JPH0684619B2 - Root cutting method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a root cutting method for constructing a foundation or the like of a building, and more particularly to a root cutting method suitable for deep-depth root cutting exceeding 20 m. .

[Prior art]

In general, when performing root cutting, a soil retaining wall such as a continuous wall reaching an impermeable layer is provided around the root to prevent ground subsidence around the surrounding area and increase the amount of pumped water, and perform root cutting.

However, in the case of deep root cutting exceeding 20 m, a deep retaining wall more than the depth to be excavated is required, but there is a possibility that the root cutting bottom ground generally called heaving or boiling will occur. , I needed to prevent this.

In most cases, the Quaternary layer has a clay layer in the shallow area, and the deep layer mainly has sand and gravel layers, and a large water pressure is applied. Moreover, although this sand layer is generally a dip layer and has high strength, it has the property of allowing water to easily pass through, and this water treatment has been a major problem when root cutting.

[Object of the Invention]

The present invention has been made in view of the above problems. The purpose is to propose a root cutting method that enables deep root cutting with a relatively small pumping volume without the need to make the retaining wall extremely deep.

[Structure of Invention]

The root cutting method that becomes the invention of (1) is a root cutting method in which the circumference is surrounded by a mountain retaining wall that reaches a water impermeable layer deeper than the bottom, and the inside is pumped to perform root cutting.
It is characterized in that the impermeable layer located deeper than the root cutting bottom and the hard layer located deeper than the root cutting are connected by anchor piles.
In the root cutting method of the invention of (2), when there is no impermeable stratum at an appropriate depth below the root cutting bottom, a hardener is injected into the depth below the root cutting bottom to cut the impermeable layer before root cutting. It is characterized in that this impermeable layer is connected to the hard layer located deeper by an anchor pile.

〔Example〕

The embodiment will be described below. In FIGS. 1 and 2, a continuous wall 4 is built around the ground 1 to be root-cut and reaches a water-impermeable layer 3 made of a clay layer deeper than the root-cutting bottom 2 in the hard sand layer. With a cast-in-place concrete pile driving machine, the tip extends to the hard layer 5 which is deeper than the impermeable layer 3 and has the largest diameter near the root cutting bottom in a grid pattern at intervals of 5 to 10 m in the ground. Drill a hole. PC in the vertical muscle in this pit
A steel wire is used, a pressure bearing plate 6 is attached to the tip, and a reinforcing bar cage 7 whose length reaches the root cutting bottom 2 from the hard layer 5 is suspended. Concrete is poured into this drilled hole to form an anchor pile 9 which penetrates the impermeable layer 3 from the hard sand layer 8 having the root cutting bottom 2 and reaches the hard layer 5 in the deep layer. The anchor pile 9 has a diameter increased at the upper end, has a maximum diameter near the root cutting bottom 2, and connects the impermeable layer 3 and the hard layer 5 located below.

The vertical holes shallower than the root cutting bottom 2 are backfilled with soil cement or the like so as not to obstruct the root cutting. In this state, the ground is pumped up, excavated, and root cutting is performed up to the root cutting bottom 2.

In this embodiment, the upper end of the anchor pile is fixed to the upper hard sand layer of the impermeable layer to connect the impermeable layer and the hard layer to improve the connection strength between the impermeable layer and the relatively impermeable layer. Although it is intended, various other modes can be adopted.

When the water-permeable layer does not exist at an appropriate depth position, as shown in FIG. 3, a hardener is injected into the hard sand layer 8 deeper than the root cutting bottom 2, for example, to create an artificial impermeable material having water impermeability and strength. A water permeable layer 3'is formed.

Also in this case, as in the case of FIG. 1, vertical holes are drilled at a predetermined interval, the rebar cages 7 are suspended, the hard layer 5 reaches the root cutting bottom 2, and the maximum diameter near the root cutting bottom is reached. Anchor pile 9
And the impermeable layer 3 ′ is connected to the hard layer 5 located deeper.

[Work]

This construction method consists of the above structure.Before root cutting, a water impermeable layer deeper than the root cutting bottom or an artificial water impermeable layer formed by injecting a hardening material is a hard layer and an anchor deeper than that. Connect with piles. Therefore, as shown in Fig. 4, when the ground 1 surrounded by the connecting walls 4 is pumped up and root cutting is performed,
The groundwater pressure P acts on the lower surface of the impermeable layer 3 '. However, tension T commensurate with this water pressure P is automatically generated in the anchor pile 9 to maintain the balance and prevent the root cutting bottom 2 from being broken.

Since the anchor pile of the example has an expanded upper end, the groundwater pressure acting on the lower surface of the impermeable layer acts as a compressive force on the reverse taper portion of the anchor pile, so the anchor pile surrounding hard The sand layer 5 or the water impermeable layer 3, 3'is required to have sufficient strength and water impermeability. Moreover, as a result, the connection strength between the anchor pile and the impermeable layer or the hard sand layer can be increased.

〔The invention's effect〕

In the conventional root cutting method, even if there is an impermeable layer such as a clay layer, it is necessary to pump water in an amount corresponding to the difference between the load acting on the upper surface and the groundwater pressure acting on the lower surface. For cutting, a deep soil retaining wall and a large amount of pumping had to be done, but this method allows a relatively shallow soil retaining wall to be built, and a small amount of pumping to deep root the soil.

In addition, if there is no impermeable layer at an appropriate depth, it is necessary to go down the mountain retaining wall very deeply in the past, and the construction period and construction cost would be extremely expensive, and construction was sometimes impossible. Even in such a case, it is possible to efficiently perform deep root cutting.

[Brief description of drawings]

The drawings show the construction method of the embodiment, and FIG. 1 and FIG. 2 are a longitudinal sectional view and a plan view showing an example of construction of the ground having a water impermeable layer, and FIG. Sectional drawing which shows the construction example of the ground which formed the layer, FIG. 4 is sectional drawing after root cutting. 1 ... Root cutting ground, 2 ... Root cutting bottom, 3 ... Impermeable layer, 4 ... Continuous wall, 5 ... Hard layer, 6 ... Pressure plate, 7 ...
… Reinforcing cage, 8 …… Hard sand layer, 9 …… Anchor pile.

Claims (2)

[Claims] 1. A root cutting method in which the surrounding area is surrounded by a mountain retaining wall reaching a water impermeable layer deeper than the root cutting bottom and the inside is pumped to perform root cutting. A root cutting method characterized by connecting a flexible layer and a hard layer that is deeper than that with an anchor pile. 2. In a root cutting method in which the circumference is surrounded by a mountain retaining wall that reaches an impermeable layer deeper than the root cutting bottom, and the inside is pumped to perform root cutting, a hardening material is provided deeper than the root cutting bottom before root cutting. A root cutting method comprising injecting a water-impermeable layer and connecting the water-impermeable layer with a harder layer located deeper by an anchor pile.