16）岩手県指定文化財吉田家住宅の再生をめざして－救出された部材の被災状況調査－

田家住宅復元が掲げられており、今後、救出した部材を用いた住宅の復元が行われる予定です。

岩手県指定文化財吉田家住宅の救出
吉田家住宅は、仙台藩領気仙郡の大肝入の住宅遺構で、享和２（1802）年に建設されました（図１）。仙台藩の大肝入は、村方役人の中でも最上位に位置する役職であり、地方の有力者が藩から任命されました。旧仙台領内におけるほとんどの大肝入住宅遺構がすでに失われている中で、当該住宅遺構は建設年代や大工棟梁名、藩政期における使用法の一部が明らかにされており、母屋以外の各種付属屋（土蔵、味噌蔵、納屋）も残されているなど、学術的にきわめて貴重とされ、平成18（2006）年に岩手県有形文化財として指定されました。
当住宅は建築後400年の間、11回に及ぶ津波や、洪水、大火を経験し、その都度それらを乗り越えてきましたが、平成23（2011）年３月11日に発生した東北地方太平洋沖地震による大津波によって主屋と各種付属屋が全て流失する等、壊滅的被害を受けました。座敷廻り部分は屋敷の裏側に、茅葺屋根は南西側に位置する諏訪神社を回った気仙小学校側に300mほど流されてしまいました。しかし、岩手県立博物館、八戸工業大学・月舘敏栄教授とその学生、所有者らによる懸命な部材の救出活動が行われ、同年6月中旬には主要構造部材の7割程度に相当する1016本の部材を救出することができました（図２）。陸前高田
市の復興計画の中にも、生涯学習拠点の設置としての吉救出された吉田家住宅建築部材の脱塩実験救出された部材は海水損したことにより、内部にまで汚泥や塩類が入り込んでいました。このような状態のまま乾燥し部材を再利用した場合、塩分が吸湿してカビが発生し、腐敗が進む危険性があります。そこで、部材に固着した汚泥の状況、塩類の含有状況、細菌の繁殖状況等を調査し、海水損の実態を明らかにした後、被災状況に応じた措置を講ずることとし、肉眼では判定が困難な塩類の含有状況、とりわけ塩化物イオンの含有状況を以下に述べる手順で調査しました。

16) For the Restoration of the Yoshida Family Residence, aDesignated Cultural Property of Iwate Prefecture -Surveyof a Damage to Salvaged Building Material-by the Iwate Prefectural Museum, Professor Toshiei Tsukidate
and his students at the Hachinohe Institute of Technology,
and the owner of the residence. By mid-June of that year,
1,016 building components which make up about 70 percentof the primary structural components were salvaged (Fig.2).
The restoration of the Yoshida Family Residence as a centerfor lifelong education is declared in the restoration project ofRikuzentakata City. Restoration of the residence using salvaged
structural material will soon begin.

Salvage of the Yoshida Family Residence, a cultural property
designated by Iwate Prefecture.
The Yoshida Family Residence is the remains of a residenceof an okimoiri (a village official) in the Kesen District of theformer territory of Sendai Clan, which was built in 1802 (Fig.1).
The okimoiri of the Sendai Clan was the highest position forvillage officers, appointed from local influential persons bythe clan. Most of the remains of okimoiri residences in theformer Sendai territory have already been lost. Therefore,
these residential remains are considered very valuable from anacademic perspective, because of the date of its construction,
the master carpenter’s name, some its usage during the clanadministration period is known, and because various types
of attached buildings in addition to the main building (astorehouse with thick earth walls, a miso warehouse, andadwelling) remained. It was designated as a tangible culturalproperty by Iwate Prefecture in 2006.
This residence has survived tsunamis, floods and fires eleventimes in the 400 years since it was built. However, all of themain building and attached buildings suffered devastating
damage: they were washed away by a tsunami caused by theGreat East Japan Earthquake on March 11, 2011. The guest
room was pushed to the back of the residence and the thatchedroof was carried about 300m to Kesen Elementary School
beyond the Suwa Shrine, which is located southwest of thebuilding. However, strenuous salvage activities were carried out

150

ア．調査用部材の選別
調査用部材を肉眼観察し、表面に相当量の土砂や泥が固着し、多量の塩分を含有すると推定される資料（図3a、
表１で保悪部材と記載）、表面に土砂や泥の固着は確認されず健全と判断される部材（図3b、表１で保良部材と記載）の２種類についてそれぞれ３本ずつ選別しました。
イ．選別した部材の記録
選別した部材について、以下の４項目の調査を実施しました。
①部材の重量測定（乾燥完了を判定するための乾燥重量）②外観形状写真撮影（脱塩実験後の形態変化を確認す

Desalination experiment using salvaged building material from theYoshida Family Residence
The salvaged building material contained sludge and a highsaline content, because of seawater damage. If the building
material was dried without processing and was reused, thesalt would absorb moisture and it could get moldy and rotten.
Therefore, it was decided that measures should be taken
according to the state of damage after the condition of sludge
affixed onto the building material,the salinity content, and thepropagation of bacteria was confirmed and the actual conditionof the damage from seawater was surveyed. Research was
carried out on the salinity content, in particular, the content ofchloride ions, which is difficult to determine with the nakedeye, by the following procedures.
A. Screening of building material for research
The building material to be researched was observed. The
material was screened for two things. First, items onto whicha substantial amount of dirt, sand, and mud was affixed andwhich were presumed to contain a large amount of salts (Fig.3a,第4章

安定化処理と修理

表1 建築部材脱塩の推移
Table 1 Desalination process on building material
水道水
水道水
塩化物イオン濃度
塩化物イオン濃度（保悪部材脱塩時）（保良部材脱塩時）
Chloride ion concentration in Chloride ion concentration in
tap water
tap water(in desalination of material in (in desalination of material inpoor preservation)
good preservation)
（ppm）
（ppm）

脱塩日数
Day ofdesalination

保悪部材
Material inpoor
condition
（ppm）

保良部材
Material ingoodcondition
（ppm）

脱塩1日目
Day 1

6.64

3.33

2.49

2.67

6.05

0.97

脱塩2日目
Day 2

9.94

3.86

2.48

2.47

10.9

2.03

脱塩3日目
Day 3

7.88

3.02

2.16

2.32

8.33

1.02

7.02

3.04

2.39

2.20

6.75

1.22

6.41

5.86

2.54

2.65

5.65

4.68

4.65

4.75

1.99

2.89

3.87

2.71

41.54

12.63

脱塩4日目
Day 4
脱塩5日目
Day 5
脱塩6日目
Day 6
計
Total

溶出した塩化物（g）
Chloride elution
volume (g)

注1）水槽水量は1,458L。 Note 1) The amount of water in the tank is 1,458 l.

図1

震災以前の吉田家住宅（母屋）東北工業大学 高橋恒夫氏提供
Fig. 1 The Yoshida Family Residence (main building)
before the earthquake
Provided by Prof. Tsuneo Takahashi of the Tohoku
Institute of Technology

図2 回収した部材
Fig. 2 Collected building material151

るため、六面全てを記録）③形状記録（反り等脱塩後の形状変化の有無を確認するため）④樹種同定用の木屑サンプリング（樹種の違いと塩分含有量を確認するため）
ウ．部材の洗浄・脱塩洗浄・脱塩手順は以下のとおりです。
①部材表面を高圧洗浄機（精和産業株式会社）で丁寧に洗浄し、表面に固着する土砂や泥を可能な限り除去する②水槽に約1,500ℓの水道水を入れ、部材を水槽底面にロープで固定し、完全に浸漬する（図４）③水槽内の水を撹拌し、部材から溶出した塩化物イオンが水槽内に均一になるよう、水槽の２箇所にポンプを設置する（図５）④部材浸漬後、24時間ごとに部材を引き上げ、部材から滴る水を採水する。また、水槽の中心と右上端および左下端に採水ポイントを設け、各々表層、中層、底層の計３か所から約100mlの脱塩液を採取する。
エ．
採水終了後、水槽の水を全て交換し水槽内を掃除した
後、水槽に新しい水道水約1,500ℓを入れる
オ．

referred to as building material in poor condition in Table 1). In
addition, material which was judged to be sound with no dirt,sand, and mud affixed onto its surface (Fig.3b, referred to as
well preserved building material in Table 1).
B. Records of the screened building material
Concerning the screened building material, the following
four things were measured.    (1) Weighing of the building material (measuring their dry
weight to confirm the completion of drying)    (2) Taking photographs of their external shapes (recording
all six sides to confirm changes in shape after thedesalination process)    (3) R ecording their shapes (for confirming whether
there are changes in shape including warping afterdesalination)    (4) C hip sampling for identifying tree species (forconfirming the difference between tree species andtheir salinity concentration)
C.Washing and desalination of building material
The washing and desalination procedures were as follows.    (1) Wash the surface of the material carefully using ahigh-pressure washer (manufactured by Seiwa SprayPump Inc.) to remove as much, dirt, sand, and mud on
the surfaces as possible.    (2) Put 1,500 L tap water in a tank and attach the building
material to the bottom of the tank to immerse it
completely (Fig.4).
    (3) Stir water in the tank and set pumps at two points in152

ハンディ塩素イオンメータ（TiN-5102i型、東興化学研究所製）を用い、採水した脱塩液に含まれる塩化物イオン濃度の測定を実施する（図６）。
カ．
脱塩終了後、仮設陸前高田市立博物館の被災資料乾燥庫を借り、部材重量が脱塩実験前の重量に戻るまで乾燥を行う
部材の脱塩結果
脱塩は木材から滴る水の塩化物イオン濃度の値が５ppm未満になるまで継続しました。表１は脱塩実験結果です。保存状態の良好な部材では、脱塩開始の翌日には５ppm未満になりましたが、保存状態の劣悪な部材は当該濃度に達するのに６日を要しました。表によると、溶出塩化物イオン濃度に増減がみられますが、これは木材の内部に浸透した塩分が徐々に溶出したことに起因すると考えられます。また、保存状態が良好な部材からは６日間で総量約13gの塩化物イオンが、保存状態が劣悪な部材からは総量約42gの塩化物イオンが溶出しました。
海水損した建築部材の脱塩は前例がありません。今回の実験によって含有が確認された塩化物イオンが部材の劣化進行に深刻な影響を及ぼすかどうか、この点についての見極めが必要です。また、脱塩終了後の部材にどの程度の塩化物イオンが残っているかも確認しなければなりません。今後更なる実験を実施し、これらの点を明確にしたうえで、部材の安定化処理方法を構築していく予

the tank so that the amount of chloride ions flowing out
from the building material will be even (Fig.5).
    (4) After the building material is immersed, it is taken outof the tank every 24 hours and the water dripping fromit was collected. In addition, water sampling points
were set at the center, the upper right and the lower leftof the tank, and about 100 ml of desalinated water was
sampled at those three points (top layer, middle layer,
and bottom layer) respectively.
D. After water sampling, all the water in the tank was replaced
and the tank was cleaned. After that, about 1,500 L of fresh
tap water was pumped into the tank.
E. U se a Handy Chloride Ion Meter (TiN-5102i type,manufactured by Toko Kagaku Kenkyusho) to measure thechloride ion concentration contained in the desalinated water(Fig.6).
F. After desalination, we used a dry warehouse to store damaged
items of the temporary Rikuzentakata City Museum andcontinued to dry the building material there until their weight
returned to what it was before the experiment.
The results of desalination of building material
Desalination continued until the level of chloride ion
concentration in the water dripping from the lumber decreased
to less than 5 ppm. Table 1 shows the results of the desalination
experiment. The chloride ion concentration of the building
material in good condition decreased to less than 5 ppm theday after the desalination started. However, it took six days forthe building material in poor condition to reach the appropriate

第4章
定です。
浅川崇典（陸前高田市教育委員会）
熊谷賢（陸前高田市立博物館）
赤沼英男（岩手県立博物館）

安定化処理と修理

concentration level. According to the table, there were increasesand decreases in eluted chloride ion concentration. It isthought that this is because salts contained in the lumber eluted
gradually. In addition, about 13 g of chloride ions was eluted
from the building material in good condition, while about 42 g
was eluted from the building material in poor condition during
the six days.
There are no previous precedents of desalination of seadamaged building material. It is necessary to confirm if thechloride ions which were identified by this experiment would
have a serious impact on the deterioration of the building
material. Also, it is necessary to confirm to what extent chloride
ions remain in the building material after desalination. These
points will be clarified by carrying out more experiments, andthen proper stabilizing processes on building material will be
developed.

Takanori Asakawa (Rikuzentakata City Board of Education)
Masaru Kumagi (Rikuzentakata City Museum)
Hideo Akanuma (Iwate Prefectural Museum)

図3a 保悪部材
Fig. 3a Building material in poor condition

図3b 保良部材
Fig. 3b Building material in good condition

図4 部材脱塩実験
Fig. 4 Desalination process on building material

図5 水槽内に設置した水中ポンプ
Fig. 5 A submersible pump placed in the tank

図6 塩化物イオン濃度計測に用いた機材
Fig. 6 A device used to measure chloride ion concentration

153