JPH06220834A - Improving method for heaved ground - Google Patents

Abstract

PURPOSE:To prevent the damage caused by the heaving of the ground due to aridity by crushing the ground surface, spraying water over the whole surface, drying it, then rolling it flat. CONSTITUTION:The cut earth ground is excavated to the specific depth below the ground surface with a ripper and the like. The excavation depth is set to about 1(m) as a standard. Rocks at the cut earth ground portion are crushed to the diameter of about 5-6cm, for example, and are efficiently brought into contact with air and water. Crushed rocks are again spread and rolled. Rocks are further crushed. Water is sprayed over the whole cut earth ground. The whole surface may be exposed to a rainfall. The cut earth ground is properly dried and rolled flat with a roller. The improved ground having more voids and gaps than the original cut earth ground is obtained. The occurrence of the ground stress due to the crystallization pressure of sulfate minerals causing the heaving can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the drying of cut grounds formed by sedimentary rocks of sandy and mudstones of the Mesozoic / latest Hakukai period, Cenozoic Tertiary and Quaternary Pleistocene. The present invention relates to a method for improving the ground that swells due to swelling.

[0002]

2. Description of the Related Art Conventionally, it is well known that bedrock containing a large amount of swelling minerals such as montmorillonite causes "swelling" by absorbing water.

However, a considerable part of the ground consisting of sedimentary rocks of sandy and mudstones of the Mesozoic-latest White Sakai period, Cenozoic Tertiary and Quaternary Pleistocene "swelling due to water absorption". On the contrary, it has recently become known in various places that it causes "a blister caused by drying".

However, in the past, the cause of the phenomenon of "plate swelling due to drying" has not yet been sufficiently investigated,
The current situation is that the measures have not been established yet.

[0005]

However, the swelling of the cut ground due to drying (hereinafter simply referred to as swelling) is caused by the fact that the ground is dried and swelling appears when a house or factory is built. The uplifting phenomenon caused by "bulging" causes damage to the houses and factories. Therefore, repairs, rebuilding, relocation, etc. are forced, and the cost of countermeasures after a problem occurs becomes enormous.

In view of such a point, the present invention is "disc swelling".
It is an object of the present invention to provide a method for improving the ground, thereby preventing the ground from expanding.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention digs up the ground surface portion of a cut ground that swells by drying and crushes it to an appropriate depth, and then water the entire surface. Is sprayed, dried and then rolled to flatten.

[0008]

As a result of earnest research, the present inventor has determined that "disc swelling" occurs due to the following causes. That is, between the surface of the ground (so-called ground surface) and several tens of meters below the ground, water that has rained, snowed, and soaked into the ground directly, and such water has a lateral vector. There is groundwater slowly flowing in the ground,
Since both of them have their origins in rainwater that has poured into the air from a high altitude, they are sufficiently dissolved with oxygen.

The water that contains oxygen and soaks underground reacts with various kinds of minerals that compose the ground while flowing through the ground and melts some mineral components. Put in. The mineral most likely to react with oxygen-containing groundwater is pyrite (FeS ₂ ).

Pyrite is most likely to be formed by the decomposition of iron bacteria under reducing conditions in the process of forming a stratum by depositing mud and sand on the shallow sea floor. In Japan, the Cenozoic Tertiary sandstone and mudstone layers contain pyrite, which is universally contained in a proportion of about several percent. In particular, pyrite content is extremely common in sandy and pelitic sedimentary rocks of the Tertiary to Quaternary period, in which a lime-subash layer in which plant material is carbonized under strongly reducing conditions intervenes.

Water that has infiltrated directly from the ground surface into the ground as rainwater or snow water or groundwater containing oxygen that has flowed in from the adjacent ground reacts with pyrite to produce sulfate radicals (SO ₄ ) as in chemical formula 1.
It becomes groundwater including.

[Chemical 1] Groundwater containing SO ₄ reacts with plagioclase, amphibolite, pyroxene, etc., which are the main minerals that make up the ground, and dissolves Ca, Na, Mg, etc. in these minerals.

In this way, SO ₄ , Ca, Na and Mg
When the surface layer of the ground becomes dry,
It slowly moves to the surface by capillary action through cracks in the ground and the gaps between mineral particles, and finally reaches near the surface.

SO ₄ · Ca · Na · M of such groundwater
The g concentration increases significantly due to evapotranspiration on the surface,
The following various sulfate minerals (hereinafter referred to as salts) crystallize along the surface of the ground and cracks and minute gaps in the ground (up to a depth of several cm to several tens of cm or several meters) near the surface of the earth Become. Gypsum CaSO ₄ .2H ₂ O Epsomite MgSO ₄ .7H ₂ O Tenardite Na ₂ SO ₄ Mirabilite Na ₂ SO ₄ .10H ₂ O Of these, gypsum is the most commonly formed salt mineral.

As the above-mentioned salt is condensed and filled in the cracks and fine gaps in the ground, stress due to the crystallization pressure of the salt is generated in the ground and the ground expands, so-called "ground "Blistering" occurs. In addition, the direct precipitation growth of the salt layer on the ground surface is also a major cause of the occurrence of "bed swelling".

However, when a portion having a predetermined depth on the surface of the ground is excavated as in the present invention, and the crushed rock fragments are spread again and compacted, the depth of the excavated portion below the surface is far deeper than the original stratum ground. It will have many voids and gaps. Therefore, when the surface layer of the ground is dried, SO ₄ · Ca · Na is added to such a porous portion (portion having a high porosity).
-Even if groundwater containing K / Mg rises, the salts deposited by evapotranspiration of water on the surface only fill these voids / gaps between rock masses formed by crushing, Stress due to crystallization pressure does not occur in the ground. or,
Direct crystallization of salts on the surface is unlikely to occur.

[0016] Further, by excavating and crushing and exposing to rain, or by spraying water, sulfate ions are diluted and run out, and the absolute amount of the influence (depth about 1 m) or absolute amount is reduced.

Furthermore, during excavation and crushing work, the chemical change is promoted by the wetness caused by rainfall and the dryness caused by solar radiation. Even if the residue causes a chemical change, the amount is very small and does not make you feel any damage.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 to 5 are explanatory views showing the steps of the embodiment of the present invention. FIG. 1 shows a cross section of a swollen cut ground (hereinafter, simply referred to as ground) 1. As shown in FIG. 2, the ground 1 is excavated by a ripper or the like to a predetermined depth below the surface of the earth.

This excavation depth may be about 1 meter as a standard, but this is determined by the topography. For example, the standard is a case where the terrain is approximately horizontal about 50 meters, and if the surrounding terrain is lower than the ground 1, and if the position of the building is close to the lower part, then 1
Meters are scarce and need more deeply. On the contrary, if there are high mountains around or on the back, groundwater will be replenished, so it may be shallower than 1 meter or may be untreated in some cases. In addition, when the span of a building is large, such as in a factory, it is necessary to increase the depth.

The rock 3 of the ground portion 2 excavated and excavated is crushed into fine pieces. As the particle size of this crushing,
The smaller the diameter, the higher the ratio of contact with air and water. The rock thus excavated and crushed is laid again and compressed as shown in FIG. The rock is further crushed by this compaction.

Next, the ground 4 which has been crushed and spread and compacted
As shown in FIG. 4, water is sprayed over the entire surface. This water application may be forced or it may be exposed to rainfall. The amount of water sprayed is about 10-3
An amount equivalent to 0 mm / hour of rainfall is sufficient.

Finally, the sprinkled soil 5 is appropriately dried and then flattened by compacting with a compactor (sheep roller, vibrating roller, tire roller, bulltozer) 7 as shown in FIG. 5 to complete the improved soil 6. .

FIG. 6 is an enlarged sectional view of a part of the completed improved ground 6. As can be understood from FIG. 6, the improved ground 6 has many voids and gaps.

[0024]

As described above, according to the present invention, far more voids and gaps are formed up to the deep part of the excavated portion of the surface of the earth as compared with the original stratum. Thus, the drying of the ground surface layer portion, even come such porous portions groundwater elaborate dissolved _{SO 4 · Ca · Na · K} · Mg (the high porosity portion) is increased, at the surface The salt precipitated by the evapotranspiration of water only fills these voids and gaps between the rock masses formed by crushing, and stress due to crystallization pressure does not occur in the ground. Also, direct crystallization of salts on the surface of the ground is unlikely to occur.

Further, by excavating and crushing and exposing to rain, or by spraying water, sulfate ions are diluted and flow out, and the absolute amount of the influence range (depth about 1 m) is extremely reduced.

Furthermore, during excavation and crushing work, the chemical change is promoted by the wetness caused by rainfall and the drying caused by solar radiation. Even if the residue causes a chemical change, the amount is very small and does not make you feel any damage.

Therefore, according to the ground improvement method of the present invention, it is possible to prevent the occurrence of swelling.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an example of the present invention.

FIG. 2 is a next process explanatory view showing the embodiment of the present invention.

FIG. 3 is an explanatory view of the next step showing the embodiment of the present invention.

FIG. 4 is an explanatory diagram of the next step showing the embodiment of the present invention.

FIG. 5 is an explanatory view of the next step showing the embodiment of the present invention.

FIG. 6 is a partially enlarged cross-sectional view of the improved ground.

[Explanation of symbols]

 1 Ground that swells 2 Ground that has been dug up 3 Rock 4 Rock that has been crushed and spread 5 Improved ground

Claims (1)

[Claims] 1. After digging the ground surface portion of the cut ground board that swells due to drying to an appropriate depth and crushing it, water is sprayed over the entire surface, and after it is dried, it is compacted to be flattened. A characteristic method for improving the swelling ground.