JPH0431531Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field: Concerning the improvement of a strain meter for measuring strain in soil.

(b) Conventional technology Conventionally, a borehole of this kind was excavated to the depth of the soil to be measured, a strain gauge was placed at the bottom of the borehole, and the strain was measured by filling the hole back into the ground and measuring the strain in the surrounding soil. ing.

(c) Problems to be solved by the invention In the conventional measurement described above, the inner wall of the borehole in the area around where the strain gauge was installed is already in a state where the stress is released, and the backfilled soil By being surrounded, measurements are taken on conditions that are already quite different from the original ground. For this reason, there was a problem in that the measured data contained many errors.

(d) Means for solving the problem: a base; at least a pair of strain levers protruding from the base in the same direction and having a predetermined interval;
It consists of a storage case which has one end fixed to the base and stores both strain levers with only their tips exposed, and strain gauges attached to both levers.

(E) Action First, insert the tips of both strain levers into the ground.
When strain occurs in the surrounding ground, both strain levers are displaced and deformed accordingly. Then, the strain gauges attached to both strain levers sense this electrically. This electrical output is taken out by an indicator at a predetermined location.

(f) Embodiment An embodiment of this invention will be described below with reference to the drawings. Reference numeral 1 denotes a base formed by forming four arms 2 to 5 in the shape of a square bar made of metal, for example, into a cross shape. At both end members of the arms 2 and 3, long plate-shaped strain levers 6 and 7 made of a flexible material with low bending rigidity, such as synthetic resin, are arranged with one side facing each other in order to follow the movement of the soil. , and protrude in the same direction. Similarly, strain levers 8 and 9 are protruded from both ends of the arms 4 and 5. Passive parts 10-13 are formed at the tip of each strain lever 6-9. Further, the strain levers 6 to 9 are connected to storage cases 14 to 17 whose ends are fixed to the arms 2 to 5.
Only the passive parts 10 to 13 are left and housed. Each of the storage cases 14 to 17 is made of, for example, synthetic resin, and is formed with a space surrounding each of the strain levers 6 to 9. The other end opening of each of these storage cases 14-17 is closed by covers 18-21 made of, for example, a thin rubber plate material. Strain gauges 22 to 29 are attached to both sides of the fixed side portion of each strain lever 6 to 9, respectively, and the strain gauges 22 to 25 attached to the pair of strain levers 6 and 7 are connected to The bridge circuit shown in FIG.
29 constitutes a bridge circuit shown in FIG. Further, a pipe attachment portion 31 is formed in the center of the base portion 1, into which the operation pipe 30 is removably screwed in a direction opposite to the protruding direction of the strain levers 6 to 9. Further, each arm 2 to 5 has a through hole 32 extending from the pipe attachment part 31 toward each tip end side.
... is formed, and each strain gauge 22 to 29
is led out through this through hole 32 by a cable 33 and connected to an indicator 34. The cable 33 exiting through the through holes 32 is protected and housed in a soft protective tube 35. This protective tube 35 can be passed through the operating pipe 30 and used.

Next, its usage will be explained. First, a bore hole 36 is excavated to the ground depth to be measured.
On the other hand, the cable 33 stored in the protective tube 35
is passed through the operating pipe 30, and one end of the operating pipe 30 is screwed into the pipe attachment part 31. After doing this, the operation pipe 30 is inserted into the borehole 36 with the one end side first. Then, each of the strain levers 6 to 9 is inserted into the bottom surface of the boring hole 36 so as to be located on the measurement line. Thereafter, the operating pipe 30 is rotated on the ground, removed from the pipe attachment part 31, and pulled up. Furthermore, the borehole 36 is refilled and the end of the cable 33 is connected to the indicator 3.
Connect to 4. Once the setting is completed in this way, measurements can be carried out subsequently. That is,
Suppose that the ground is strained in the direction indicated by line A in Figure 4, for example, on the compression side. Then, the passive parts 10 and 11 are displaced in a direction that reduces the distance between them (as shown by the two-dot chain line in FIG. 3 as an example), and the strain levers 6 and 7 are bent (at this time, the covers 18 and 19 are (Since the strain gauges 22 to 25 are formed by the strain levers 6 and 7, they deform and follow the movement of the strain levers 6 and 7, so the movement of the strain levers 6 and 7 is not restricted in any way). bring about change. Therefore, by generating an output voltage from the bridge circuit shown in FIG. 5 and measuring this with the indicator 34 via the cable 33, the amount of displacement between the passive parts 10 and 11 can be obtained. Similarly, if strain occurs in the ground in the direction shown by line B in Figure 4, the passive parts 12 and 13 will be displaced, and the amount of displacement between the passive parts 12 and 13 can be obtained by measuring with the indicator 34. can.

If the amount of displacement in the direction shown by line A in Figure 4 obtained here is Δl, the distance between the strain levers 6 and 7 (the distance between the passive parts 10 and 11) is l, and the strain of the soil is ε, then ε=Δl/ The strain in the soil can be calculated using l, and the direction of line B can also be calculated using the same formula.

In the above embodiment, two pairs of strain levers are provided, but when measuring strain in one direction, a pair of strain levers may be used. Further, according to this invention, measurements near the ground surface can be carried out without digging a borehole or the like, and in this case, there is no need for an operating pipe or the like as in the above embodiment. Furthermore, depending on the degree of softness of the ground, it is also possible to make the lower surface of the base tapered to reduce penetration resistance and penetrate to a predetermined depth without drilling a borehole. It goes without saying that the storage case may be made of a material that flexes slightly in response to the strain of the soil.

(g) Effects of the invention: Installation can be done by simply inserting the tip of the strain lever, and therefore measurements can be made without destroying the tissue, such as by excavating the ground to be measured, and highly reliable data can be obtained. be able to. This method is especially suitable for soft ground because the amount of strain in the soil is large and destruction of the soil structure is disliked. Furthermore, since the structure is relatively simple, manufacturing costs can be reduced and other excellent effects can be achieved.

[Brief explanation of the drawing]

The drawings show one embodiment of this invention, and FIG. 1 is a perspective view, FIG. 2 is an explanatory diagram of the installed state, FIG. 3 is a vertical sectional view, FIG. 4 is a horizontal sectional view, and FIGS. 5 and 6. The figure is a bridge circuit diagram. 1...Base, 6-9...Strain lever, 14-1
7...Storage case, 22-29...Strain gauge.

Claims (1)

[Scope of utility model registration request] a base; at least a pair of strain levers protruding from the base in the same direction and having a predetermined interval;
A strain gauge characterized by comprising a storage case having one end fixed to a base and housing both strain levers with only their tips exposed, and strain gauges affixed to both levers.