JP2691583B2 - Ground strength determination device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ground strength judging device, and more particularly to a ground strength judging device suitable for judging ground strength in a low strength range such as a residential area. is there.

[Conventional technology]

The flat plate loading test is a kind of in-situ test method that examines the soil quality under the ground surface at a construction site without taking samples, and calculates the ground coefficient from the relationship between the load and the subsidence of the ground to determine the bearing capacity. This is a test for calculating. This test method is JIS-A121
As specified in 5. An outline of an example of the test apparatus is shown in FIG.

In the conventional example shown in FIG. 8, first, the test ground 51 corresponding to the actual bottom surface of the ground is obtained by removing the surface layer of the ground surface.
Level horizontally. A loading plate 52 is placed on the foundation ground 51, and a jack 54 equipped with a pressure gauge 53 is placed thereon. Loading plate 52
A circle with a diameter of 30 cm or a square with a width of 30 cm is usually used. A load support beam 55 that receives a reaction force from the jack 54 is placed on the jack 54. The load-bearing beam 55 is made of a material that has high rigidity and does not easily bend, and the weight supporting beam 55 is designed to withstand the jerk reaction force.
Mount 56 and fix it firmly so that it does not move. A dial gauge 57 is arranged between the load supporting beam 55 and the loading plate 52.

The test device having the above configuration is assembled at the construction site every time, and thereafter, the load test is performed.

Next, the outline of the test method in this conventional example will be briefly described.

After setting the test equipment, while watching the pressure gauge 53, a load of a predetermined magnitude is always applied, and the jack 54 is adjusted to act on the load supporting beam 55, and the reaction force gives a load to the test ground 51. . The subsidence amount of the test ground 51 at this time (a value when the subsidence can be considered to have stopped) is read by the dial gauge 57, and the "load-subsidence amount" relationship is plotted in a graph. With this procedure, a "load-sink curve" is created by carrying out loads of various sizes.

Based on the shape of this curve, it is determined whether the ground has a general shear failure or the ground has a local shear failure. At the same time, the bearing capacity obtained from this curve is used to determine the bearing capacity for the actual foundation by making further corrections in consideration of the effects of various on-site conditions (eg construction conditions, size of structure, etc.). .

[Problems to be solved by the invention]

However, in the above-mentioned conventional example, when the entire apparatus is operated, large equipment and heavy objects such as the load supporting beam 55 and the weight 56 are required, and because of the complicated installation on site, the ground strength is reduced. There is an inconvenience that skill is required for the determination.

On the other hand, since it is rarely used in a large residential area or the like where measurement at a plurality of points is required, in many cases a structure is constructed without grasping the characteristics of the ground at the site. Therefore, there is a disadvantage that a partial subsidence accident or the like is likely to occur at a later date.

[Object of the invention]

An object of the present invention is to improve the inconvenience of the conventional example, to provide a ground strength judging device which can easily judge the ground strength of a residential area or the like at a large number of points and which is easy to handle.

[Means for solving the problem]

In order to achieve the above object, in the present invention, a circular or square flat loading plate, a load loading unit with a load meter vertically installed on the center of the upper surface of the loading plate, and the load loading unit The loading plate fixing means arranged above and the measuring means for measuring the sinking amount of the above-mentioned loading plate are provided.

Further, the above-mentioned loading plate is made detachable with respect to the load loading means, and the load loading means is used to adjust the load loading step and the magnitude of the load applied from the step part toward the loading plate described above. It consists of a load cell to be displayed.

Then, the above-mentioned measuring means is arranged in the vicinity of the load-carrying means, and the load-carrying means is equipped with a probe for transmitting information concerning the sinking amount of the loading plate to the measuring means. .

[Action]

Insert a loading plate with a bottom area corresponding to the required load strength at the bottom end of the device, place a foot on the platform by the measurer, and while watching the load meter, keep the weight until the required load strength is obtained. Move on. At that time, in order that the load is evenly applied to the ground through the loading plate, the whole device is always vertical, while the measurer supports the whole by the fixing means, and at the same time supports the measurer's own body so that it does not wobble. Then, the subsidence amount at that time is read from the measuring means, and the value is taken as the subsidence amount with respect to the loaded load.

In this procedure, the "load-sink curve" is obtained by continuously measuring the different load strengths and recording the results.

First Embodiment of the Invention Hereinafter, a first embodiment of the present invention will be described with reference to FIG.

 The present invention is roughly divided into two parts.

One is a load loading section for loading a load on the test ground 1, and the other is a measuring section for measuring the subsidence amount of the test ground 1.

 First, the load carrying section will be described with reference to FIG.

The loading plate 2 which directly contacts the test ground 1 and loads the load,
It is arranged at the lowermost end of the load carrying section. This loading plate 2
Is a circular plate with a very flat top and bottom, and has a diameter of 3.
6 [cm] (10 cm ² , 5.0 [cm] (20 cm ² ), 6.2 [cm] (30c
m ² ), 8 [cm] (50 cm ² ) is prepared and has a structure that can be easily replaced. On the center of the upper surface of the loading plate 2, a load converter 4 which is a part of load loading means including a load meter 3 capable of knowing the magnitude of the load acting on the loading plate 2 is vertically erected. It is set up. Inside the load converter 4, a coil spring (not shown)
Alternatively, an equipment such as an oil cylinder (not shown) is equipped, and the load strength can be read by a load meter according to the amount of contraction.

Further, above the load converter 4, there are two sides facing the step 5 which is a part of a load-carrying means in the shape of a strong rectangular frame for placing one foot when the measurer loads the weight as a load. Is placed vertically, and the other two sides of the upper and lower sides are arranged horizontally.

In this step 5, the measurer puts one foot on the test ground 1,
It is arranged at a position not too high so that the other one foot is not unstable when it is hung on the pedestal 5 and the weight can be sufficiently loaded. At the center of the upper side of the step 5, a pipe-shaped rod 6 as a fixing means is vertically provided coaxially with the loading plate 2, the load converter 4, and the step 5. Rod 6
A handle 7 is horizontally arranged and fixed to the uppermost part of the rod 6 at right angles to the rod 6. This handle 7 prevents the measurer from becoming unstable when the measurer puts one foot on the step 5 and puts his weight on it, and keeps the vertical position when the device sinks. It is provided to support so that

That is, the rod 6 and the handle 7 constitute a loading plate fixing means.

Next, the measuring unit will be described with reference to FIG.

A reference stand 8 is horizontally fixed on the test ground 1 and serves as a reference for the height of the test ground 1. One or a plurality of protrusions 8a that serve as simple anchors are provided on the lower surface.
Further, a strong arm 8b is horizontally projected at the same height as the upper surface, and a sinkage measuring dial gauge 9 is placed on it and fixed by a magnet base. Dial gauge 9 probe
Reference numeral 10 is in close contact with the subsidence amount measuring arm 11 that is provided so as to project from the load converter 4. That is, this measuring unit is shown in FIG.
As shown in, it is installed on the ground near the load converter 4.

 Next, the operation of the present invention will be described.

The main body loading part assembled in the vicinity of the measurement site and equipped with a loading plate 2 of a predetermined size (a loading plate having a diameter of 5 cm is standard) is gently installed vertically near the measurement point of the test ground 1. The loading plate 2 is in horizontal contact with the test ground 1 so that the load is uniformly loaded.

On the test ground 1, the reference base 8 is horizontally fixed near the installed main body loading portion, and the subsidence measurement dial gauge 9 is set between the reference base 8 and the subsidence measurement arm 11, and the dial is set. The gauge head 10 is brought into close contact with the arm 11, and the dial gauge 9 is set to zero.

Next, the measurer puts one foot on the step 5 so that a predetermined load strength can be continuously obtained, adjusts the weight while watching the load meter, reads the dial gauge 9, and measures the ground strength against the load strength at that time. The amount of subsidence. Procedure for load loading and sinking amount measurement Change the load size at the same measurement point 1
Do the point or several points to obtain the relationship of [load-sink amount].

Next, a method of using or analyzing the measurement results thus obtained will be described.

The bearing capacity for the residential area targeted by this device is 5
It is about [t / m ² ]. Therefore, considering the safety factor as "3", it is sufficient to measure about 15 [t / m ² ]. Therefore, it is considered that the measurer can apply 50 [kg] of his / her weight as a load, and 15 [tm ² ] (= 1.
5 [kg / cm ² ]) In order to load a load equivalent to, the required bottom area A of the loading plate is (50 / A) ≧ 1.5, so A ≦ (50 / 1.5) = 33.33 [cm ² ] Therefore, It can be seen that the ground in a residential area can be measured sufficiently if the diameter is 6.5 cm or less.

Thus, when measuring the ground of a residential area, it is sufficient to insert a loading plate having a diameter of 6 cm into the device and perform the test.

Next, the method of analyzing the values measured using this device will be described. It is roughly divided and used for two kinds of analysis.

[First analysis] Terzaghi's ultimate bearing capacity is required for cohesive soils with an internal friction angle of 12 ° or less, such as viscosity, loam, etc., except for sandy rivers, coasts, or sandy soils. It can be said that the formula is independent of the size of the loading plate.

On the other hand, there are many unclear points regarding the behavior of soil, and various behaviors are exhibited under various conditions. Now, when it comes to destruction patterns, they are roughly divided into the following two patterns.
1) General destruction, 2) Local destruction. The characteristics of these two fracture patterns can be explained by the curve of "load strength-sink amount" shown in FIG.

The general failure of 1) exhibits the behavior shown by the curve (a) in the figure. The characteristic of this curve is that as the load strength increases,
In the range where the load strength is small, the subsidence amount is almost proportional to the load strength and is close to a straight line. Then, when the load strength increases to some extent, the amount of subsidence rapidly increases from a certain point, and thereafter, only the amount of subsidence increases without increasing the load strength.

Therefore, on the ground of this fracture pattern, a fairly clear ultimate bearing capacity ((A) in the figure) is obtained. Since this ground is generally "strong" ground and sufficient strength can be expected, it can be judged that there is no problem for a light structure such as a house.

Therefore, the curve shown in FIG. 2 (a) is, ultimate bearing capacity (A) or 15 [t / m ^2] of about (safety factor = 3, the allowable bearing capacity 5 [t / m ^2] Ground of anticipation of) If you plot the results obtained by using this judgment device by plotting the test results of the actual test, the test ground will be obtained from the relationship between that point and the curve drawn in the diagram. You can roughly evaluate the safety of.

2) can be said to be local destruction. The curve (b) in the figure shows a very general local failure, and (c) the failure of extremely soft ground.
No clear destruction is seen with either pattern. Although these patterns do not cause rapid ground destruction, the ground subsidence does not decrease forever, and after construction in a residential area, the structure tends to incline and unjustly subside, which is problematic.

In the local failure shown by the curve (b), the point at which the amount of subsidence increases sharply compared to the beginning of loading is the yield point, and half the strength can be the allowable bearing capacity. In the destruction of the curve (c), it is impossible to find a point where the amount of subsidence increases rapidly. It can be said that the ground of this pattern is extremely soft and is not suitable for installing a structure.

As described above, it is possible to determine which of the destruction patterns the ground belongs to by using the determination device of the present invention, and it can be said that the ground is good if it is close to the pattern of the curve (a). or,
If it is close to the pattern of the curve (c), it is very easy to determine that the ground is soft and unsuitable for installation of a structure.

In the case of the pattern of curve (b) in FIG. 2, the analysis described below is further performed.

[Second Analysis] For the local failure pattern of the curve (b) in the above-mentioned first analysis (this type is used for most of the ground), an approximate bearing capacity is obtained by the following method. In a normal flat plate loading test, a circular loading plate with a diameter of 30 cm is often used. As mentioned above, when the safety factor is set to "3", a load strength of approximately 15 [t / m ² ] is required, so the diameter
Even with a disc of 30 cm, a load of approximately 1 t is required, and it is not enough to load a person's weight as a load. In addition, even when loading with a weight,
Carrying a weight larger than [t] is contrary to the purpose of the present device, which is to make a judgment easily.

However, it has already been explained that a load strength of 15 [t / m ² ] can be obtained by using the weight of a person by using a circular loading plate having a diameter of 5 [cm]. However, the relationship between the "load-sink amount" obtained with a loading plate with a diameter of 5 cm and the normal diameter 30
It cannot be simply compared with the "load-sink amount" relationship obtained using a loading plate of [cm]. Suppose the sinking amount is S ₃₀ [cm] when a load strength of P ₀ [t / m ² ] is applied using a circular loading plate with a diameter of 30 [cm], and the load is when the diameter is R [cm]. Subsidence amount S when P ₀ is loaded
It is known that the relationship with _R [cm] is S _R / S ₃₀ = R / 30 (reference document “Plate loading test in Kanto loam layer”: Ministry of Construction Architectural Research Institute).

Therefore, if the settlement amount obtained in the flat plate loading test using a loading plate with a diameter of 30 cm is reduced to 1/6, the settlement amount when using a loading plate with a diameter of 5 cm will be obtained. Becomes
Therefore, before conducting a test using this device, the diameter of 30 [cm]
"Load-sink amount curve" (Fig. 3) in which the subsidence amount obtained by actually performing the test using the loading plate of Fig. 3 is reduced according to the size of various loading plates is prepared in advance. Write the measured values in the figure. When the subsidence amount is measured and plotted for a plurality of cases, a curve as shown in FIG. 3 is obtained (x mark).

If it belongs to the general failure pattern of the curve (a), a clear ultimate bearing capacity ((A) in the figure) can be obtained, so 1/3 of this point is defined as the allowable bearing capacity.

Regarding the local failure of the curve (b), if a clear straight line portion appears at the final portion of the curve, the load at the starting point of the straight line gives the ultimate bearing capacity.

When this is difficult and in the case of curve (c), the "load-settlement curve" is plotted on a logarithmic log sheet, and the breaking point is defined as the ultimate bearing capacity. Since it is expected to increase, it is necessary to set the allowable settlement amount.

FIG. 4 is a plot of the results of an actual test using this determination device on a logarithmic log paper.

[Second Embodiment] Next, a second embodiment will be described with reference to FIG.

In the second embodiment, a load receiving base 13 for loading the weight 12 as a load is used in place of the step and the load converting unit for loading the weight of the measurer in the first embodiment. In addition, instead of the handle used for supporting the weight of the measurer when supporting the weight, the wire 14 is used to hold the weight so that the determination device acts vertically.

Even if it does in this way, in addition to having the same effect as the first embodiment described above, the size of the load to be loaded can be accurately known and easily adjusted depending on the number of weights, and the load conversion part is unnecessary. Therefore, there is an advantage that the structure becomes simpler.

In each of the above-described examples, the case where the measurer reads the relationship of “load-sink amount” and plots it on the measurement sheet is illustrated, but the present invention is not necessarily limited to this. There is no particular limitation as long as there is a device capable of directly plotting with an XY plotter or recording a "load-sink amount" relationship that can be read by a data recorder.

[Third Embodiment] Next, a third embodiment will be described with reference to FIG. still,
The same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

The third embodiment is an example in which the measurement ground in the above-described first embodiment is carried out not in the ground surface but in the boring hole 20. The holes are created by a normal boring machine or hand auger. Usually 66 in bowling
[Mm] diameter for making holes, but for hand augers 100, 150, 200
[Mm] is used.

After boring, the hole bottom 21 is smoothed, slime (drilling waste) is further removed, and then a circular loading plate having a diameter of 5 cm is set on the hole bottom 21. After that, the above method is used.
Since there are no examples of performing such static tests in the depth direction on soft ground, the utility useful for measuring the strength of soft ground is great.

[Fourth Embodiment] Next, a fourth embodiment will be described with reference to FIG. Here, the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

The fourth embodiment shown in FIG. 7 is the side surface of the cut soil.
It is carried out horizontally from 30 and is useful for knowing elastic properties rather than strength.

〔The invention's effect〕

Since the present invention is configured and functions as described above, according to this, it is small in size and has good portability and operability without using a large-scale test device as in the conventional case, and moreover, it can support the ground. It is possible to provide an unprecedented excellent ground strength determination device that can be determined extremely easily.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of the present invention, FIGS. 2 to 3 are diagrams showing a load-sink amount relationship, and FIG. 4 is a result of actual measurement using the apparatus of the present invention. FIG. 5 (1) is a front view showing a second embodiment of the present invention.
5 (2) is a plan view of FIG. 5 (1), FIG. 6 is a front view showing a third embodiment of the present invention, and FIG. 7 is a side view showing a fourth embodiment of the present invention. FIG. 8 is a front view showing a conventional example. 2 ... Loading plate, 3 ... Load meter, 4 ... Load converter, which is an essential part of load loading means, 5 ... Step, 6 ... Rod, which is a part of fixing means for loading plate, 7 ... A handle (handle) that forms part of the fixing means for the loading plate, 8 ... a base that forms part of the measuring means, 9 ... a dial gauge that forms part of the measuring means, 10 ... an arm for measuring the sinking amount, 11 ... Stylus.

Claims (2)

(57) [Claims] 1. A circular or square flat plate-shaped loading plate,
A load-carrying means with a load meter vertically installed on the center of the upper surface of the load-carrying board, a means for fixing the load-carrying board arranged on the load-carrying means, and measuring the sinking amount of the aforementioned board. Measuring means is provided to make the load plate detachable from the load loading means, and the load loading means is used as a load loading step,
A load meter that displays the magnitude of the load applied from the step portion toward the packing plate described above, and the measuring means is arranged in the vicinity of the load loading means, and the packing board is attached to the measuring means. A ground strength determination device, characterized in that the load carrying means is equipped with a probe for transmitting information relating to the amount of subsidence. 2. The packing plate fixing means comprises a post that is vertically installed from above the step and a handle that is installed at the uppermost end of the post so as to be orthogonal to the post. The ground strength determination device according to claim 1.