Method for collecting large-size undisturbed loess sample

Abstract

The invention belongs to the technical field of loess research, and particularly relates to a method for collecting a large-size undisturbed loess sample. The technical problems that the size of an undisturbed soil sample collected by an existing loess undisturbed sample collecting method is small, and a large undisturbed loess simulation test is difficult to carry out indoors are solved. Comprising the following steps: selecting a relatively flat site, and marking a sample collection area and a peripheral operation channel; marking the positions of the sample, the temporary support and the bottom operation area on the loess bulk sample; digging through a bottom operation area along the short edge direction of the loess bulk sample, and sequentially putting a high-density foam base plate and a tray base; a hoisting steel pipe is placed in a framework gap at the lower part of a tray base, and hoisting equipment is selected according to field reality and sample weight; during hoisting, synchronously stripping soil in hoisting cutting areas at two ends of the sample by using a shovel or a rope saw, so that the sample is gradually separated from the temporary support; after being completely stripped, the sample is moved to a flat position by a crane and is timely wrapped and sealed by a plastic film to prevent moisture loss of the sample.

Description

Technical Field

[0001] The present invention belongs to the technical field of loess research, and particularly relates to a method for collecting large-size undisturbed loess samples. Background Art

[0002] In the research on geological disaster prevention and control and ecological environment restoration, it is often necessary to collect undisturbed loess samples for experimental analysis. With the increase in the number of experimental projects and the improvement of experimental accuracy, the requirements for the size of undisturbed loess samples are also getting larger and larger. Due to the short sedimentation age, low strength, and loose and brittle texture of loess, it is difficult to collect large-size undisturbed soil samples. At present, most of the collection of undisturbed loess samples adopts the simple method of manually excavating the surrounding of the soil body, wrapping it with plastic cloth and tape, and then turning over and trimming the bottom surface of the soil sample. The size of the collected undisturbed soil sample is small, and it is difficult to carry out large-scale undisturbed loess simulation tests indoors. The large-size undisturbed loess sample has a large self-weight, is difficult to turn over completely, and the enclosure strength of wrapping with plastic cloth and tape is also insufficient, making it difficult to transport over long distances. Summary of the Invention

[0003] In order to solve the technical problem that the size of the undisturbed loess sample collected by the current method for collecting undisturbed loess samples is small and it is difficult to carry out large-scale undisturbed loess simulation tests indoors, the present invention provides a method for collecting large-size undisturbed loess samples.

[0004] The present invention is implemented by the following technical solutions: A method for collecting large-size undisturbed loess samples, comprising the following steps: 1) Select a relatively flat site. After stripping and trimming the topsoil of the site, mark the sample collection area and the surrounding operation passage around the sample collection area; 2) Dig the surrounding operation passage to a certain distance below the bottom surface of the sample, and form a cuboid large loess sample in the middle; 3) In the long side direction of the large loess sample, mark the positions of the sample, the temporary support, and the bottom operation area according to the sample specifications. The bottom operation area is located below the sample and extends beyond both ends of the long side of the large loess sample in the length direction; 4) After digging through the bottom operation area along the short side direction of the large loess sample, sequentially place a high-density foam cushion board and a tray base, and immediately use temporary support to tightly attach the high-density foam cushion board and the tray base 7 to the bottom of the sample to prevent the sample from collapsing; There is a skeleton gap between the bottom of the tray base and the temporary support; 5) Sequentially place high-density foam cushion boards and side protection plates with keels on both sides in the short side direction of the sample, place a top lifting support plate on the top, and line it with a high-density foam cushion board; Place the lifting steel pipe in the skeleton gap under the tray base, then pass the sling through the lifting steel pipe, select a suitable lifting device according to the actual situation on site and the weight of the sample, and install a tensiometer between the lifting device and the sling to facilitate controlling the pulling force; 6) Before hoisting, first pre-tighten the sling with a pulling force greater than the weights of the hoisting equipment such as the pallet base, high-density foam cushion plate, side guard plate with keel, and hoisting steel pipe, so that the pallet base closely adheres to the bottom of the sample, playing a certain supporting role; 7) During hoisting, use a shovel or a rope saw to synchronously strip the soil at the hoisting cutting areas at both ends of the sample, so that the sample is gradually separated from the temporary support, and gradually increase the pulling force of the sling according to the stripping progress, so that the pulling force of the sling is relatively balanced with the weight of the stripped part of the sample, avoiding damage to the sample due to stress change during the stripping process; 8) After the sample is completely stripped, use a crane to move it to a flat position. After trimming the periphery of the sample smoothly, promptly wrap and seal it with a plastic film to prevent moisture loss of the sample.

[0005] Step 9): Install high-density foam cushion plates and packaging boards around and on the top of the sample in sequence, and fix them together with the bottom pallet base; when bundling with binding straps, appropriately increase the pulling force to make the packaging board closely adhere to the sample to prevent the sample from being damaged by shaking during transportation.

[0006] In step 1), the width of the peripheral operation passage is 0.6 - 0.8 m.

[0007] In step 2), dig the peripheral operation passage to at least 0.5 m below the bottom surface of the sample 4, and form a cuboid large loess sample with a width of 1.0 m * a height of 1.5 m * a length of 2 m in the middle.

[0008] In step 3), the height of the bottom operation area 6 is 0.4 - 0.5 m.

[0009] The top of the said pallet base is flat, and the bottom is multiple downwardly protruding bosses; the temporary supports (multiple) are in a trapezoidal structure, connecting with the bottom bosses of the pallet base to realize the support for the sample, and a framework gap is formed between the bottom of the pallet base and the temporary supports.

[0010] The present invention utilizes the cohesiveness and shear resistance of undisturbed loess, excavates the bottom operation passage and then places the pallet base; during hoisting, synchronously strip the soil connected to both ends of the sample, so that the sample is gradually separated from the temporary support, and gradually increase the pulling force of the sling according to the stripping progress, so that the pulling force of the sling is relatively balanced with the weight of the stripped part of the sample, avoiding damage to the sample due to stress change during the stripping process.

[0011] The beneficial effects of the present invention compared with the prior art: The process of the present invention can effectively solve the problems of the collection difficulty of large-size undisturbed loess samples and the low success rate of sample collection, provide technical support for carrying out large-scale on-site simulation tests of loess indoors, further studying the formation mechanism of loess geological disasters, and preventing and controlling geological disasters. Description of the Drawings

[0012] Figure 1Schematic diagram of the layout of the operation passage in the present invention.

[0013] Figure 2 Schematic diagram of the excavation of the operation passage in the present invention.

[0014] Figure 3 Schematic diagram of the sample collection position in the present invention.

[0015] Figure 4 Schematic diagram of the installation of the tray base and temporary support in the present invention.

[0016] Figure 5 One of the schematic diagrams of the installation of the hoisting auxiliary facilities in the present invention (front view).

[0017] Figure 6 Two of the schematic diagrams of the installation of the hoisting auxiliary facilities in the present invention (side view).

[0018] Figure 7 Schematic diagram of hoisting and cutting in the present invention.

[0019] 1 - Sample collection area, 2 - Peripheral operation passage, 3 - Large loess sample, 4 - Sample, 5 - Temporary support, 6 - Bottom operation area, 7 - High - density foam cushion plate, 8 - Tray base, 9 - Temporary support, 10 - Tensile meter, 11 - Suspension strap, 12 - Top hoisting support plate, 13 - Side protection plate with keel, 14 - Hoisting steel pipe, 15 - Soil body in the hoisting and cutting area. Detailed implementation manner

[0020] A method for collecting large - sized undisturbed loess samples includes the following steps: 1) Select a relatively flat site. After stripping and leveling the topsoil, mark the sample collection area 1 and the peripheral operation passage 2. The width of the peripheral operation passage 2 is about 0.6 - 0.8 m, as Figure 1 shown.

[0021] 2) Excavate the peripheral operation passage 2 to about 1.5 m (0.5 m below the bottom surface of the sample), and a cuboid large loess sample 3 with a width of 1.0 m * height of 1.5 m * length of 2 m is formed in the middle, as Figure 2 shown.

[0022] 3) Along the long side direction of the large loess sample 3, mark the positions of the sample 4, the temporary support 5 and the bottom operation area 6 according to the sample specifications. The height of the bottom operation area 6 is about 0.4 - 0.5 m, as Figure 3 shown.

[0023] 4) After excavating through the bottom operation area 6 along the short side direction of the large loess sample 3, sequentially place the high - density foam cushion plate 7 and the tray base 8, and promptly use the temporary support 9 to tightly attach the high - density foam cushion plate 6 and the tray base 8 to the bottom of the sample 4 to prevent the sample 4 from collapsing, as Figure 4 shown.

[0024] 5) Place high-density foam pads 7 and keel side guards 13 on both sides of the sample 4, and place the top lifting support plate 12 on the top, lined with high-density foam pads 7. Place the lifting steel pipe 14 in the gap of the lower frame of the pallet base 8, and then insert the lifting belt 11 into the lifting steel pipe 14. Select the appropriate lifting equipment according to the actual situation on site and the weight of the sample. Install a tension meter 10 between the lifting equipment and the lifting belt 11 to facilitate the control of tension, such as Figure 5 , 6 shown.

[0025] 6) Before hoisting, first pre-tighten the sling 11 with a tension slightly greater than the weight of the pallet base, formwork (with keel side guards, high-density foam pads), hoisting steel pipes and other hoisting equipment, so that the pallet is close to the bottom of the sample and plays a certain supporting role.

[0026] 7) During hoisting, use a shovel or rope saw to simultaneously peel off the soil 15 in the hoisting and cutting area at both ends of the sample, so that the sample 4 is gradually separated from the temporary support 3, and gradually increase the tension of the sling according to the progress of the peeling, so that the tension of the sling and the weight of the peeled part of the sample are relatively balanced to avoid damage to the sample due to stress changes during the peeling process, such as Figure 7 shown.

[0027] 8) After the sample is completely peeled off, use a crane to move it to a flat position. After trimming the four sides of the sample to make it flat, wrap and seal it with plastic film in time to prevent moisture loss in the sample.

[0028] 9) Install high-density foam pads 7 and packaging boards around and on the top of the sample, and fix them together with the pallet base at the bottom. When tying with binding tape, increase the tension appropriately to make the packaging board close to the sample to prevent the sample from shaking and being damaged during transportation.

[0029] This embodiment does not impose any formal limitation on the shape, structure, etc. of the present invention. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for collecting large-sized undisturbed loess samples, characterized in that, It includes the following steps: 1) Select a relatively flat site. After stripping and leveling the topsoil of the site, mark the sample collection area (1) and the peripheral operation passage (2) surrounding the sample collection area (1); 2) Dig the peripheral operation passage (2) to a certain distance below the bottom surface of the sample (4), and form a cuboid large loess sample (3) in the middle; 3) In the long side direction of the large loess sample (3), mark the positions of the sample (4), the temporary support (5) and the bottom operation area (6) according to the sample specifications. The bottom operation area (6) is located below the sample (4) and extends beyond both ends of the long side of the large loess sample (3) in the length direction; 4) After digging through the bottom operation area (6) along the short side direction of the large loess sample (3), sequentially place the high-density foam cushion plate (7) and the tray base (8), and promptly use the temporary support (9) to tightly attach the high-density foam cushion plate (7) and the tray base (7) to the bottom of the sample (4) to prevent the sample (4) from collapsing; There is a skeleton gap between the bottom of the tray base (8) and the temporary support (9); 5) Sequentially place the high-density foam cushion plate (7) and the side protection plate with keel (13) on both sides of the short side direction of the sample (4), place the top lifting support plate (12) on the top, and line it with the high-density foam cushion plate (7); Place the lifting steel pipe (14) in the skeleton gap under the tray base (8), then pass the sling (11) through the lifting steel pipe (14), select a suitable lifting device according to the actual situation on site and the weight of the sample, and install a tensiometer (10) between the lifting device and the sling (11) to facilitate controlling the tension; 6) Before hoisting, first pre-tighten the sling (11), and the tension is greater than the weights of these hoisting devices such as the tray base (8), the high-density foam cushion plate (7), the side protection plate with keel (13), and the lifting steel pipe (14), so that the tray base (8) closely adheres to the bottom of the sample (4) to play a certain supporting role; 7) During hoisting, use a shovel or a rope saw to synchronously strip the soil body (15) in the hoisting cutting areas at both ends of the sample (4), so that the sample (4) is gradually separated from the temporary support (3), and gradually increase the tension of the sling (11) according to the stripping progress, so that the tension of the sling (11) is relatively balanced with the weight of the stripped part of the sample (4), and avoid damage to the sample (4) due to stress change during the stripping process; 8) After the sample (4) is completely stripped, use a crane to move it to a flat position. After trimming the four sides of the sample (4) smoothly, promptly wrap and seal it with a plastic film to prevent the loss of moisture in the sample.

2. The collection method of a large-sized undisturbed loess sample according to claim 1, wherein It also includes step 9): Sequentially install the high-density foam cushion plate (7) and the packaging board around and on the top of the sample (4), and fix them together with the bottom tray base (8); When bundling with a binding band, appropriately increase the tension to make the packaging board closely adhere to the sample (4) to prevent the sample (4) from shaking and being damaged during transportation.

3. The method for collecting a large-size undisturbed loess sample according to claim 1 or 2, characterized in that, In step 1), the width of the peripheral operation passage (2) is 0.6 - 0.8 m.

4. The method for collecting a large-sized undisturbed loess sample according to claim 1 or 2, characterized in that, In step 2), dig the peripheral operation passage (2) to at least 0.5 m below the bottom surface of the sample (4), and form a cuboid large loess sample (3) with a width of 1.0 m * a height of 1.5 m * a length of 2 m in the middle.

5. The method for collecting a large-sized undisturbed loess sample according to claim 3, characterized in that, In step 2), the peripheral operation channel (2) is excavated to at least 0.5 m below the bottom surface of the sample (4), and a cuboid loess sample (3) with a width of 1.0 m * a height of 1.5 m * a length of 2 m is formed in the middle.

6. The method for collecting a large-size undisturbed loess sample according to claim 1 or 2, characterized in that, In step 3), the height of the bottom operation area (6) is 0.4 - 0.5 m.

7. The sampling method of a large-size undisturbed loess sample as described in claim 5, characterized in that In step 3), the height of the bottom operation area (6) is 0.4 - 0.5 m.

8. The sampling method of a large-sized undisturbed loess sample according to claim 1 or 2, characterized in that, The top of the pallet base (8) is a plane, and the bottom is provided with a plurality of downwardly protruding bosses; the temporary support (9) is in a trapezoidal structure and is connected to the bottom bosses of the pallet base (8) to support the sample (4), and a framework gap is formed between the bottom of the pallet base (8) and the temporary support (9).

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