JPS6183712A - Method of driving quicklime pile - Google Patents

Abstract

PURPOSE:To drive piles so that pile heads are located in a specified level, by a method wherein the discharge pressure of a ground improving material, being applied on the inside of a casing during lifting of the casing, is set to a value about proportioning the volume of the improving material poured in the casing. CONSTITUTION:When, with a casing 2 rotated, the casing is lowered down to a given depth, after rotation of the casing 2 is stopped, a ground improving material, such as quicklime is poured through a hopper 5, and through measurement of the weight by means of a load cell 41, a given amount of the improving material is poured in the casing 2. A shoe 3 is opened, and the casing 2 is lifted up as it is reversed to form a quicklime pile in a ground. In which case, a pipe length L0-L1, being a depth L0 of the casing less a pile head level L1, is computed by a processor 20 to determine a discharge pressure P1, and thereafter, ON and OFF of first and second electromagnetic valves 36 and 38 is controlled so that a discharge pressure is controlled to P1.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention creates piles of quicklime at regular intervals in soft ground, and dewaters the soil by utilizing the water absorbing and expansive properties of quicklime. In the so-called quicklime pile construction method, which improves the ground by compacting the ground, this invention relates to a quicklime pile driving method that aims to always drive the pile head at a constant level.

[Prior art] In general, the driving of piles of soil improvement material containing quicklime as a main component (hereinafter referred to as quicklime piles) is carried out as shown in Fig. 4 (a) and (b) (
c) Performed in the order of (d). In other words, Fig. 4 (
As shown in a), first stand the pile driver (1) vertically at the desired position, and insert the shoe (
3) Rotate the casing (2) with it closed.

The spiral blade (4) allows it to gradually penetrate into the soil.

Next, as shown in Fig. 4(b), the casing (2
) when the tip reaches a predetermined depth (Lo), stop the rotation of the casing (2), and pour the ground improvement material mainly composed of quicklime into the inside of the casing (2) from the upper side hopper (5) at the pile cap level. Inject until it reaches Ll. Next, as shown in FIG. 4(c), the shoe (3) is opened and compressed air is sent from the compressor (6) to pressurize the inside of the casing (2) to a predetermined pressure (Pl).
2) Rotate it in the opposite direction and pull it out. Then, a quicklime pile (7) is created underground as shown in FIG. 4(d). In this way, quicklime piles (7) are driven at predetermined intervals.

The quicklime piles (7) that have been driven absorb water in the surrounding soil, and when they expand, they consolidate the space between the piles and further harden, thereby forming an improved ground.

When constructing quicklime piles using the above method,
It is extremely important that the pile cap level does not vary from construction to construction and is always constant.

However, conventionally, aligning the pile heads relied on the experience and intuition of the person operating the pile driver.

[Problems to be Solved by the Invention] If the method was based on the experience and intuition of experts, the pile cap level would vary greatly depending on individual differences and physical condition, posing a major problem in quality control.

An object of the present invention is to improve accuracy by reducing as much as possible variations in the bowl shape, especially the level of the pile cap, when driving quicklime piles.

[Means to solve the problem] The most important requirements for raising the casing while leaving the quicklime pile in the ground and keeping the pile cap level constant are the volume of quicklime injected into the casing and the casing. This is the internal quicklime pile discharge pressure, and it has been found through numerous experiments that there is a certain relationship between them. Therefore, one aspect of the present invention relates to a method of obtaining a constant pile cap level by pulling out the casing without calculating this relational expression.

Furthermore, the timing of releasing the residual pressure inside the casing to the atmosphere after a certain period of time has passed since the start of lifting the casing is also important. When the casing starts to be pulled up, the air pressure inside the casing gradually decreases due to leakage from the shoe at the tip, etc., which makes it extremely difficult to set the timing for releasing the residual pressure. If the timing of release is too early, the quicklime will rise together with the lifting of the casing (so-called co-up), and the pile cap level will be higher than the set value; conversely, if it is released too late, it will be lower. It has been found through numerous experiments that there is a certain relationship between the residual pressure to be released and the quicklime pile discharge pressure within the casing. That is, it is best to open the inside of the casing to the atmosphere when the residual pressure reaches 173 to 2/3 of the initial discharge pressure. Therefore, the present invention relates to a method of obtaining a constant pile cap level by calculating the relational expression and releasing the residual pressure to the atmosphere when a predetermined residual pressure is reached.

[Example] The present invention will be explained below based on FIG. 1. In addition, the fourth
The same parts as in the figure are given the same reference numerals.

(2) is a cylindrical casing;
The opening (8) at the lower end is provided with a shoe (3) that can be opened and closed and is divided into stripes at intervals of 120 degrees, and a spiral wing (4) is integrally formed on the outer periphery of the upper end. The upper end of the casing (2) has an outer pipe (9) and an intermediate pipe (1).
0), a triple pipe of an internal pipe (11) is provided in a swivel joint state, and a side hopper (5) is provided at the upper end side part. A valve body (12) is provided at the connection between the side hopper (5) and the casing (2), and this valve body (12) is connected to a wire (15) by a piston rod (14) of an external cylinder (13). ) are connected so that they can be opened and closed.

The upper end of the casing (2) includes a motor rotation drive unit (16) including a triple pipe swivel joint, and the pile driver body includes a wire (17) for pulling up the casing (2). are connected, and this wire (17)
is wrapped around the winch (18).

The control circuit for the hydraulic motor (19) of this winch (18) has two systems: automatic control and manual operation.
0), a control valve (22) consisting of an electromagnetic proportional pressure reducing valve, and a pump (23).
), and the manual operation system includes an operation lever (24),
It consists of a pilot valve (25), a valve switching pump (26), and a switching valve (27), and is further provided with a switching switch (2B) and a switching valve (29) for switching between automatic and manual modes.

A weight (3I) is suspended inside the casing (2) by a wire (30), and this wire (30) is led out to the outside through the internal pipe (11) and connected to a pile cap level detection device ( 32) is wound around the weight winch (33). An encoder (34) that interlocks with this weight winch (33) and a motor (35) that rotates the single weight winch (33) are electrically coupled to the processor (20).

The compressor (6) serving as an air source for sending compressed air into the inside of the casing (2) has a first solenoid valve (36).
), connected to the external pipe (9) via a pressure sensor (37), and also a first solenoid valve (36) and a pressure sensor (37).
A second solenoid valve (38) for pressure control is connected between. Furthermore, the compressor (6).

It is connected to the intermediate pipe (10) via a third electromagnetic valve (39), and further connected from the intermediate pipe (10) to the valve opening/closing cylinder (13). And these first, second, and third solenoid valves (36) (38) (39)
is electrically coupled to the processor (20).

The pressure sensor (37) is also electrically coupled to the processor (20) via a pressure transducer (40).

A wire (43) for detecting the penetration depth t, o) of the casing (2) is connected to the casing (2), and this wire (43) is connected to a depth detector (44) to read the data. is sent to the processor (20) every moment.

In addition, (41) is a load cell, and this load cell (41)
1) measures the soil improvement material delivered in a container bag (42) every time it is poured, and the data is sent to the processor (20).
).

A method for driving quicklime piles using the above-mentioned device will be explained. First, as shown in Fig. 4(a), the pile driver (1) is vertically set up at the desired position, the shoe (3) at the tip is closed, and the casing (2) is rotated and driven by the spiral blades (4). Go into the soil. The penetration depth or depth of the casing (2) (
Lo) is detected moment by moment by the depth detector (44) via the wire (43), and the data is sent to the processor (20). As shown in Figure 4(b), the casing (2)
When the tip of the casing (
2) Stop the rotation and pour the soil improvement material from the side hopper (5). At this time, the ground improvement material is delivered in a weight-controlled state in a package such as a container bag, so there is some variation in the unit volume weight (R). Therefore, the weight is measured using a load cell (41), and the data is sent to the processor (20). Since the third solenoid valve (39) is off when the soil improvement material is injected, the cylinder (13)
It is opened to the atmosphere via the intermediate pipe (10) and the third solenoid valve (39), and the valve (12) opens due to the weight of the injected soil improvement material, and is injected into the inside of the casing (2). . When a predetermined amount of soil improvement material is injected into the casing (2),
The third solenoid valve (39) is turned on by a signal from the processor (20), and compressed air from the compressor (6) is supplied to the cylinder (13) via the intermediate pipe (10).
The piston rod (14) descends and the valve (12) closes the communication port between the casing (2) and the side hopper (5).

The height Ll of the ground improvement material packed inside the casing (2) is lowered by a single weight (31), and the wire (30)
The winch up to the signal when no load is applied to the winch (
33) is converted into an electrical signal by an encoder (34), and the data is sent to the processor (20).

When a predetermined amount of the ground improvement material is injected, the shoe (3) is opened and the casing (2) is pulled up while rotating in the opposite direction, so that the quicklime pile (7) is discharged into the soil. At this time, pressure (P+) is required inside the casing (2) to discharge the quicklime pile (7) into the ground. Therefore, the signal from the processor (20)
The solenoid valve (36) is turned on and compressed air is supplied from the compressor (6) to the casing (2) via the external pipe (9). When the supply pressure (Pl) is detected by the pressure sensor (37), it is converted into an electrical signal by the pressure transducer (40), and the data is returned to the processor (20) and the second solenoid valve (38) Opens and closes to control predetermined pressure.

Pressure (P,) required to discharge quicklime pile (7) into the ground
It has been found from the results of numerous experiments that as the volume (Q) of the quicklime pile (7) inside the casing (2) increases or decreases, the characteristic (A) in FIG. 2 changes approximately proportionally. Since the horizontal cross-sectional area of the casing (2) is constant, the volume (Q) is calculated by subtracting the pile cap level (L,) from the height of the filled quicklime pile (7), that is, the casing depth (Lo). Therefore, the discharge pressure (Pl) and the pile length (LO-Ll) are in the range of characteristic (A) in FIG. 2.

Although there are slight differences depending on the nature of the ground and the structure of the casing, it is expected to be roughly proportional.

From the above, the processor (20) determines the pile length (Lo
Based on this, discharge and pressure (Pl) are calculated.
and the first and second
Controls on/off of solenoid valve (36) (3g).

As the casing (2) is pulled up, the compressed air inside leaks from the shoes (3) and the like, and the pressure is gradually reduced. Treatment of residual pressure while the casing (2) is being pulled up from the quicklime pile (7) has a significant effect on the pile cap level (L) and is extremely important. If the timing of determining how much the residual pressure (P2) should decrease relative to the initial discharge pressure (P+) when it should be released to the atmosphere is incorrect, a large difference will occur in the pile cap level (Ll). If the residual pressure (P2) is released too early, the quicklime pile (7) will rise together with the lifting of the casing (2) and reach the pile cap level (
If Ll) becomes higher than the set value and the residual pressure (P2) is released too late, the residual pressure (P2) will cause the pile cap level (
Ll) becomes lower than the set value.

According to numerous experimental results, the appropriate residual pressure (P2
) is the discharge pressure (P+
) is proportional to Therefore, the processor (20) calculates p, -p2=ΔP, and based on the result of this calculation, the first . A predetermined pile cap level (Ll) can be obtained by controlling the second electromagnetic valve (36) (38) and releasing the residual pressure (P2) to the atmosphere at an appropriate time.

In the above-mentioned pouring method, the casing (2) may be pulled up at a constant speed based on the experimental results. However, when the unit volume weight 1 (Rt, ) of the ground improvement material changes, better results can be obtained by changing the pulling speed. In other words, the volume of ground improvement material (
It has been found from numerous experimental results that Q) and the pulling speed (v) are approximately inversely proportional as shown in characteristic (C) in FIG. Ground improvement materials delivered to the site are delivered to container banks (
42), although the unit volume weight (Rj) varies to some extent, and as a result, the volume (Q) injected into the casing (2) varies from pouring to pouring. Changes to Therefore, the weight (G) after inputting is measured by the load cell (4
1), obtain unit volume weight data from the volume (Q) and weight (G), calculate the difference between that data and the set value in the processor (20), and control the lifting speed to an appropriate level based on this. do. That is, when a signal from the processor (20) is input to the amplifier power supply circuit (21), the control valve (
22) is controlled, thereby controlling the amount of oil from the pump (23), and controlling the rotation speed of the hydraulic motor (19) (
v) is controlled. Specifically, when the volume (Q) becomes high, the pulling speed (v) is slowed down, and when the volume (Q) becomes low, the pulling speed (v) is made fast.

As the casing (2) is pulled up, the single-layer fi (31) is lowered. The position of the weight (31) at this time is detected by the pile head level detector (32) and sent to the processor (20). However, the depth detector (44) in the casing (2)
If the position of the weight (31) does not change at all or is abnormally small in response to changes in It is possible that it was not pulled out. Therefore, the depth data and the data from the weight (31) are processed by the processor (20).
) and when an abnormality occurs.

It is also possible to cancel the extraction and further increase the air pressure.

In addition, when pulling up the casing (2) manually, the changeover switch (28) is turned on, the control valve (22) is closed by the changeover valve (29), and the pilot valve (25) is closed via the changeover valve (29). Connect to the pump (23). By operating the operating lever (24), the opening degree of the switching valve (27) is controlled by pressure oil from the pump (23).

The speed of the hydraulic motor (19) is controlled.

[Effects of the Invention] Since the present invention employs the above-described method, the pile cap level is always constant regardless of the level of skill of the operator, and highly accurate quality control is possible. Furthermore, since the driving process can be easily automated, quicklime pile driving can be used for a wider range of civil engineering works.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram for carrying out the method for driving quicklime piles according to the present invention, Figure 2 is a characteristic diagram showing the relationship between the volume of quicklime piles and the internal pressure of the casing, and Figure 3 is the specific gravity of the soil improvement material. An explanatory diagram showing the pulling speed of the casing and the casing, Fig. 4(a)
(b), (c), and (d) are explanatory diagrams of the order of driving quicklime piles. (1)... Pile driver, (2)... Casing, (3)
... Shoe, (4) ... Spiral blade, (5) ... Side hopper, (6) ... Compressor, (7) ...
・Quicklime pile, (12)... Valve, (13)... Cylinder, (18)... Pulling winch, (20)...
・Processor, (21)...Amplifier power supply circuit, (22
)...control valve, (23)...pump, (31)...
... Weight, (32) ... Pile head level detection device, (36
) (3g) (39)...Solenoid valve, (41)...
-Load cell, (44)...depth detector. Applicant Onoda Cement Co., Ltd. Patent Attorney Kano -Kan'-'] 1:"";-L11 (α) 4th Room 2nd Figure 3 Figure 1 Casing 4 Each Thread Q (rI-13) A-

Claims (4)

[Claims] (1) A method in which a casing is driven into soft ground, a ground improvement material containing quicklime as a main component is injected into the casing, and then the casing is pulled up to create a pile in the ground. A method for driving quicklime piles, characterized in that the discharge pressure of the soil improvement material applied inside the casing during pulling up is set to a value approximately proportional to the volume of the soil improvement material injected into the casing. (2) A method in which a casing is driven into soft ground, a ground improvement material containing quicklime as a main component is injected into the casing, and then the casing is pulled up to create a pile in the ground. The discharge pressure of the ground improvement material applied inside the casing during lifting is set to a value approximately proportional to the volume of the ground improvement material injected into the casing, and the residual pressure inside the casing as the casing is pulled up is
A method for driving quicklime piles, characterized in that the inside of the casing is opened to the atmosphere when the initial discharge pressure of the ground improvement material reaches 1/3 to 2/3. (3) The volume of the ground improvement material injected into the casing is
3. A quicklime pile driving method according to claim 1 or 2, wherein calculation is performed from the penetration depth of the casing and the pile head of the ground improvement material. (4) A method in which a casing is driven into soft ground, a ground improvement material containing quicklime as a main component is injected into the casing, and then the casing is pulled up to create a pile in the ground. During lifting, the discharge pressure of the soil improvement material applied inside the casing is set to a value approximately proportional to the volume of the soil improvement material injected into the casing, and the casing pulling speed is set approximately inversely proportional to the volume of the soil improvement material. A method for driving quicklime piles, characterized in that the value is set to a value of