, and their lengths may be equal or different. The first inner pipe 11 is shorter than the second inner pipe 12, and its length may be about 20 cm. The first inner pipe 11, the second inner pipe 12, or the outer pipe 2 may be a single pipe, or multiple pipes of a predetermined size (e.g., in 1m units) connected to match the depth of the construction hole, and may be connected by welding or adhesive, or by threads (male threads and female threads) cut into each connection part.

[0028] The first socket 3 is for joining the inner pipe 1 and the outer pipe 2, and it is sufficient that the ground improvement soil Gb is poured into the inside of the inner pipe 1 but not into the gap between the inner pipe 1 and the outer pipe 2, and its shape, dimensions, and the above-mentioned joint structure are not limited. The socket tip 31 and the first inner pipe 11, and the socket expansion part 32 and the outer pipe 2 may be fixed and connected by welding or adhesive, or they may be connected by threads (male threads and female threads) cut into each connecting part.

[0029] The second socket 4 is, for example, a cylinder having an inner diameter slightly larger than the outer diameter of the first inner tube 11 and the second inner tube 12, and can be tightly fitted to the inside of the first inner tube 11 and the second inner tube 12 and can be inserted and removed freely. Its shape and dimensions are not limited.

[0030] The assembly method for sampler S is as shown in Figure 2(a). First, the socket tip 31 of the first socket 3 is connected to the first inner tube 11 of the inner tube 1. Next, the first inner tube 11 and the second inner tube 12 are connected via the second socket 4. After that, the socket expansion part 32 is connected to the outer tube 2 to form the shortest possible sampler unit. Subsequently, depending on the depth of the construction hole, multiple parts of the second inner tube 12 and the outer tube 2 are connected to form sampler S as shown in Figure 2(b).

[0031] Next, Figure 3 will be used to explain the sampling method for ground improvement bodies using sampler S.

[0032] First, as shown in Figure 3(a), the sampler S is inserted to a predetermined depth into the ground improvement material Gb immediately after filling the construction hole in the ground Ga. Next, as shown in Figure 3(b), the insertion of the sampler S causes the ground improvement material Gb to flow inward from the lower side of the inner pipe 2 through the opening of the socket tip 31 of the first socket 3. Then, as shown in Figure 3(c), the second inner pipe 12 is withdrawn from the second socket 4 along with the ground improvement material Gb that has flowed inward and hardened.

[0033] According to this method, the ground improvement material Gb immediately after filling has high fluidity and little difference in hardness in the depth direction, and flows inward from the bottom of the inner pipe 2, making it easy to insert the sampler S into the ground improvement material Gb and easy to fill the second inner pipe 12 to the desired height. Furthermore, the second inner pipe 12 can be easily separated by the second socket 4, and since there is no need to drill or otherwise remove the hardened ground improvement material Gb, it is possible to expect the effect of easily collecting a sample in a nearly undisturbed state. That is, as shown in Figure 3(d), after dividing the second inner pipe 12 into parts pipe units together with the sample, the second inner pipe 12 can be peeled off by making cuts in two places in the axial direction with a cutting machine or the like, so that the contents can be easily removed without damaging them, and the sample can be separated according to the depth from the ground surface.

[0034] Furthermore, as shown in Figure 3(b), water W is injected into the gap V between the inner pipe 1 and the outer pipe 2 as the sampler S is inserted. The water W may be injected in multiple stages from the ground by workers or other personnel, adjusting the amount as needed.

[0035] According to this method, if buoyancy is generated in the sampler S from the ground improvement body Gb, the water W injected into the void V can be used as a weight, which is expected to make it easier to insert the sampler S.

[0036] Furthermore, as shown in Figure 3(b), considering the possibility that the ground improvement material Gb may not flow easily into the second inner pipe 12 due to clogging of the opening at the tip of the socket 31, the position of the upper end of the ground improvement material Gb inside the second inner pipe 12 may be measured at the same time as inserting the sampler S. Also, as shown in Figure 3(c), the remaining material after the second inner pipe 12 is withdrawn may be buried together with the additional ground improvement material to be used for backfilling, or it may be removed by a predetermined method.

[0037] Furthermore, the sampler shown in this embodiment is not limited to the above-described content, and includes the position, shape, dimensions, and relationships between any part, as long as equivalent effects can be obtained. [Explanation of Symbols]

[0038] 1 Inner pipe, 11 First inner pipe, 12 Second inner pipe, 3 First socket, 31 Socket tip, 32 Socket expansion section, 4 Second socket, S Sampler, Ga Ground, Gb Ground improvement body, V Void, W Water

Claims

1. An inner tube comprising a first inner tube and a second inner tube detachably connected, An outer tube having an inner diameter larger than the outer diameter of the inner tube, and forming a double tube together with the inner tube, A first socket located at the lowest end and connected to the inner tube and the outer tube, It comprises a second socket that fits the connecting portions of the first inner tube and the second inner tube together, The first socket is, The socket tip portion having an opening of approximately the same diameter as the inner tube, It has a socket expansion portion provided on the outside of the socket tip so as to be approximately the same diameter as the outer tube, The tip of the socket is connected to the first inner tube, The socket expansion portion is connected to the outer tube, The lowest part of the gap between the inner tube and the outer tube in the axial direction is closed. A sampler for a ground improvement body characterized by the following features.

2. The socket expansion portion is tapered The sampler according to feature 1.

3. A method for sampling a ground improvement body for filling construction holes using the sampler described in Claim 1 or 2, Insert the sampler into the ground improvement body immediately after filling the construction hole to a predetermined depth. By inserting the sampler, the ground improvement material is poured into the inside of the inner pipe from the lower side. The second inner pipe is withdrawn from the second socket along with the ground improvement material that has been poured inside and hardened. A method for sampling a ground improvement body, characterized by the following features.

4. As the sampler is inserted, water is injected into the gap between the inner tube and the outer tube. A method for sampling a ground improvement body according to feature 3.

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