JPS626049B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an earth retaining wall construction method on sandy and gravel ground.

Generally, when constructing underground structures such as subways in urban areas, it is necessary to construct earth retaining walls using steel sheet piles, H-shaped steel, etc. prior to excavation to prevent the surrounding ground from collapsing or subsidence due to excavation. Sheet piles and H
Driving shaped steel using the normal falling weight driving method or vibration driving method produces intense noise and vibration, which can cause damage to neighboring houses.
For this reason, it is necessary to drill into the ground with an auger in advance and erect H-beams, etc., or in soft ground, to prevent the wall of the hole excavated with an auger from collapsing, when pulling out the auger rod, cement milk or bentonite liquid is poured from the tip of the rod. Alternatively, a method is used in which a mixture of the two is injected and H steel is erected immediately after the auger rod has been pulled out, or a concrete underground continuous wall is installed.

However, injecting cement milk or bentonite from the tip of the auger rod requires drilling → pouring → erection → when erecting H-shaped steel at regular intervals like a so-called horizontal sheet retaining wall with H-shaped steel as the parent pile.
The work proceeds in the order of drilling, but for items such as steel sheet piles that must be erected continuously, the hardening agent that has been poured into the holes will solidify in advance and provide a certain level of strength. If not, the adjacent auger rod that will be drilled later will slide toward the preceding drilling hole, making it difficult to perform vertical construction. This is particularly dangerous if the ground is hard, such as sand and gravel. Furthermore, in cases where the ground contains large gravel or where groundwater flows as underground water, it is extremely difficult to construct an underground concrete wall, and in many cases it is impossible. Therefore, it is almost impossible or economically very expensive to construct a water-stopping earth retaining wall on such ground. For example, when drilling with an earth auger and erecting steel sheet piles are performed consecutively as shown in FIG. 1, the holes are first drilled in sequence. In this case, 1 in the figure,
Reference numerals 2, 3, and 4 indicate holes into which a hardening agent was injected after drilling with an earth auger, and reference numerals 6, 7, and 8 indicate steel sheet piles that have been filled in the holes 1, 2, and 3 mentioned above. 5 indicates the position of the next hole to be drilled, and 9 indicates the steel sheet pile to be built next.

Since the steel sheet piles must be jointed to each other by the section portions 10, if the drilling of the next adjacent hole 5 is not completed before the steel sheet pile 9 is erected, the auger rods will not be formed after the steel sheet pile 9 is erected. comes into contact with the section section 10' of the steel sheet pile 9, so
5 cannot be drilled.

It is understood that two or more ocher holes must be drilled in advance when constructing such steel sheet piles, but if cement milk is used as a hardening agent and construction is to be carried out consecutively, it is necessary to drill two or more ocher holes first. If the next hole 5 is drilled before the hardening agent in the drilled hole 4 has yet solidified, the auger rod will slide to the side of the hole 4 which is softer than the surrounding ground, making it impossible to drill the hole 5 in the correct position. This tendency is particularly strong when the foundation ground is hard, such as sandy gravel.

Therefore, in order to erect several steel sheet piles in a row in one day, as shown in Figure 2, it is necessary to drill multiple holes with an auger every other sheet, inject cement, and allow the cement to harden. The next day, the intermediate holes are drilled and poured, and then the steel sheet piles are erected one after another.

However, in such a conventional method, the order of drilling and pouring and the erection of sheet piles and the time constraints are very large, so the workability of the work is very poor. In other words, the strength of cement milk or a mixed suspension with bentonite develops over time, so if the subsequent sheet pile erection is delayed for several days after drilling, pouring, rain or other operational reasons, the strength of cement milk will deteriorate. becomes large, making it impossible to erect the sheet pile, or erecting it by vibration driving or strong jacking becomes necessary.

Furthermore, if the strength of the cement milk becomes greater than the strength of the surrounding ground, the steel sheet piles will tend to flow toward the surrounding ground during erection, and the original purpose of building sheet piles by auger excavation will be lost. .

That is, in the present invention, a ground auger or the like is used to drill into the ground in advance to loosen the ground at the location of the hole, and while the auger rod is being pulled out, a hardening agent suspension is injected into the hole from the tip of the rod to transform the soil into a hardening agent suspension. In the earth retaining method, in which a steel sheet pile is inserted into the pile and this is repeated continuously to form an earth retaining wall underground, a mixture of hemihydrate gypsum and purified clay with an appropriate amount of setting retardant added as a hardening agent suspension is used. By using a suspension or a suspension in which an appropriate amount of Portland cement is mixed, it is possible to arbitrarily set the setting start time of the hardening agent and to greatly increase the strength over time after the desired initial strength is reached. By making it slow, it was possible to improve the workability of subsequent steel sheet pile erection work and auger excavation, and to avoid noise and vibration.

In the present invention, the ``method of injecting a hardening agent suspension from the tip of the rod while pulling out the auger rod, and inserting a steel sheet pile inside'' is known as the PIP method, and is a water-stop wall construction method (Japanese Patent Laid-Open No. 51 −131117
No.) has been proposed. A new requirement of the present invention is the use of a set retarder, gypsum hemihydrate, a mixture of natural or purified clay, or a suspension thereof mixed with Portland cement, as the hardening agent suspension.

Next, a water stop wall construction method using a gypsum suspension (Japanese Unexamined Patent Publication No. 152610/1982) is also known. This prior art uses a suspension made by adding cement and/or bentonite to a gypsum suspension, and since bentonite is expensive, the construction cost is extremely high.
The present invention aims to save construction costs by using clay that is easy to handle and inexpensive. Furthermore, the present invention adds a setting retardant to the suspension, which is not found in the prior art, and this makes it possible to erect steel sheet piles even after several days have passed, making the work of erecting steel sheet piles easier. .

The present invention eliminates the above-mentioned drawbacks, sets the coagulation time of the hardener suspension arbitrarily to develop the required strength in a short time, and enables continuous drilling with an auger, thereby reducing the work of drilling and pouring. After the steel sheet pile erection work can proceed in parallel with each other and the required strength of the hardener suspension is achieved in a short time,
The hardening agent was selected so that the strength would increase very slowly over time, so that even if the steel sheet pile erection was delayed by several days or a week, the erection work would not be affected in any way. This combination has made it possible to carry out earth retaining work in urban areas without noise or vibration, even on sandy and gravelly ground.

Note that bentonite is mined in mines in Yamagata Prefecture, Gunma Prefecture, etc., and is crushed and packed into bags, which is extremely expensive. This bentonite has excellent swelling properties, thickening properties, and liquid property limits, and is essential when excavating trenches using the no-casing construction method.However, due to its swelling properties, workability is not good in the earth retaining wall construction method of the present invention. . In contrast, the present invention uses natural clay that is available nearby depending on the work location, and if the work location is in an urban area or its surrounding area and it is difficult to obtain natural clay, the natural clay is purified by passing it through a sieve and packing it into bags. Use clay. These natural or purified clays are extremely inexpensive, and hardener suspensions made by mixing clay with gypsum, cement, etc. develop initial strength quickly, but the subsequent increase in strength is slow. Therefore, it has significantly better workability than bentonite.

The present invention will be described below based on the embodiment shown in FIG. 1. First, a desired hole 1 is bored in a desired ground using the earth auger method. After drilling to the target depth, the earth auger rod is pulled out. In this case, a suspension of hemihydrate gypsum and natural or purified clay, to which an appropriate amount of setting retardant has been added, or an appropriate amount of Portland cement is mixed in from the tip of the earth auger rod. Inject the suspension. That is, the auger rod is withdrawn while the suspension is being injected to replace the soil in the borehole with a hardener suspension, and then, when the suspension injected into the borehole has reached the desired initial strength, The next hole 2 adjacent to the drilled hole 1 is similarly drilled with an earth auger, and the hardening agent suspension is injected when the auger rod is pulled out. Furthermore, after the curing agent in hole 2 has hardened, a third hole 3 is bored and the suspension is injected into it. In this way, the holes are drilled one after another, and when at least the second hole has been drilled and the injection is completed, the desired steel sheet pile 6 is built into the hardened material of the first hole 1. Further, after the drilling and injection of the third hole 3 is completed, the steel sheet pile 7 is then built into the hardened material of the second hole 2. In this way, a steel sheet pile is placed in the hole one hole before the completion of drilling and injection, and an earth retaining wall is constructed continuously. In this case, it is also possible to perform the drilling and injection of the suspension several times in succession and then erect the steel sheet piles.

Figure 3 compares the unconfined compressive strength (hereinafter simply referred to as strength) of a combination of cement, hemihydrate gypsum (hereinafter referred to as gypsum), water, and clay and the cured product, and this is shown graphically. FIG. We compared bentonite, which has a fine particle size, and new clay and mino clay, which have coarse particle sizes (hereinafter collectively referred to as refined clay). In the case of a suspension of mixed gypsum and cement, hardening begins in a short period of time as shown in Figure 4, so it is necessary to delay the hardening in consideration of the time from the end of kneading to the completion of injection during construction.

By varying the amount of setting retarder added to the suspension shown in FIG. 3C, it is possible to adjust the onset of curing as shown in FIG.

Normally, suspensions injected into the borehole are suitable for suspensions b or C in Figure 5, but if higher strength is required or long-term strength is not required, use the suspension as shown in Figure 3 E or F according to the target strength. The formulation is slightly changed, and a suspension is used in which a set retarder is added in proportion to the amount of gypsum.

The reason why gypsum, cement, and purified clay are used in the present invention is that the initial strength, the time required to develop it, and the state of development of long-term strength can be varied depending on the combination of materials used. For example, in the case of bentonite and cement-based materials, the strength increases significantly over time, but in the case of gypsum and cement-based materials, the strength increases very slowly. In addition, it is desirable that the initial strength is about 2 to 3 kg/cm ² , but in the case of the gypsum or cement system of the present invention, it can be increased to 1 to 5 kg/cm 2 as shown in Fig. 5 by appropriately setting the amount of setting retarder added.
The required strength can be easily obtained within a range of about hours.

When bentonite is used, the fluidity of the curing agent suspension is extremely poor due to the swelling properties of bentonite, resulting in a lack of workability. If you increase the amount of water added to improve fluidity, the development of initial strength will be delayed.
As shown in A and B in Fig. 4, strength is developed only after about 10 hours, and after 24 hours, strength of about 2 kg/cm ² is obtained, but since the increase in strength after that is very large, it is difficult to build up steel sheet piles or Adjacent drilling time is limited to around 24 hours. As shown in Figure 4D, when a suspension of cement, gypsum, and bentonite is used, the initial strength develops quickly, but the increase in strength after 24 hours is also large, so the subsequent steel sheet pile erection work is carried out at 24 hours.
Limited within hours.

In the case of gypsum, cement, and refined clay, the initial strength develops quickly and the subsequent increase in strength is extremely slow, making the work of erecting steel sheet piles very easy. Furthermore, by adding an appropriate amount of a setting retarder, the timing of the start of setting can be controlled, thereby improving the workability of drilling and pouring work. In the case shown in Figure 4E, only gypsum is added as a hardening agent suspension to purified clay and water, and it can be seen that the initial strength can be obtained the earliest, and there is no increase in strength after that. .

According to the present invention, it is possible to perform drilling and injection at an adjacent position immediately after the completion of drilling and injection by the earth auger, and it is possible to erect steel sheet piles while following the work by the earth auger. Furthermore, even after several days have elapsed due to a delay in construction due to some reason, the hardening agent can easily be installed because the strength increase is small.

As described above, according to the present invention, steel sheet pile driving work can be carried out without vibration or noise, especially in areas with gravelly ground and underground water flow, eliminating construction pollution and eliminating construction costs that were conventionally extremely expensive. There is an advantage that earth retaining wall construction can be easily carried out under ground conditions that are considered to be difficult or impossible.

Furthermore, since clay is used in the present invention, which is inexpensive and easy to handle, it is possible to construct earth retaining walls at a very low cost and to improve workability.

[Brief explanation of the drawing]

Figures 1 and 2 are plan views showing the construction order in the earth retaining wall construction method, Figure 3 is a comparison diagram showing the blending ratio of substances constituting the hardening agent suspension and the strength over time;
FIG. 4 is a graph of FIG. 3, and FIG. 5 is a graph showing changes in uniaxial compressive strength depending on the amount of setting retarder in the hardening agent suspension. 1, 2, 3, 4, and 5 are holes, 6, 7, 8, and 9 are steel sheet piles, and 10 is a joint part.

Claims (1)

[Claims] 1. Drill a hole in the desired ground using an earth auger or the like to loosen the ground at the drilling location, and while pulling out the earth auger rod, inject a hardening agent suspension from the tip of the earth auger rod, and then pull out the auger rod to harden it. Replace the agent with soil, drill the next hole adjacent to the previously drilled hole with the earth auger in the same way, inject the hardener suspension when the earth auger rod is pulled out, and repeat this process to increase the hardener suspension. Form a series of holes into which the suspension is injected, and build an earth retaining wall into the ground by sequentially erecting desired steel sheet piles into these continuously formed holes into which the hardening agent suspension is injected. In the earth retaining wall construction method, by using a suspension of hemihydrate gypsum and natural or purified clay to which an appropriate amount of a setting retardant has been added, or a hardening agent suspension in which an appropriate amount of Portland cement is mixed, the hardening agent can be reduced. By arbitrarily setting the setting start time and slowing down the increase in strength over time after reaching the desired initial strength, the subsequent erection of steel sheet piles,
An earth retaining wall construction method that improves the workability of auger excavation and eliminates accompanying noise and vibration.