JP2763405B2 - Ground improvement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for improving soft ground.

[0002]

2. Description of the Related Art Conventionally, paper drain,
A construction method of placing a sand pile or the like is known. However, there is a demand for improvements in pile strength and material cost. By the way, a large amount of surplus soil is generated from construction sites and mines. For example, in the 21st century ten years later, it is expected that three prefectures around Tokyo will reach 7,700 m ³ .
Therefore, even today, disposal by landfill or the like cannot be dealt with alone, and treatment of residual soil has become a major social problem these days.

[0003]

As a result of repeated investigations to solve the above-mentioned problems, when the remaining soil and the like are used to be piled on soft ground under certain conditions, the pile strength is sufficient. It has been found that this leads to cost reduction and effective use of the surplus soil. The ground improvement method according to the present invention based on such knowledge is based on the premise that water such as surplus soil generated from construction, mining, etc. is dehydrated with soft-burning quicklime in advance, and hard-burning quicklime and, if necessary, cement on the dewatered surplus soil. ,
It is characterized in that a mixture formed by mixing at least one selected from a pozzolanic substance and gypsum is cast in a fixed arrangement in a pile on soft ground, and is softened on remaining soil generated from construction, mining, etc. Pour a mixture of calcined limes, hard-burned limes, and, if necessary, a mixture of cement, pozzolanic substances and one or more selected from gypsum in a fixed arrangement in a pile on soft ground. Characteristic ground improvement method.

[0004] In the present invention, the surplus soil and the like generated from construction, mining, etc. are concretely excavated surplus soil, mining waste material, concrete waste material, mine flushing mud, etc., having a particle size of 30 mm or less. Soft burnt limes are CaO, CaO.Mg.
CO ₃ , CaO.MgO, etc., which are fired at a general temperature of about 1000 ° C.

[0005] In the first method of the present invention, first, soft burnt lime is mixed with residual soil or the like in advance to dehydrate. Here, the mixing amount of the soft burnt lime may be an amount necessary for dehydrating water in the remaining soil. That is, it is a theoretical amount required for dehydrating the water in the residual soil by the digestive water absorption reaction of the soft-burned quicklime.
In the present invention, soft burnt lime is used primarily for dehydrating the water contained in the residual soil, etc., but secondarily, the pozzolanic reaction with the mixed residual soil and pozzolanic substances is performed. The pile is expected to be hardened by

[0006] Next, in the first method of the present invention, hard-burned quicklime and, if necessary, at least one selected from cements, pozzolan substances and gypsum are mixed with the dewatered remaining soil and the like. Here, the hard burned lime is limestone (CaCO 2).
₃ ), dolomite (CaCO.MgCO ₃ ) fired at a firing temperature of 1200 ° C. or more and a firing time of 1 hour or more. The cements include ordinary, early-strength, and moderate-heat Portland cements, blast furnaces, silica, and fly ash mixed cements, and alumina, ultra-rapid hardening, ultra-slow-effect, colloids, and ultrafine particles. The pozzolan substance refers to granulated blast furnace slag, converter slag, electric furnace sill, silica fume, artificial pozzolan such as fly ash, and natural pozzolan such as Kanto loam, shirasu, and tough. Further, gypsum includes anhydrous gypsum (CaSO ₄ ) and hemihydrate gypsum (CaSO ₄
* 1/2 H ₂ O) refers to gypsum dihydrate (CaSO ₄ .2H ₂ O).

[0007] On the other hand, the second method of the present invention is to mix soft-burning quicklime with remaining soil and the like, and at the same time, hard-burn quicklime and, if necessary, one or more selected from cements, pozzolan substances and gypsum. Etc. to obtain a mixture. In this case, the reactivity between the soft-burned quicklime and the hard-burnt quicklime is different, so that the same operation and effect as in the first method of separately mixing the soft-burned quicklime and the hard-burned quicklime in the remaining soil can be obtained. That is, the soft burnt lime firstly reacts with moisture in the remaining soil and the like to cause dehydration, and thereafter, the dehydrated remaining soil and the like and the hard burnt lime react.

In the present invention, by mixing dehydrated hard burnt lime, the digestion reaction can be temporarily delayed when it is placed on soft ground. That is, the reaction of the hard-burned quicklime with water is slower than that of the soft-burnt quicklime, so that the stability in the operation of piled into the soft ground having a high water content is ensured. On the other hand, after the casting, the latent hydraulic property becomes more apparent in the pile, which contributes to the strength development, and the hardening action by the pozzolanic reaction after the hydration reaction can be expected in the same manner as the soft burnt lime.

The preferred compounding ratio in the present invention is shown below. 15 to 85% by weight of dehydrated surplus soil 85 to 15% by weight of calcined quicklime Cement 0 to 20% by weight Pozzolanic substance 0 to 20% by weight Gypsum 0 to 10% by weight 15% by weight or more of dehydrated surplus soil is preferable. If the amount is less than this, the economic effect cannot be expected and the object of the present invention cannot be achieved. On the other hand, the reason why the amount is preferably 85% by weight or less is that if it is more than this, the pile strength is likely to be insufficient. Because. The reason why hard burnt limes are set in the above-mentioned range is also the same, and in this range, the action as described above is exhibited. It should be noted that cements, pozzolanic substances, and gypsum can be used without impairing the objects, functions and effects of the present invention as long as they are within the above-mentioned ranges.

According to the present invention, the mixture thus prepared is
The pile is cast in a fixed pattern on soft ground in a usual manner. Thereby, soft ground can be improved.
The soft ground in the present invention, in addition to the general soft ground,
It refers to the so-called sandy ground that may cause liquefaction.

The use of the remaining soil and the like as the pile material as described above in the present invention is intended not only for the purpose of effectively utilizing the remaining soil and obtaining an economic effect but also for expecting a pozzolan reaction between the remaining soil and the lime. is there. Further, when the remaining soil or the like is made of a pile material, the remaining soil or the like is filled in the voids in the pile and is closest packed, so that an effect that the expansion force of quick lime can be effectively applied to the consolidation of the intermediate ground is also exerted.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 Wet density generated at a construction site 1.5 t / m ³ , water content 60%
40 tons of soft-burned quick lime was added per 20 m ³ of excavated soil, mixed with a shovel, and allowed to stand for 2 hours until the digestion and absorption reaction was completed. After that, the mixture was remixed with a shovel and dewatered in mud, and was calcined in a rotary kiln at 1300 ° C. for 2 hours. The calcined calcined lime having a particle size of 30 to 5 mm, 12 tons, ordinary Portrad cement 2 tons, blast furnace water 2 tons, anhydrous 1 g of gypsum was charged and mixed with the same shovel for 15 minutes to produce a mixture of the present invention. Using the above mixture, 20 piles having a pile diameter of 50 cm and a length of 10 m were placed in a square arrangement with a pile pitch of 1.2 m on a sandy ground containing a silt with an N value of 12. One month after casting, the improvement effect was confirmed. The pile diameter had expanded to an average of 60 cm due to the digestive water absorption of quicklime, and the surrounding ground had been dewatered and consolidated at the same time. When the N value of the intermediate ground was measured,
Was obtained. Incidentally, it is said that the ground with an N value of 15 or more is not liquefied, and it is recognized that the intended target was achieved.

Example 2 A limestone excavation site has a particle size of 10 mm or less and a weight of 1.
6, with respect to water content of 25% crushed stone 15 m ^3, soft baking quicklime 2
0t, 20t of calcined quicklime having a particle size of 30 to 5mm, 3t of fast-strength Portrad cement, 2t of fly ash, and 2t of gypsum dihydrate were simultaneously poured in a rotary kiln at 1500 ° C for 4 hours, mixed with a shovel, and digested with water. The mixture was left for 1 hour and 30 minutes until the end of the reaction, and then remixed with a jovel to produce about 70 t of the mixture of the present invention. 90% water content,
Using the above mixture, 50 pieces were placed in a square arrangement with a pile diameter of 40 cm, a length of 8 m, and a pile pitch of 1.2 m on a silty clay ground having a cone index of qc = 7 kgf / cm ² . Casting 1
After confirming the improvement effect after a month, the pile diameter was determined by the digestive water absorption reaction of quicklime and the filling effect of limestone crushed stone, etc.
It expanded to an average of 50 cm, and the surrounding ground was dewatered and consolidated at the same time. Also, the cone index qc of the intermediate ground
Was improved to about 15 kgf / cm ^2, and it was recognized that the intended purpose could be achieved.

[0015]

As described above, according to the present invention, a mixture of hard burnt lime and the like mixed with a material obtained by dehydrating surplus soil and the like generated from construction and mining with soft burnt lime or the like, As a pile material, a mixture of quicklime and hard-burnt quicklime is used as a pile material, so that effective use of remaining soil and the like can be achieved. In addition, stable pouring can be performed and hardening by the pozzolanic reaction can be sufficiently expected. . Further, since the residual soil and the like are filled in the voids of the pile material in a close-packed manner, there is also an effect that the expansion force of quicklime can be effectively applied to the compaction of the intermediate ground.

Claims (2)

(57) [Claims] 1. Moisture of surplus soil and the like generated from construction, mining, etc. is previously dehydrated with soft-burning quicklime, and the dewatered remaining soil is selected from hard-burning quicklime and, if necessary, cements, pozzolan substances and gypsum. A ground improvement method characterized by placing a mixture obtained by mixing at least one kind with a soft ground in a pile at a fixed arrangement. 2. A mixture obtained by mixing soft-burned quicklimes, hard-burned quicklimes, and, if necessary, one or more selected from cements, pozzolanic substances and gypsum into remaining soil and the like generated from construction, mining, etc. A ground improvement method characterized by placing a pile in a fixed location on soft ground.