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Types of masonry
One can separate the stone stacking methods into three categories; nozura-zumi ("weathered stone" stacking. There is minimal fabrication of the stone used in the wall), uchikomi-hagi (more work is put to each stone, resulting in a tighter fit), and kirikomi-hagi (each stone is meticulously worked and the result is perfect fitting stone wall).
The construction methods used differ not depending on the region but on the year in which it was built.
Nozura-zumi (Anoushu-zumi)
(Kamakura period-early Warring States period)
How to stack large and small natural stones. Fill the gaps between large stones with smaller stones (stitched stones).
Representative example Takeda Castle (Asago City, Hyogo Prefecture)
Azuchi Castle (Omihachiman City, Shiga Prefecture)
uchikomi-hagi
Warring States period-Battle of Sekigahara
A stacking method that reduces gaps by scraping the joints of stones. (Before Sekigahara)
Representative example Kumamoto Castle
Matsuyama Castle (Matsuyama City, Ehime Prefecture)
kirikomi-hagi
After the Battle of Sekigahara
How to stack stones by processing them linearly to eliminate gaps (after Sekigahara)
Representative example Edo Castle
Osaka castle
Characteristics of Anoushu stone stacking
The Anoushu stone stacking is representative of the nozura-zumi. It might look crude at first glance, but its robustness is unparalleled.
Because it is a characteristic of Anoushu-zumi masonry that natural stones are piled up naturally.
No stones of the same size, shape and weight
Stone surface (tsura), stone grain (direction in which stones are easily broken)
From things such as the top and bottom of the stone and the weathering of the stone
Because you have to pile up while checking the condition of the stones each time
It has been handed down only by oral tradition, not in written form or form.
At first glance, the field area looks crude, but the robustness is unmatched.
I will introduce the secret of robustness.
The secret of strength
~why it is strong ~
The secret of robustness is inside the stone
It might look crude at first glance, but its robustness is unparalleled. Its secret lays in where the weight of the stone rest. The weight of the stone is designed to rest about 1/3 of the depth from the surface of the stone wall and also, to prevent water damage, there is a layer of large gravel (fist sized) before the smaller gravel, this helps with the drainage of the water. It is in these out of sight parts that the secret handed down to Anoushu resides, and that in turn gives the robustness for a wall to stand the elements for centuries.
To hear the voice of the stone and to be guided by stone is our job.
We go to the stone pile and, for a day or two, walk around and around the stones, committing to memory each stone's personality. Then, drawing a mental image, we start placing the stones in our head. So, by the time the real stone stacking starts, there is already a complete blueprint in our minds. It will be more accurate to say that we converse and listen to the stone, rather than just telling them apart. As you work with the stone for a long period of time, it starts to teach you. The Anoushu skills were all handed down verbally, but, that is not because it is a mystery, but rather because it cannot be expressed in letters.
Analyzing the secret technique of Anoushu stone stacking
~ Is it really strong ~
Visiting the old to learn the new.
The analyzed data that proved the traditional technique.
Although the Anoushu stone stacking method has proven its robustness through its long history, to be applicable to the modern architectural standards, empirical data was needed. Therefore, an experiment was conducted where an Anoushu retaining wall was built next to a concrete block retaining wall, and then earth pressure was applied to them to measure displacement.
The standard for maximum load was 250 ton. To create a more sever condition, a weight of a jumbo jet, which will never happen in reality, was applied.
Experiment on the Shin-Meishin Expressway
Stronger than concrete?
Soon after the experiment was started, the retaining wall built by the Anoushu started to make unfamiliar crackling noises. The stone wall, in sections, had as much as 13 cm displacement, but, it withstood the entire 250-ton pressure. On the other hand, the concrete block retaining wall only had 5.5 cm displacement, however, when the pressure reached around 200 ton, the 30cm thick cast concrete made a loud busting sound and it failed. Although the displacement of the stone wall was larger, this experiment affirmed that it had a superior load bearing capacity than the concrete block wall.
The "flexible" load bearing capacity confirmed through state-of-the-art technology
A simulation called discontinuous deformation analysis, ran by the group led by professor Yuzo Onishi, from Kyoto University graduate program, made clear the structural characteristics of Anoushu style stone stacking. Anoushu style stone stacking structural drawing The simulation faithfully recreated the model of the stone wall structure under pressure. The result perfectly matched the certification test result. Then, another simulation was ran using the seismic data of Hanshin-Awaji class earthquake. The result showed that, again, there was a large displacement, but, it provided an excellent data showing that because of its displacement, the stones tightened and did not lead to its collapse and ceasing of retaining function.
