JPS6225807B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an improvement method for ultra-soft ground, first of all,
The present invention relates to a composite pile construction method in which a base is formed to make a good ground, and then a quicklime pile is used to improve the ground to be good enough to prevent consolidation settlement and ground collapse due to subsequent overloading.

[Prior art and problems]

Ultra-soft ground consisting of peat and sludge layers has extremely weak ground strength, depending on the soil characteristics of the special soil, and has an extremely high water content, as well as a large amount of organic matter and almost no inorganic soil particles. Even if there is, there is an extreme lack of it, so the soil itself has a weak structure. Therefore, the improvement of these ultra-soft grounds is more difficult than that of soft ground made of cohesive soil, and no reliable and reliable improvement method has yet been provided. Most of the conventional methods for improving soft ground are classified into methods for promoting consolidation and methods for preventing subsidence through consolidation.
As an example, it is a well-known fact that when using the sand pile construction method, the soil improvement effect cannot be expected unless the pile is reliably built into the ground, and when it is used on extremely soft ground, no improvement effect can be expected. be.

[Means to solve the problem]

The present invention can economically obtain reliable ground improvement effects that cannot be seen with these conventional construction methods, and can be applied to cohesive soil, sandy soil, dry soil, etc. in ultra-soft ground.
After pouring soil, sand, or similar materials made of lime or inorganic industrial waste or a mixture of two or more of these into a pile, the soil is thoroughly mixed with the ground soil to be poured. , is characterized by forming quicklime piles on good ground after forming a base for reinforcement.

[Effect]

Therefore, soil, sand, and other similar materials are poured in piles and mixed throughout the ground to make the strength uniform and at the same time form a base for strengthening the ground. After this, a quicklime pile is cast (this point differs from the conventional sand pile casting), and this quicklime pile causes rapid consolidation and expansion during digestion, which eliminates the problem of long-term consolidation settlement due to overloading. The ground properties themselves are changed to a ground that does not

【Example】

The details of one embodiment of the present invention will be explained below.
First, in order to compensate for the lack of inorganic soil particles, which is a characteristic of ultra-soft ground, materials similar to soil, sand, etc., corresponding to the missing soil particles, such as clayey soil, dry soil, limestone, or One or a mixture of two or more of these inorganic industrial wastes is poured into ultra-soft ground using conventional equipment in the form of piles at arbitrary intervals and depths depending on the improvement area and depth, and After forming a base for forming a good ground by mixing the whole with soil, that is, after consolidation settlement due to water absorption of the pile of soil, sand, etc. is completed, in the second step, the quicklime pile is mixed with the soil, sand, etc. The piles are placed at approximately the same depth at approximately the middle of each pile placement point, and rapid consolidation is performed to eliminate the properties of the soft ground itself. The above-mentioned inorganic industrial wastes include slaked lime, which is a waste product in the carbide manufacturing process, and slag, which is a waste product in iron manufacturing methods. When using these industrial wastes, it is particularly preferable to mix them with the other materials mentioned above, such as clayey soil, and to grind them to an appropriate particle size. Before placing quicklime piles, determine the amount of piles to be poured, such as soil or sand, in order to create a good base for the ground. It is also possible to aim for a level equal to or higher than that of ordinary soft ground. When piles of soil, sand, etc. are placed in this way, sandy soil itself has a lower water absorption effect than clay soil, so there may be a temporary decrease in ground strength and ground subsidence; The quicklime pile can sufficiently recover and increase the ground strength. As a substitute for the initial pile of soil, sand, etc. for the purpose of creating a good base, it is also possible to use quicklime or slaked lime used in the tests of the present invention described later. In this case, the aforementioned soil ,
Although it can achieve a greater improvement effect than piles made of sand, etc., in view of the ultra-soft ground that lacks soil particles, sand has a better particle size composition than piles made of slaked lime, etc., which generally have fine particles. It is better to use quality soil, and if a large amount of quicklime is used, for example, piles made only of quicklime have disadvantages such as excessive ground upheaval, and are economically unsuitable because they increase construction costs. Next, the improvement effect of the method of the present invention will be explained based on the test results shown in Table 1. In the test, soil adjusted to an initial moisture content of 100% and QC = 0.2 to 0.4 Kg/ ^cm2 was placed in a container measuring 40 cm long, 40 cm wide, and 50 cm deep to form ultra-soft ground for the test.
48mm piles were installed using the press-fit method. In this test, slaked lime piles were used as a substitute for piles of soil, sand, etc., which were used to form a good foundation. The order of placing piles is to first place a slaked lime pile as a substitute for piles of soil, sand, etc., and then, when the consolidation settlement due to water absorption of the slaked lime pile is completed, then to place each of the above-mentioned slaked ash piles. We investigated the improvement effect by placing quicklime piles in the middle of the points. The number and spacing of each pile are as follows.

[Test 1] Total of 18 piles, 9 internally slaked lime piles
Books were placed at intervals of 15 cm, and nine quicklime piles were placed at intermediate positions between the slaked lime pile placement points. Also,

[Test 2] Total of 25 piles, 13 internally slaked lime piles
The books were placed at an interval of 8 cm, and then 12 quicklime piles were placed.

As in [Test 1], the slaked lime piles were cast at the middle position of each of the slaked lime piles. moreover,

[Test 3] Only quicklime piles are placed at intervals of 10 cm and 16
We also investigated the improvement effect in the case of actual pouring.

【table】

【table】

【table】 Referring to the test results in Table 1,

[1],

[2] In either case, the initial ground strength of qc=0.3Kg/ ^cm2 is
By placing the first slaked lime pile as a substitute for piles made of earth, sand, or similar materials, qc=
The strength increased to more than 1.0Kg/ ^cm2 , which is comparable to that of ordinary soft ground made of cohesive soil, so it is considered that the base material will be good after the improvement by the first pile driving. It is considered that the purpose of forming the Next, looking at the effects of placing the second quicklime pile,

[Test 1] If the total number of piles is 18, the ground strength is 7Kg/ ^cm2 or more, and the total number of piles is 25.

[Test 2]
The ground strength is 10Kg/ ^cm2 or more. Judging from this result, it can be said that the soft ground has already been lost and has been improved to a good ground with great strength. Furthermore, the strength of each pile that was placed was comparable to the strength of the ground after the improvement. According to the construction method of the present invention, it is not the case that the improvement effect cannot be expected unless the pile is reliably created, as is the case with conventional construction methods, and it has been confirmed that a sufficient improvement effect can be obtained even if the pile itself is interrupted. Barefoot,
As mentioned above, when using the press-in method as in this test, even if you try to avoid mixing with the test ground soil as much as possible, the slaked lime pile and the ground soil will often be mixed at the bottom of the pile. Nevertheless, as seen from the test results, there was little decrease in the strength of the ground due to the mixing of the above-mentioned ground soil and slaked lime pile, and on the contrary, there was a tendency for the strength to increase. As mentioned above, after the first pile (slaked lime pile in the test) was placed, a temporary decrease in ground strength and ground subsidence occurred, and this decrease in ground strength was caused by soil, sand, and other similar materials. When the pile consisting of the ground is mixed with the ground soil, it becomes noticeable by stirring and mixing. Therefore, effective ground improvement effects can be obtained by mixing ground soil and piles after considering the ground properties and the type of piles. In other words, if the strength of the pile made of similar materials such as soil or sand is extremely lower than the strength of the ground after the pile is placed, the pile and the ground soil should be mixed using a known construction machine. By doing so, a ground improvement effect with uniform strength can be obtained. In any case, the temporary decrease in ground strength can be sufficiently recovered and strengthened by the quicklime piles placed afterwards.

Only 16 quicklime piles in [Test 3]

A comparative study of the ground improvement effect in the case of 18 composite piles in [Test 1] shows that the economical composite pile has a slightly better effect (7.0:6.5 in terms of soil strength), but a better effect can be obtained. . Table 2 shows the results of a comparative test between when the ground soil and piles such as earth and sand are mixed and when they are not.As is clear from Table 2, when the above ground soil and piles such as earth and sand are mixed entirely. After the reaction of placing quicklime piles, a better and stronger ground can be obtained than when no mixture is used.

【effect】

As described above, according to the construction method of the present invention, it is possible to improve the ground into a good, strong ground by eliminating the properties of ultra-soft ground itself, using economical and conventional equipment by using industrial waste, etc. It is possible to improve soft sand layers and to improve ordinary soft ground by appropriately reducing the amount of composite piles, and it can also be applied to conventional methods where the improvement effect is impaired due to discontinuation of the poured piles. However, even if the pile itself is interrupted, the method of the present invention eliminates the problem of long-term consolidation settlement due to the overburden load after the pile is placed due to rapid consolidation and the expansion force of the quicklime pile during digestion. It has a variety of effects, including the ability to quickly and reliably improve the ground.

[Brief explanation of the drawing]

The figure is an explanatory diagram showing an example of the construction method of the present invention.
FIG. 1 is a plan view, and FIG. 2 is a sectional view taken along the line shown in FIG. 1. 1...Ultra-soft ground, 2...Piles made of earth, sand, and similar materials, 3...Quicklime piles.

Claims (1)

[Claims] 1. Cohesive soil, sandy soil, dry soil, limestone, or inorganic industrial waste is deposited in ultra-soft ground consisting of a peat layer, sludge layer, etc., which has an extremely high water content and a lack of inorganic soil particles. After pouring soil, sand, or similar materials made of one or a mixture of two or more of these into a pile, it is mixed with the ground soil to be poured to strengthen the soil into a good condition. A method for improving ultra-soft ground by forming quicklime piles after forming the base.