JP6876296B2 - How to measure the depth of the supporting ground - Google Patents

Description

The present invention relates to a method for measuring the depth of a supporting ground, particularly a method for measuring the depth of a supporting ground, which can easily and quickly measure the depth of the supporting ground in a ground improvement work.

In order to construct structures such as railway structures on soft ground, it is necessary to carry out ground improvement work. In this case, the implementation depth of the ground improvement work is generally determined by a ground survey such as a standard penetration test in advance.

When determining the implementation depth of ground improvement work by a ground survey such as a standard penetration test in advance, if the target section becomes long like a railroad track, the depth of the supporting ground should be appropriately and continuously taken into consideration such as inclination. A large number of ground surveys are required to grasp the situation.

FIG. 5 shows an example of a ground survey in which the depth of the supporting ground is determined by a boring survey. As shown in FIG. 5, the depth of the supporting ground 1 changes as shown by the broken line in FIG. 5, and the depth of the supporting ground 1 between the two locations 3a and 3b where the survey boring of the improvement target layer 2 was performed is It is judged that it is inclined linearly.

However, the depth of the supporting ground 1 between the two locations 3a and 3b is actually when it is inclined in a mountain shape as shown by the alternate long and short dash line in FIG. 5, or as shown by the alternate long and short dash line in FIG. , It is quite possible that it is inclined in a valley shape.

The ground improvement is performed, for example, by constructing a plurality of improvement piles 4 on the improvement target layer 2 as shown in FIG. As for the implementation depth, the supporting ground is confirmed during the construction of the improved pile 4, but if the improvement target layer 2 between the two locations 3a and 3b is inclined in a mountain shape, the improved pile 4 is constructed to an extra depth. There is a risk of On the other hand, when the improvement target layer 2 between the two locations 3a and 3b is inclined in a valley shape, the improvement pile 4 may not reach the supporting ground 1. Further, even if the improved pile 4 is constructed up to the actual supporting ground, the construction efficiency may decrease due to a sudden change in the work process and material supply, unlike the initial construction plan.

For this reason, it is important for ground improvement work to grasp the depth of the supporting ground in advance and perform ground improvement commensurate with the depth.

As a countermeasure for this, as described above, there is a method in which the depth of the supporting ground is determined by a large number of ground surveys in consideration of the inclination and the like, but such a method requires a large amount of construction cost and time.

For this reason, it is desired to develop a method for measuring the depth of the supporting ground, which can easily and quickly measure the depth of the supporting ground, but the present situation is that such a method has not yet been proposed.

Therefore, an object of the present invention is to provide a method for measuring the depth of the supporting ground, which can be easily and quickly measured in the ground improvement work, as compared with the case where the depth of the supporting ground is measured by a large number of ground surveys. There is.

The present invention has been made to achieve the above object, and is characterized by the following.

The invention according to claim 1 is a method for measuring the depth of a supporting ground, in which a plurality of sets of simultaneous constant microtremor observations of an arbitrary reference point on the ground surface and an observation point spaced apart from the reference point are performed. From the constant tremor waveform obtained by the constant tremor observation, the vertical Fourier spectrum ratio from the reference point in each observation set was obtained, and the peak period difference observed in the vertical Fourier spectrum ratios of the two sets was obtained. Based on the above, the depth difference of the supporting ground between the two observation points is obtained from the peak period difference, and the supporting ground is used by using the depth difference and the depth found from the ground survey conducted at any of the observation points. It is characterized by measuring the depth of.

The invention according to claim 2 is evaluated from the numerical analysis result in the invention according to claim 1, according to the following equation (1).
ΔH = F (ΔT, Vs) --- (1)
However, in equation (1),
ΔH: Depth difference of supporting ground,
ΔT: Peak period difference,
Vs: Rigidity of improved ground,
It is characterized in that it is obtained based on.

The invention according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the inclination of the supporting ground is grasped by the depth of the supporting ground by the plurality of sets.

According to the present invention, in the ground improvement work, the depth of the supporting ground can be measured easily and in a short time as compared with the case where a large number of ground surveys are conducted.

It is an explanatory diagram of the basic principle of constant tremor observation at two observation points at the same time. It is a graph which shows the Fourier spectrum ratio. It is a graph which shows the relationship between the peak period difference and the depth difference of the supporting ground based on the numerical analysis result. It is sectional drawing which shows the depth measuring method of the supporting ground by this invention. It is sectional drawing which shows an example of the ground investigation. It is sectional drawing which shows the ground improvement method by the improvement pile.

The basic principle of the method for measuring the depth of the supporting ground of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of the basic principle of constant tremor observation at two observation points at the same time, FIG. 2 is a graph showing a Fourier spectral ratio, and FIG. 3 is a relationship between a peak period difference based on numerical analysis results and a depth difference of the supporting ground. It is a graph which shows.

As shown in FIG. 1, the method for measuring the depth of the supporting ground according to the present invention is an arbitrary reference point P on the ground surface of the improvement target layer 2 on the supporting ground 1 and an observation point A separated from the reference point P. A microtremor meter 5 is installed at the same time to simultaneously observe the constant microtremors at the reference points P and A.

Next, a tremor meter 5 is installed at the reference point P and the B observation point at intervals, and the constant tremor at the reference point P and the B observation point is simultaneously observed. That is, two sets of constant tremor observations are performed simultaneously with the reference point P on the ground surface. FIG. 1 shows set AB and set BC as such a set.

Next, the vertical Fourier spectrum ratio from the reference point P at the two observation points is obtained from the constant tremor waveform obtained by the constant tremor observation, and the peak period difference ΔT seen in this vertical Fourier spectrum ratio is obtained (see FIG. 2). ). _{The periodic difference ΔT AB} between the A observation point and the B observation point is evaluated _{from the set AB, and the periodic difference ΔT BC} between the B observation point and the C observation point is evaluated from the set BC.

Next, the depth difference ΔH of the supporting ground between the two observation points is obtained from the peak period difference ΔT based on the numerical analysis formula (see FIG. 3). _{The depth difference ΔH AB} between the A observation point and the B observation point is evaluated _{from the set AB, and the depth difference ΔH BC} between the B observation point and the C observation point is evaluated from the set BC.

Here, the numerical analysis formula is composed of the following formula (1).

ΔH = F (ΔT, Vs) --- (1)
However, in equation (1),
ΔH: Depth difference of supporting ground,
ΔT: Peak period difference,
Vs: Rigidity of improved ground.

Here, if the ground survey is carried out at any of the observation points A, B, and C and the depth is known, the depths of the other observation points can be measured. For example, when the depth L3 is known at the A observation point, the depths L1 and L2 of the supporting ground 1 at the B observation point and the C observation point can be measured based on the depth difference ΔH. Further, by obtaining the depth difference ΔH, the inclination state of the supporting ground 1 can be grasped from the depth difference ΔH and the distance between the two observation points.

The depth L1 of the supporting ground 1 at the B observation point is the sum of the depth L3 of the supporting ground 1 at the A observation point and the depth difference ΔH _AB . The depth L2 of the supporting ground 1 at the observation point C is the depth L1 of the supporting ground 1 at the observation point B plus the _{depth difference ΔH BC.}

According to the present invention, in order to actually measure the depth of the supporting ground, as shown in FIG. 4, simultaneous continuous microtremor observation with the reference point 6 and the microtremor 5 is performed at a plurality of locations including the boring survey location 3. For example, as described above, the depth of the supporting ground 1 in the section where the constant tremor observation is carried out and the inclination of the supporting ground 1 in this section can be measured based on the depth.

As described above, according to the present invention, the depth of the supporting ground in the ground improvement work can be measured more easily and in a shorter time than in the case of conducting a large number of ground surveys by constantly performing microtremor observation. Can be done.

1: Supporting ground 2: Improvement target layer 3: Boring survey location 4: Improved pile 5: Microtremor 6: Reference point

Claims (3)

This is a method for measuring the depth of the supporting ground. On the ground surface, a plurality of sets of simultaneous constant tremor observations of an arbitrary reference point and observation points spaced apart from the reference point are performed, and the constant tremor waveform by the constant tremor observation is performed. From, the vertical Fourier spectrum ratio from the reference point in each observation set was obtained, the peak period difference observed in the vertical Fourier spectrum ratios of the two sets was obtained, and the peak period difference was obtained based on the numerical analysis result separately performed. The depth difference of the supporting ground between the two observation points is obtained, and the depth of the supporting ground is measured by using the depth difference and the depth found from the ground survey conducted at any of the observation points. The method of measuring the depth of the supporting ground. The numerical analysis result is obtained by the following equation (1).
ΔH = F (ΔT, Vs) --- (1)
However, in equation (1),
ΔH: Depth difference of supporting ground,
ΔT: Peak period difference,
Vs: Rigidity of improved ground,
The method for measuring the depth of the supporting ground according to claim 1, wherein the method is obtained based on the above. The method for measuring the depth of a supporting ground according to claim 1 or 2, wherein the inclination of the supporting ground is grasped by the depth of the supporting ground by the plurality of sets.

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