JPH0474517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a deep ground loading test method and apparatus, in which a soil retaining liquid such as bentonite is injected into the tip of a hole drilled in the ground, and cement milk, mortar, etc. Fill the hole with a hardening liquid, insert a loading pipe with a loading plate at the tip into the hole, fix the loading pipe to the surrounding ground with the hardening liquid, and use the peripheral surface friction resistance of the fixed loading pipe as a reaction force. , a deep ground loading test method characterized by determining the bearing capacity of the ground at the tip of the loading pipe by examining the amount of pushing movement of the loading plate into the ground and the upward displacement of the loading pipe in relation to the applied load. The specified invention also includes a loading plate that is pushed down by a loading jack installed in the loading pipe and is slidably disposed below the loading pipe, the sliding portion is formed in a sealed state, and the loading plate is The combined invention is a loading test device for deep ground, characterized by comprising a loading plate displacement measuring means and a loading pipe displacement measuring means for measuring the amount of pushing movement and upward displacement of the loading pipe on the ground. be.

In general, the flat plate loading method has traditionally been used to investigate and measure the so-called soil bearing capacity, such as the strength and deformation of the ground. In this method, the ground to be investigated is excavated, a loading plate is installed on the ground surface of the excavated area, and the loading plate is pressurized (loaded) with jacks using reaction beams and reaction loads, and then separately This method measures the movement of the loading plate during each loading using a dial gauge attached to a fixed beam, and investigates the strength, deformation, etc. of the ground, but since it is carried out by excavating the ground, it is difficult to directly examine the ground. Although it has the advantage of being able to survey and measure the ground, it has the disadvantage that its applicability is limited to the vicinity of the ground surface.

The present invention was invented in view of the above points, and its purpose is to enable direct flat loading even in deep ground, to grasp the properties of the supporting ground, and to secure the loading pipe to the surrounding ground. To provide a deep ground loading test method and device that is simple and inexpensive, without requiring a separate reaction pile or load, since the load can be applied using large frictional resistance with the surrounding ground as a reaction force.

The present invention will be explained in detail below with reference to Examples. FIG. 1 shows an embodiment of the apparatus used in the present invention.
The loading pipe 3 is made of a steel pipe like a steel pipe pile, and has a tapered portion 8 at its lower part. A reaction ring 9 is fixed to the lower part of the inner wall of the loading pipe 3, and a loading jack 6 is attached to the lower surface of the reaction ring 9 via a mounting plate 10. In the figure, 11 is a bolt hole.
12 is a bolt. In addition, the reaction ring 9 and the mounting plate 10 have an insertion hole 13 for inserting the displacement measurement elongated member 7, a hydraulic hose insertion hole 14 for inserting the hydraulic hose, and a measurement cord for inserting the measurement cord 15. An insertion hole 16 is provided. 1 in the diagram
Reference numeral 7 denotes a rib that reinforces the adhesion between the reaction ring 9 and the loading tube 3, and is fixed to the reaction ring 9 and the loading tube 3. In other words, the reinforcing ribs 17 serve to prevent the reaction ring 9 from deforming upward when a large force is applied to the reaction ring 9 from below. Load jack 6
A displacement plate 18 is provided at the bottom of the displacement plate 18.
A loading platform 19 is arranged in series at the bottom of the loading platform 1.
9 is inserted into the lower end opening 20 of the loading tube 3, and the loading plate 5 is provided at a portion of the lower end of the loading platform 19 that projects downward from the lower end opening 20. Here, a gasket 21 is provided between the lower end opening 20 and the loading platform 19 to prevent muddy water. The lower end of the tubular or rod-shaped displacement measuring elongated member 7 is fixed to the displacement plate 18, and the displacement measuring elongated member 7 is inserted into each insertion hole 13 of the mounting plate 10 and the reaction ring 9. It is inserted into a hole 23 of a support 22 fixed to the inner wall of the loading tube 3, and its upper end is located near the opening of the upper end of the loading tube 3. The hydraulic hose 4 is inserted into the hydraulic hose insertion hole 14 and led out from the upper end opening of the loading pipe 3.
The measurement cord 15 connected to the measurement cord insertion hole 1
6 and is led out from the upper end opening of the loading tube 3. Note that here, a support 22 that fixes the hydraulic hose 4 and the measurement cord 15 to the inner wall of the loading pipe 3 is used.
Alternatively, the protective tube may be secured to the support 22 and inserted into the protective tube along the inner wall of the loading tube 3. The strain gauge 24 is used to measure the strain and loading load of the loading platform 19 with precise accuracy, but since the loading platform 19 slides up and down on the gasket 21 of the lower end opening 20 of the loading tube 3, it has a cylindrical shape. The measurement cord 15 is embedded in the inner surface of the loading platform 19 so that the measurement cord 15 is not exposed to the outside of the loading platform 19. A deep ground loading test is performed using the above device as shown in Figure 2. That is, first, as shown in FIG.
Dig the hole to around the specified depth. Next, as shown in Fig. 2b, when the screw auger 25 is pulled up into the hole 2 drilled in the ground 1, bentonite 26 is applied to the bottom of the hole 2 from the tip nozzle of the screw auger 25 to prevent collapse of the hole wall and the ground. A hardening liquid 27 such as cement milk or mortar is injected into the soil holding liquid. Next, as shown in Figure 2 c, the loading pipe 3 is suspended and inserted into the hole 2, and then, as shown in Figure 2 d, a supplementary load is applied, and the loading pipe 3 is lightly moved to the predetermined ground 1 using the auger reducer 28. (By passing the bentonite liquid part and press-fitting the part disturbed by excavation, the tip part of the loading pipe 3 including the loading plate is positioned in the predetermined tip ground 1). Here, the hardening liquid 27 such as cement milk or mortar hardens and the loading pipe 3
A large frictional resistance is generated between the pipe and the surrounding ground, and the loading pipe 3 is immovably fixed to the surrounding ground. In this case, even if the loading pipe 3 is suspended and inserted into a hole filled with cement milk, mortar, etc., the opening 2 at the lower end of the loading pipe allows the loading plate 5 to slide.
0 is formed in a sealed state with a packing 21 or the like, so that the cement milk and the like will not enter (into) the loading pipe and harden the internal hydraulic jacks, instruments, etc. Now place bentonite 2 at the bottom of hole 2.
6 was injected because if the hardening liquid 27 was injected to the bottom of hole 2, the hardening liquid 27 would enter the specified ground below hole 2 to be tested and solidify, making it impossible to perform the specified loading test. . Next, as shown in Fig. 2e, a fixed beam 29 is installed on the ground, and a dial gauge 3 is used as a loading plate displacement measuring means for measuring the amount of pushing movement of the loading plate 5 provided on the fixed beam 29.
0, and the end of the hydraulic hose 4 is connected to the hydraulic pump 31. Further, the immovable beam 29 is provided with a displacement measuring device 32 serving as a loading tube displacement measuring means for measuring the displacement of the loading tube 3. Using the frictional resistance around the upper part of the loading pipe 3 as a reaction force, the loading plate 5 is operated by the loading jack 6 to push the loading plate 5 into the deep ground 1. Then, the displacement measurement length corresponds to the movement of the loading plate 5. The bearing capacity of the deep ground 1 is measured by moving the length member 7 and measuring the amount of movement using a loading plate displacement measuring means such as a dial gauge 30 for measuring the amount of pushing movement of the loading plate. be. Here, the loading pipe 3 is temporarily fixed to the surrounding ground and is immovable, but if the frictional resistance with the surrounding ground is small, the loading pipe 3 may rise slightly when the loading plate 5 is pushed. In such a case, the lifting of the loading pipe 3 is measured using the displacement measuring device 32 of the loading pipe 3 to obtain a more accurate bearing capacity of the deep ground 1. Further, when a load is applied, the loading platform 19 may be distorted, but in this case, the strain is measured by the strain meter 24 to obtain a more accurate bearing capacity of the deep ground 1.

FIG. 3 shows another embodiment of the apparatus for use in the present invention. In this embodiment, a reaction ring 9 is fixed near the upper end inside the loading pipe 3, and a loading jack 6 is attached to the lower surface of the reaction ring 9 via a mounting plate 10. . A push pipe 34 is attached to the lower part of the loading jack 6 via a lower mounting plate 33, a displacement plate 18 is provided at the bottom of the push pipe 34, and a loading platform 19 is provided at the bottom of the displacement plate 18. A loading plate 5 is provided at the bottom of 19. Here, a plurality of guide parts 35 are provided on the outer circumferential surface of the push pipe 34 projecting upward and downward, and the loading jack 6 presses the loading plate 5 through the push pipe 34. The portion 35 allows the push tube 34 to move straight within the loading tube 3 without tilting. Note that the loading jack 6 and the like described above may be installed after the loading pipe 3 is suspended and press-fitted into the hole 2.

By the way, in the embodiment shown in FIG. 1, since the loading jack 6 is disposed inside the loading tube 3, the push tube 3
4 is not required, and there is no error caused by distortion of the push tube 34. On the other hand, in the embodiment shown in FIG. 3, since the loading jack 6 is disposed near the head of the loading pipe 3, the loading jack 6 etc. can be recovered and reused.

In the first aspect of the present invention, a soil retaining liquid such as bentonite is injected into the tip of a hole drilled in the ground, and a hardening liquid such as cement milk or mortar is filled in the upper part of the hole, and the tip of the hole is filled with a hardening liquid such as cement milk or mortar. A loading pipe equipped with a loading plate is inserted and placed, and the loading pipe is fixed to the surrounding ground with the above-mentioned hardening liquid, and the amount of displacement of the loading plate into the ground is determined by using the circumferential frictional resistance of the fixed loading pipe as a reaction force. In order to determine the bearing capacity of the ground at the tip of the loading pipe by examining the upward displacement of the loading pipe in relation to the applied load, the outer circumferential surface of the loading pipe is completely bonded to the hole wall ground using a hardening liquid such as cement milk or mortar. It can be fixed and loaded using the circumferential frictional resistance between the outer circumferential surface of the loading pipe and the hole wall ground as a reaction force. Moreover, when filling the hole with a fixing liquid and completely fixing the outer peripheral surface of the loading pipe to the hole wall ground with the hardening liquid, a soil retaining liquid such as bentonite is injected into the lower part of the hole. This prevents the hardening liquid from entering and hardening the specified ground below the hole where the test is to be performed, and allows the specified loading test to be performed by allowing the hardening liquid to enter and harden at the location below the hole where the test is to be performed. We are trying to prevent this from happening. In this way, the present invention fixes the loading pipe to the ground of the hole wall with a hardening liquid filled in the upper part of the hole, and also fills the lower part of the hole with bentonite, thereby improving the stability of the loading pipe, including the loading plate that presses against the ground. This means that the tip is buried in the ground at a predetermined depth, restrained by the ground soil in the same manner as when a foundation pile is driven, and when a load is applied to the loading plate, the tip is buried in the ground. There is no space for the pile to escape, and it is possible to accurately determine the bearing capacity of the tip of the pile, that is, the bearing capacity of the ground at the tip. In addition, unlike conventional methods, separate reaction piles and loading loads are not required, making it simple and cost-effective.Also, whereas conventional pile loading tests are performed after the reaction piles are driven, this method With this method, you can test the pile before driving it, and moreover, you can accurately determine the bearing capacity of the ground at the tip, which is essential for the bearing capacity of the pile. Moreover, the loading pipe is fixed to the surrounding ground and is immovable, but if the frictional resistance with the surrounding ground is small, the loading pipe will rise slightly when the loading plate is pushed in, but the loading pipe may not move or Measure the displacement of the load to see if it has risen a little, and even if the loading pipe has risen a little, check the displacement of the loading plate into the ground and the upward displacement of the loading pipe in relation to the applied load. This has the effect of being able to accurately determine the bearing capacity of the ground at the tip of the pipe.

In addition, in the second aspect of the present invention, a loading plate that is pushed down by a loading jack installed in the loading pipe is slidably arranged below the loading pipe, and the sliding portion is formed in a sealed state. At the same time, since it is equipped with a loading plate displacement measuring means and a loading pipe displacement measuring means for measuring the pushing movement amount of the loading plate and the upward displacement of the loading tube on the ground, bentonite is injected into the lower part and hardening liquid is injected into the upper part. When inserting the loading tube by suspending it into the hole where it was injected, and after insertion, the hardening liquid and bentonite may infiltrate into the loading tube from the sliding part of the loading plate that can freely slide downwards from the loading tube, causing damage to the internal equipment. The load plate shall not have any adverse effect on or be damaged, nor will it interfere with the smooth movement of the loading plate. Moreover, since it is equipped with a loading plate displacement measuring means and a loading tube displacement measuring means for measuring the amount of pushing movement of the loading plate and the upward displacement of the loading tube on the ground, it is possible to ensure that the loading tube does not move during the loading test. Alternatively, the loading pipe displacement measuring means measures whether the loading pipe has risen a little, and even if the loading pipe has risen slightly, the value measured by the loading plate measuring means can be corrected with the value measured by the loading pipe displacement measuring means. It is possible to obtain a more accurate bearing capacity of the deep ground.

[Brief explanation of the drawing]

Figures 1 a, b, and c are longitudinal cross-sectional views, cross-sectional views, and cross-sectional views of other parts of one embodiment of the device used in the present invention, and Figures 2 a, b, c, d, and e are the main views, respectively. An explanatory diagram showing the order of the invention method, and FIG. 3 is a sectional view of another embodiment of the device used in the invention, in which 1 is the ground, 2 is a hole, 3 is a loading pipe, 5 is a loading plate, and 6 is a sectional view of another embodiment of the device used in the invention. Loading jack 7 is a displacement measuring elongated member.

Claims (1)

[Claims] 1. Injecting a soil-retaining liquid such as bentonite into the tip of a hole drilled in the ground, and filling the upper part with a hardening liquid such as cement milk or mortar,
A loading pipe with a loading plate at the tip is inserted into the hole, and the loading pipe is fixed to the surrounding ground with the hardening liquid, and the friction resistance on the circumferential surface of the fixed loading pipe is used as a reaction force to cause the loading plate to penetrate into the ground. A loading test method for deep ground, which is characterized by determining the bearing capacity of the ground at the tip of a loading pipe by examining the amount of displacement and upward displacement of the loading pipe in relation to the applied load. 2. A loading plate that is pushed down by a loading jack installed in the loading pipe is slidably arranged below the loading pipe, and the sliding portion is formed in a sealed state, and the amount of pushing movement of the loading plate and the loading pipe are 1. A loading test device for deep ground, comprising a loading plate displacement measuring means and a loading pipe displacement measuring means for measuring upward displacement of the soil on the ground.