Dry-wet cycle device for coarse-grained soil medium-sized shear apparatus sample

Abstract

The invention provides a dry-wet circulation device for a coarse-grained soil medium-sized shear apparatus sample, which comprises: a dry-wet circulation box, the dry-wet circulation box comprises a box body and a processing chamber arranged in the box body, and the processing chamber is internally provided with an automatic turntable and an electronic balance; the dry-wet cycle sample preparation box comprises a first box body and a second box body, the first box body and the second box body are in butt joint and fixed to form a coarse-grained soil sample forming area, the dry-wet cycle sample preparation box is placed on an electronic balance after being filled with samples, and a dispersion pipe used for supplementing water is further arranged in the dry-wet cycle sample preparation box; and the heating system comprises a heating unit and a detection unit inserted into the sample. According to the dry-wet cycle sample preparation box provided by the invention, dry-wet cycle of a coarse-grained soil medium-sized shear apparatus sample is carried out, non-uniform shrinkage of a soil body is reduced by utilizing the dispersion pipe to be matched with microwave heating, the condition of inconsistent internal and external drying effects is avoided, and the sample treatment effect is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coarse-grained soil specimen treatment, and particularly relates to a dry-wet cycling device for specimens of medium-sized shear testers for coarse-grained soil. Background Art

[0002] The climate change with alternating rainfall and drought will cause the dry-wet cycling effect on soil. Long-term dry-wet cycling will cause changes in the composition, physical structure and mechanical properties of the soil. Researchers believe that dry-wet cycling will cause the deterioration of coarse-grained soil. With the increase in the number of dry-wet cycles, the dry-wet cycling effect intensifies the particle breakage of coarse-grained soil, and the strength and its characteristic parameters of coarse-grained soil gradually decrease with the increase in the number of dry-wet cycles. The strength and deformation of coarse-grained soil under dry-wet cycling have high research value, and studying this process is of great significance for the mechanical properties of coarse-grained soil and the prevention and control of landslide disasters.

[0003] At present, for the shear test of coarse-grained soil under dry-wet cycling conditions, due to the large particle size of coarse-grained soil, large and medium-sized test equipment is required for the test. There are many deficiencies in the dry-wet cycling devices supporting large and medium-sized coarse-grained soil shear tests, and it is difficult to realize the dry-wet cycling process under real conditions. The method of low-temperature drying in an oven is not applicable to large and medium-sized specimens. Due to the size problem of large and medium-sized specimens, the drying effect inside and outside the specimens will be different, and uneven shrinkage will also occur. And using high-temperature drying will exacerbate the shrinkage of the soil, which is not conducive to re-saturation, resulting in poor treatment effect of the final large specimens. Summary of the Invention

[0004] The present invention provides a dry-wet cycling device for specimens of medium-sized shear testers for coarse-grained soil, aiming to solve the problems that the equipment is prone to soil shrinkage and different drying effects inside and outside when processing large and medium-sized specimens, which affect the treatment effect of the specimens.

[0005] The present invention is implemented as follows. A dry-wet cycling device for specimens of medium-sized shear testers for coarse-grained soil includes:

[0006] A dry-wet cycling box, which includes a box body with a door and a treatment chamber arranged inside the box body. An automatic turntable and an electronic balance for recording the change of weight data are arranged inside the treatment chamber;

[0007] A dry-wet cycling sample preparation box, which includes a first box body and a second box body. The first box body and the second box body are butt-jointed and fixed to form a forming area for coarse-grained soil specimens. After the dry-wet cycling sample preparation box is filled with specimens, it is placed on the electronic balance. A dispersion pipe for water replenishment is also arranged inside the dry-wet cycling sample preparation box;

[0008] A heating system, the heating system includes a heating unit and a detection unit, the detection unit is inserted into the interior of a wet-dry cycling sample preparation box to be heated, and the heating unit is arranged on one side of the wet-dry cycling sample preparation box.

[0009] Preferably, the inner walls of the first box body and the second box body are provided with grooves for arranging dispersion tubes, and the grooves are arranged in a spiral manner on the circumferential side of the coarse-grained soil sample forming area. When water injection is required, the dispersion tubes supply water to the samples in the coarse-grained soil sample forming area.

[0010] Preferably, the dispersion tubes are arranged in the grooves of the spiral structure after being arranged, and several groups of holes are provided on the end faces of the dispersion tubes facing the coarse-grained soil sample forming area, and permeable stones are provided at the holes.

[0011] Preferably, the heating unit includes a boosting circuit, a magnetron and a temperature controller. The temperature controller is electrically connected to the detection unit, and the boosting circuit controls the magnetron to perform microwave heating with the help of the temperature controller.

[0012] Preferably, the detection unit includes a probe type temperature sensor and a fixing bracket. The fixing bracket is suspended above the electronic balance, one end of the probe type temperature sensor is arranged on the fixing bracket, and the other end is inserted into the wet-dry cycling sample preparation box placed on the electronic balance.

[0013] Preferably, both the first box body and the second box body are open cuboid structures on two sides. After the first box body and the second box body are butted against each other, a cuboid structure with an open top is formed. The end faces where the first box body and the second box body are connected are tenon and mortise structures, and the first box body and the second box body are connected by a buckle.

[0014] Preferably, the wet-dry cycling device for the coarse-grained soil medium shear test sample further includes a water replenisher. The water replenisher is arranged outside the wet-dry cycling box. During the water replenishing process, the water replenisher is communicated with the dispersion tubes through pipelines. After the water replenishing operation is completed, the connecting pipeline between the water replenisher and the dispersion tubes is removed from the dispersion tubes.

[0015] Preferably, a cushion rod is further provided on the bearing surface of the electronic balance, and the wet-dry cycling sample preparation box is placed on the cushion rod.

[0016] Preferably, a drain port is provided at the end of the dispersion tube. When the dispersion tube is performing the water replenishing operation, the drain port is closed. When the water replenishing operation is completed, the drain port is opened to drain the remaining liquid water in the dispersion tube.

[0017] The working process of the wet-dry cycling device for the coarse-grained soil medium shear test sample is as follows:

[0018] Step 1: Weigh the soil required for each particle size range according to the test plan, and then add water to the weighed soil sample and mix it evenly. Connect the dry-wet cycle shear sample box through the mortise and tenon structure, align the lock buckle, lock the lock buckle with a bolt, and insert the dispersion tube into the groove of the dry-wet cycle shear sample box; seal the joints of the dry-wet cycle shear sample box with waterproof tape.

[0019] Step 2: Compact the mixed coarse-grained soil in five layers in the dry-wet cycle shear sample box until the specified height is reached. After each layer is loaded, use a compacting hammer to hammer each layer of soil sample the same number of times. After each layer is compacted, loosen the surface of the layer so that it can fit well with the next layer of soil. This can minimize the influence of anisotropy. After the top layer of soil is compacted, the surface must be flat to ensure that there is no obvious coarse grain protrusion, avoid bias under normal load, and reduce test errors.

[0020] Step 3, put the electronic balance in the box, then put the pad on the electronic balance, put the dry-wet cycle sample preparation box on the pad, and add enough water to the water replenisher; the water replenisher supplies water to the dispersion tube, and records the weight of the electronic balance at this time. As the water injection proceeds, the dry-wet cycle sample preparation box stops injecting water when it reaches the weight corresponding to the target moisture content, and the water in the dispersion tube is discharged. In this process, the control valve is closed by the control mainboard according to the data sent back by the electronic balance, and the drainage of the dispersion tube is manually opened here;

[0021] Step 4. Fix the probe temperature sensor with a fixed bracket, insert the probe temperature sensor into the soil, set the target temperature of the temperature controller, control the start and stop of the magnetron to control the temperature inside the soil, turn on the magnetron and the automatic turntable to heat the soil until the dry-wet cycle sample box reaches the weight corresponding to the target moisture content.

[0022] Step 5: Cycle saturation and heating process until the test requirements are met to complete the preparation of dry-wet cycle specimens.

[0023] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0024] 1. The dry-wet cycle device for medium-sized shear tester samples of coarse-grained soil provided by the present invention performs dry-wet cycles in a dry-wet cycle sample preparation box, utilizes microwave heating to reduce uneven shrinkage of the soil, improves the uniformity of drying inside and outside the sample, and enhances the effect of sample pretreatment.

[0025] 2. The dry-wet cycle device for medium-sized shear tester samples of coarse-grained soil provided by the present invention uses a dry-wet cycle sample preparation box as a dispersion tube carrier, and utilizes the dispersion tube surrounding the sample to uniformly inject water into the coarse-grained soil sample, thereby achieving efficient water absorption of the soil and improving the uniformity of the moisture content of the coarse-grained soil sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of a dry-wet cycling device for medium-sized shear test specimens of coarse-grained soil provided by the present invention.

[0027] Figure 2 It is a schematic structural diagram of a heating system of a dry-wet cycling device for medium-sized shear test specimens of coarse-grained soil provided by the present invention.

[0028] Figure 3 It is a schematic structural diagram of a water inlet system of a dry-wet cycling device for medium-sized shear test specimens of coarse-grained soil provided by the present invention.

[0029] Figure 4 It is a schematic structural diagram of a dispersion tube of a dry-wet cycling device for medium-sized shear test specimens of coarse-grained soil provided by the present invention.

[0030] Description of reference numerals:

[0031] 1 - Dry-wet cycling box, 11 - Box body, 12 - Automatic turntable, 13 - Electronic balance, 14 - Pad rod, 2 - Dry-wet cycling sample preparation box, 3 - Water inlet system, 31 - Dispersion tube, 32 - Water replenisher, 4 - Heating system, 41 - Boosting circuit, 42 - Magnetron, 43 - Probe type temperature sensor, 44 - Fixed bracket, 45 - Temperature controller. Detailed implementation manners

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification and claims of this application or the above drawings are used to distinguish different objects and not to describe a specific order.

[0033] Referring to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0034] An embodiment of the present invention provides a dry-wet cycling device for medium-sized shear test specimens of coarse-grained soil, as Figures 1 - 4As shown in the figure, the dry-wet cycling device for medium shear test specimens of coarse-grained soil includes: a dry-wet cycling box 1, a dry-wet cycling sample preparation box 2, a water inlet system 3, and a heating system 4;

[0035] The dry-wet cycling process of the specimen is realized inside the dry-wet cycling box 1, and the dry-wet cycling sample preparation box 2 is placed inside the dry-wet cycling box 1. The water inlet system 3 evenly injects water into the dry-wet cycling sample preparation box 2 through a dispersion pipe to achieve dry-wet cycling. The heating system 4 heats the specimen by microwave heating, and the specimen does not need to be frequently moved during the dry-wet cycling process, thus reducing the interference degree to the coarse-grained soil specimen;

[0036] The dry-wet cycling box 1 includes a box body 11 made of metal material, an automatic turntable 12, an electronic balance 13, and a cushion rod 14. The interior of the box body 11 is hollow to place the dry-wet cycling sample preparation box 2 for loading dry-wet cycling specimens. The hollow area inside the box body 11 is a processing chamber. The automatic turntable 12, the electronic balance 13, and the cushion rod 14 arranged on the electronic balance 13 are placed in the processing chamber from low to high in sequence. The electronic balance 13 is used to monitor the weight change of the specimen during the dry-wet cycling process, and the automatic turntable 12 is used to drive the dry-wet cycling sample preparation box 2 to rotate, making the heating by the heating system 4 more uniform and improving the temperature stability inside the dry-wet cycling sample preparation box 2;

[0037] The dry-wet cycling sample preparation box 2 is placed on the cushion rod 14 for weighing, and the cushion rod 14 makes it easier to take out the sample preparation box from the box body. Since the heating system 4 includes a heating unit and a detection unit, the heating unit is set on one side of the processing chamber by using microwave heating technology, and the box body 11 made of metal material can block microwaves to prevent harm to the human body;

[0038] The dry-wet cycling sample preparation box 2 includes a first box body and a second box body, both of which are open cuboid structures on two sides. After the first box body and the second box body are butted against each other, a cuboid structure with open top and bottom is formed. The first box body and the second box body are butted and fixed to form a forming area for the coarse-grained soil specimen. The dry-wet cycling sample preparation box 2 is detachably connected by a mortise and tenon structure. There are locking catches on the left and right sides of the dry-wet cycling sample preparation box 2, and the locking catches are fixed by bolts. The structure is simple and convenient for disassembly, avoiding damage to the specimen during the demolding process; the dry-wet cycling sample preparation box 2 is placed on the electronic balance 13 after loading the specimen,

[0039] As a preferred implementation manner in this embodiment, the heating unit includes a boost circuit 41, a magnetron 42, and a temperature controller 45. The temperature controller 45 is electrically connected to the detection unit. The boost circuit 41 controls the magnetron 42 to perform microwave heating with the help of the temperature controller 45. The detection unit includes a probe-type temperature sensor 43 and a fixed bracket 44. The fixed bracket 44 is suspended above the electronic balance 13. One end of the probe-type temperature sensor 43 is arranged on the fixed bracket, and the other end is inserted into the inside of the wet-dry cycling sample preparation box 2 placed on the electronic balance 13.

[0040] In this embodiment, the boost circuit 41 provides the high-voltage direct current required by the magnetron 42. The magnetron 42 emits microwaves to heat the sample. This heating method is fast and uniform, and also has multiple advantages such as energy saving, high efficiency, cleanliness, and environmental protection. The probe-type temperature sensor 43 is fixed above the sample through the fixed bracket 44 to monitor the internal temperature of the sample. The temperature controller 45 controls the start and stop of the magnetron 42 through the internal temperature of the sample, which can keep the soil at a lower temperature, avoid excessive shrinkage of the soil caused by too high a temperature of the soil due to microwave heating, and reduce the problem of cracks caused by uneven shrinkage.

[0041] As a preferred implementation manner in this embodiment, the water inlet system 3 includes a dispersion pipe 31 and a water replenisher 32. The dispersion pipe 31 for water replenishment is arranged inside the wet-dry cycling sample preparation box 2. One end of the dispersion pipe 31 is the liquid inlet end, and the other end is the liquid discharge end. The inner walls of the first box body and the second box body are provided with grooves for arranging the dispersion pipe (31). The grooves are arranged in a spiral manner on the circumferential side of the coarse-grained soil sample forming area, extend downward from the side of the liquid inlet end around and inlaid on the inner wall of the wet-dry cycling sample preparation box 2. The dispersion pipe 31 finally winds around the outside of the sample to uniformly inject water into the coarse-grained soil sample to uniformly increase its moisture content. The body of the dispersion pipe 31 is evenly distributed with holes, and the holes are sealed with permeable stones to prevent soil from entering the inside of the dispersion pipe during the seepage process.

[0042] In this embodiment, the water replenisher 32 is arranged outside the wet-dry cycling box 1, and the water replenisher 32 adopts an existing automatic water replenishing bucket; the water replenisher 32 is communicated with the liquid inlet end of the dispersion pipe 31 through a pipeline. When the water seepage operation is carried out, the drain port provided at the liquid discharge end of the dispersion pipe 31 is closed by a plug. When the water seepage operation reaches a certain degree, the water replenisher 32 stops injecting water into the dispersion pipe 31, and at the same time, the drain port on the dispersion pipe 31 is opened to quickly drain the water inside the pipeline; during the water replenishing process, the water replenisher 32 is communicated with the dispersion pipe 31 through a pipeline. After the water replenishing operation is completed, the connecting pipeline between the water replenisher 32 and the dispersion pipe 31 is removed from the dispersion pipe 31. The water replenishing operation and the heating process are carried out at intervals. When the water replenishing operation is carried out, the connecting pipeline between the water replenisher 32 and the dispersion pipe 31 can be communicated under the condition that the door body of the box body 11 is opened, and the pipeline enters the interior of the box body 11 from the front of the opened box body;

[0043] The working process of the wet-dry cycling device for medium shear test specimens of coarse-grained soil is as follows:

[0044] Step 1: Weigh the soil required for each particle size range according to the test plan, and then add water to the weighed soil samples and mix them evenly. Connect the wet-dry cycling shear sample preparation box 2 through a mortise and tenon structure, align the lock catches, and lock the lock catches with bolts. Embed the dispersion pipe 31 into the groove of the wet-dry cycling shear sample preparation box 2. Seal the joints of the wet-dry cycling shear sample preparation box 2 with waterproof tape.

[0045] Step 2: Gradually compact the mixed coarse-grained soil in the wet-dry cycling shear sample preparation box 2 in five layers until the specified height is reached. After each layer of soil is filled, use a compaction hammer to hammer the soil samples of each layer the same number of times. After each layer is compacted, loosen the surface of the layer to facilitate good embedding with the next layer of soil, which can minimize the influence of anisotropy as much as possible. After the top layer of soil is compacted, it is necessary to ensure that the surface is flat and there are no obvious coarse grains protruding to avoid the phenomenon of eccentric pressure under the action of the normal load and reduce the test error.

[0046] Step 3: Place an electronic balance 13 in the box body 11, and then place a cushion rod 14 on the electronic balance 13. Place the wet-dry cycling sample preparation box 2 on the cushion rod 14. Add sufficient water to the water replenisher 32. The water replenisher 32 supplies water to the dispersion pipe 31, and record the weight of the electronic balance 13 at this time. As the water injection progresses, stop the water injection when the wet-dry cycling sample preparation box reaches the weight corresponding to the target moisture content, and drain the water in the dispersion pipe 31. This process closes the control valve by the control main board according to the data transmitted back by the electronic balance 13. Here, the liquid discharge of the dispersion pipe 31 adopts a manual opening method;

[0047] A liquid supply pipeline and a liquid discharge pipeline are arranged on the box body 11 described herein. The liquid supply pipe and the liquid discharge pipe penetrate through the box body 11. The part of the liquid discharge pipe inside the box body 11 is connected to the liquid discharge end of the dispersion pipe 31. A blockage is provided at the outlet of the liquid discharge pipeline outside the box body 11, and liquid can be manually discharged. The part of the liquid supply pipeline inside the box body 11 is connected to the liquid inlet end of the dispersion pipe 31, and one end of the liquid supply pipe outside the box body 11 is communicated with the water replenisher 32; a control valve is arranged on the liquid supply pipe;

[0048] Step Four: Fix the probe-type temperature sensor 43 with the fixing bracket 44. Insert the probe-type temperature sensor 43 into the soil body. Set the target temperature of the temperature controller 45, and control the start and stop of the magnetron 42 to control the temperature inside the soil body. Turn on the magnetron 42 and the automatic turntable 12 to heat the soil body until the weight of the wet-dry cycle sample preparation box reaches the weight corresponding to the target moisture content.

[0049] Step Five: Cycle the saturation and heating processes until the test requirements are met, and complete the preparation of the wet-dry cycle sample.

[0050] It should be noted that for the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps may be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the protection scope of the invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still, without conflict, make combinations, additions, deletions, or other adjustments to the features in the embodiments of the present invention according to the situation without creative efforts, so as to obtain different technical solutions that are essentially not divorced from the concept of the present invention, and these technical solutions also belong to the scope of protection of the present invention.

Claims

1. A dry-wet cycle device for medium-sized shear tester specimens of coarse-grained soil, characterized in that: include: A dry-wet cycle box (1), comprising a box body (11) with a door body and a processing chamber arranged inside the box body (11), wherein the processing chamber is provided with an automatic turntable (12) and an electronic balance (13) arranged on the automatic turntable (12) for recording weight data changes; A dry-wet cycle sample preparation box (2), the dry-wet cycle sample preparation box (2) comprising a first box body and a second box body, the first box body and the second box body being butted and fixed to form a coarse-grained soil sample forming area, the dry-wet cycle sample preparation box (2) being placed on an electronic balance (13) after the sample is filled, and a dispersion pipe (31) for water replenishment is also arranged inside the dry-wet cycle sample preparation box (2); A heating system (4), the heating system (4) comprising a heating unit and a detection unit, the detection unit being inserted into a dry-wet cycle sample preparation box (2) to be heated, and the heating unit being arranged on one side of the dry-wet cycle sample preparation box (2).

2. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 1, characterized in that: The inner walls of the first box body and the second box body are provided with grooves for arranging a dispersion pipe (31), the grooves being arranged in a spiral manner on the annular side of the coarse-grained soil sample forming area, and when water injection is required, the dispersion pipe (31) is used to replenish water to the sample in the coarse-grained soil sample forming area.

3. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 2, characterized in that: The dispersion tubes (31) are arranged in a groove of a spiral structure, and the end surface of the dispersion tubes (31) facing the coarse-grained soil sample forming area is provided with a plurality of groups of holes.

4. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as described in claim 2, wherein permeable stones are provided at the holes.

5. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 4, characterized in that: The heating unit comprises a boost circuit (41), a magnetron (42) and a temperature controller (45); the temperature controller (45) is electrically connected to the detection unit; and the boost circuit (41) controls the magnetron (42) to perform microwave heating with the help of the temperature controller (45).

6. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 5, characterized in that: The detection unit comprises a probe-type temperature sensor (43) and a fixed bracket (44), wherein the fixed bracket (44) is suspended above the electronic balance (13), and one end of the probe-type temperature sensor (43) is arranged on the fixed bracket, and the other end is inserted into a dry-wet cycle sample preparation box (2) placed on the electronic balance (13).

7. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 6, characterized in that: The first box body and the second box body are both rectangular structures with open sides. When the first box body and the second box body are connected to each other, a rectangular structure with an open top is formed. The end surface where the first box body and the second box body are connected is a mortise and tenon structure, and the first box body and the second box body are connected by a lock.

8. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 1, characterized in that: The dry-wet cycle device for coarse-grained soil medium-sized shear tester specimens further comprises a water replenisher (32), wherein the water replenisher (32) is arranged outside the dry-wet cycle box (1), and during the water replenishment process, the water replenisher (32) is connected to the dispersion pipe (31) through a pipeline, and after the water replenishment operation is completed, the connecting pipeline between the water replenisher (32) and the dispersion pipe (31) is removed from the dispersion pipe (31).

9. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 8, characterized in that: A drain outlet is provided at the end of the dispersion pipe (31). When the dispersion pipe (31) is undergoing a water replenishment operation, the drain outlet is closed. When the water replenishment operation is completed, the drain outlet is opened to discharge the remaining liquid water in the dispersion pipe (31).

10. A dry-wet cycle device for a medium-sized shear tester sample of coarse-grained soil as claimed in claim 1, characterized in that: The load-bearing surface of the electronic balance (13) is also provided with a pad rod (14), and the dry-wet cycle sample preparation box (2) is placed on the pad rod (14).

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