預制工藝

馬爾科·索爾

司馬蕾 譯

預制工藝

馬爾科·索爾

司馬蕾 譯

節選自馬丁·勞奇的《優雅的泥土——夯土建筑與設計》， 奧托·卡普芬格和馬爾科·索爾（編著），細部出版社，慕尼黑，2015年， 第118-121頁。由細部出版社再版。

預制工藝為夯土建筑提供了一種新范式，這種技術無論從定性還是定量的角度來說都是一次巨大的飛躍。它讓夯土建筑的建造達到了一個新水平，也讓更多的項目可以考慮使用夯土。這種分離建筑的生產和安裝過程的做法更為經濟，因為在施工現場的作業中，相比雇傭一群工人在現場夯土、慢慢地壘起建筑的做法，起重機能夠在工期很緊的情況下很快地把成品部件搭建好。因為部件在造好時已經是干的了，整合分包出去的各項工種時可以做到無縫銜接，這也大大地縮短了建造所需的時間。雖然生產這些墻仍然是一項時間密集型的工作，但生產和安裝的時間變得更容易規劃和協調了。

因為過去幾乎沒有離開現場在別處進行夯土的先例，夯土建筑中的預制工藝幾乎是個未知的領域，但現在已經開始出現了這方面的嘗試。相關的技術和結構要求變得更為細致，并開始通過優化設計來探索解決方案。在這座最初的預制夯土建筑的大體部分基本完工之后，后續的修整的工作也進化了很多，這讓由各種部件組成的墻體看上去就和在現場建造的夯土墻一模一樣。

但施工過程的規劃仍需要繼續進行改進，例如在工程的初期階段，盡管很難，仍要快速明確對這些夯土部件的要求。這涉及到施工的管理和生產間的密切配合，而其中對預制影響最大的要素是制造和沖壓的工藝。例如，在決定了墻的厚度之后，下一步要做的是調整部件的尺度以適應不同的空間高度。而部件的長度還要考慮到把部件搬送就位的起重機的荷載限制，這一長度是由起重機允許的最大重量、墻的高度和寬度共同決定的。這種在規劃和生產的交接中會出現的交互問題都需要仔細地進行評估。

為了盡量控制部件的數量以實現較低的造價和較短的工期，甚至連起重機的擺放位置、根據機械臂外展距離確定的最大負荷都需要進行考慮：靠起重機近的部件可以相對重些，也可以設計的長一些。位于森帕赫的瑞士鳥類研究所的項目就仔細地評估了這些方面的要素。

但同時，這也讓建造的技術也變得簡單多了：預制部件的細部都是標準化的，即使非熟練工人也可以來施工。建造工作也可以分配給多個實施方來分擔，這對夯土建筑行業整體也是有益的。

生產優勢

世界上第一個預制夯土部件是在1997年由Lehm Ton Erde Baukunst GmbHi設計的一面起居室里的墻。這面墻被安裝在木結構的建筑中，乍看之下在施工上幾乎不可能實現： 屋架的建造工期有限，進度很緊，此外，工程計劃在一月份進行，這個時期因為霜凍的關系不可能在場地上進行夯土。因此才出現了想通過起重機在建造木構架的同時把夯土墻吊裝進去的解決方案，也催化了土質建材的預制化進程。

這一時期的第一個大規模項目是古格勒打印機公司位于奧地利皮拉赫的一個辦公樓項目。項目中構成建筑內墻的標準化的部件被互相堆疊在一起，再把節點連接起來。這一墻體部件里包含了用地源熱泵供能的通風管道，夯土墻的功能則類似于地暖，利用其觸感特點，創造出舒適的室內環境。

制造古格勒項目中所需的160個部件花了3個月時間，但之后將其安裝到位只花了不到兩周時間。最新采用了預制夯土部件的項目則是位于瑞典勞芬的利口樂草藥中心項目和位于森帕赫的瑞士鳥類研究所項目。由于改良了制造流程，現在的部件生產速度比1990年代有了提升，生產和安裝部件所需的時間比大約為3:1。

1 機械預制能減少勞動力的需求，并加快了生產過程。這臺機器由Lehm Ton Erde Baukunst GmbHi研發/Mechanical prefabrication alleviates physically strenuous labor and expedites the production process. The machine was developed by Lehm Ton Erde.

Excerpt of Martin Rauch Refined Earth -Construction and design with Rammed Earth, Otto Kapfinger and Marko Sauer (eds.), Edition detail, Munich 2015, p. 118 - 121.

Reprint by courtesy of Edition detail, Munich.

2 由于墻體部件不抗拉，必須開發懸掛系統來進行裝吊。這種系統也能讓部件實現垂直放置/As the elements cannot be subjected to tensile loading, a suspension system had to be developed. This also allows the elements to be set in place vertically.

Prefabrication represents a new paradigm in rammed earth construction, as it is a quantum leap both in a quantitative and in a qualitative sense. It takes the practice to a new level and gives more options for finding projects that can be executed with rammed earth. Economic considerations support the argument for separating the processes of production and installation, primarily due to on-site logistics: rather than employing a team of laborers to ram the earth in situ, gradually putting up the building over time, cranes can quickly mount the finished elements in accordance with the demands of a tight schedule. As the elements are already dry when they are erected, integrating the remaining building trades of other subcontractors is seamless, which significantly shortens the duration of the construction work. Fabricating the walls is still just as time intensive a process, but the production and mounting phases can be more easily planned and coordinated.

As there are virtually no historical precedents for earth being rammed offsite rather than in situ, prefabrication in earth construction is largely unexplored territory, although experience is now beginning to emerge in this field. Its technical and structural requirements are becoming more refined - as are the solutions in matters of design. While the rudimentary joints of the first prefabricated buildings were roughly finished, retouching has become considerably more advanced, such that walls made up of compound elements are as homogeneous in appearance as walls rammed on site.

Improvements needed to be made in the planning process, as defining the earth elements requires hard and fast decisions to be made at an early stage. This involves a close collaboration between construction documentation and production, as often factors only tangentially related to the manufacturing and ramming process can be crucial to their fabrication. For example, once the wall thickness has been decided, the next step is to adjust the size of the elements to match the room height. The length is dependent on the load limitation of the crane that lifts the elements into place. Thus, the length is a product of the maximum permissible for weight, height, and wall width. These interdependencies, at the interface between planning and production, must be carefully evaluated.

In order to limit the number of elements as much as possible, which in the end results in a lower price and a shorter construction schedule, even details such as the location of the crane and the maximum load capacity relative to its outreach are considered: elements nearer to the crane can be proportionally heavier and therefore longer in design. In constructing the Swiss Ornithological Institute in Sempach, strict attention was paid to each of these aspects.

In contrast, technical implementation has become much simpler: prefabricated details are standardized and can even be put in practice by unskilled labor. The task can be dispensed to multiple actors, which is of overall benefit to the earth building trade.

Production Advantages

The first prefabricated element completed by Lehm Ton Erde was a living room wall in 1997. It was to be installed in a timber-frame construction, which at first appeared to be logistically impossible: the schedule of the framing was extremely tight in a fixed window of time, and, moreover, planned for January, when the earth could not be stamped onsite due to frost. A solution was thus sought that would allow the wall to be installed with a crane simultaneously with the timber construction process. This was the catalyst for prefabrication.

The first larger-scale project from this period was an office building for Gugler Printers in Pielach. The standardized elements, which were also interior walls, were stacked on top of one another and the joints then sealed. The modules contain flues for ventilation powered by a geothermal heat

使用預制材料來進行建造的項目數量也有了顯著的增長：預制墻體可以快速地進行生產而不用考慮天氣情況，這讓工程進度的調整變得容易多了。此外，現在的成品運輸也變得更容易了，這也有利于推廣室內預制工藝。即使是采用本地材料來進行建造的需求也可以被滿足，例如位于勞芬的草藥中心項目使用的土就是基地本身的土方，生產預制品的工廠距離工地還不到3km。對這種大型項目來說，在當地直接設工廠往往更為經濟，既可以利用當地的材料，也能減少運輸的距離。

機械預制

正如上文所說，夯土建筑的預制領域基本是片處女地，為了發展預制的工藝、進一步提高其生產效率，也應需求出現了一些新的發明。在工藝上的改進主要體現在減少生產部件所需的人力。而人力勞動中最艱苦的部分就是用原材料填滿模具并把填料壓實。

為此，馬丁發明了一臺機器，專門用來把土自動分配到模具里，再用一個運動的錘子來夯實它（圖1）。這一工作還是需要不少人力來參與，但這個送料機已經能完成其中的大部分工作了。因為已經不需要讓一個人來站在模具里面夯土，這種機器也能用來直接生產比較薄的墻體。此外，也能使用比較長的模具，通過一片片地連續堆疊水平土層來生產整面墻體，之后根據需要的尺寸把墻體切割開，再在現場按同一順序安裝起來。

懸掛和運輸

因為夯土部件的抗拉能力很弱，就像沒法從兩頭提起沒有加固過的土一樣，在安裝過程中，底面上的受力必須要非常均勻。對于較為輕薄的部件，通過加設木梁和幾條捆帶能幫助分散重量。但是對更大和更重的部件來說，就需要訂制開發專業的機械運輸系統，以便在放置它時實現3個維度上的同時調整。為了從下方托住部件，沖壓制造墻體的第一層時在墻底加裝了由圓形的管道和鋼筋構成的階梯狀構件。安裝時在管道下面鋪設錨桿，再用兩個鋼片把它安裝到吊升用的齒輪上去（圖2）。采用這樣的輔助工藝的缺點是在部件安裝完后，金屬件會露出來一部分。為了減少工藝的復雜性，也減少材料的浪費，這種鋼質構件現在已經用木楔來代替了。木楔在制造墻體時先嵌入其中，脫模時則可以拆除掉。這樣，楔子形成的孔洞就可以讓吊裝用的捆帶直接綁在部件上了。

墻體部件通過每隔60cm的捆帶固定到梁上，體塊和梁間的繩索系統能幫助荷載分布均勻，之后再通過兩個吊鏈讓墻體豎立起來（圖3）。

安裝過程

墻體部件被放在由純粘土砂漿構成的約1cm厚的墊層上。部件之間利用自身重量通過摩擦粘合，上部的部件會嵌入到砂漿中去。連接面四周的粘土砂漿必須涌出來，這樣才能保證砂漿包裹住了整個面。在部件正確地放置到砂漿上了之后，要用木楔子把它的位置固定住。在砂漿干燥之后，整個部件的重量會傳導到下部的部件上。因為夯土不能承受拉力，這一步驟對于夯土部件來說比對鋼筋混凝土部件重要得多。

各個部件之間的連接件和節點都會在裝配時或者完工之后再次封實。然而準備的工作在生產部件的時候就開始了：各個面的垂直角和水平的向上面上都已經切開了槽口，在裝配完工之后，這些槽口以最小1cm左右的間隙被填入石灰砂漿。因為石灰比土硬，并且和土的形變特性不同，要先在槽的底部墊一層軟粘土。當石灰塊變硬并且發生形變之后，就會脹開到軟土的位置上。

3 部件間用石灰砂漿進行接合。鋼筋在結構上水平放置。水平剖面（上圖）與1:20豎向剖面（下圖）/The elements are joined with trass-lime mortar. Rebar is laid into the structure horizontally. Horizontal section (above) and vertical section (below) at 1:20 scale.

部件之間的水平連接則是通過在水平的凹槽上放置兩個相連的鋼構件，再用石灰砂漿嵌入構件中完成的。這相當于在現場澆筑的夯土墻中使用的圈梁的效果。因為構件要伸入兩側的墻體的凹槽大約15cm，45cm寬的墻中構件外的部分就只有15cm，35cm寬的墻則只有5cm了。凹槽嵌入的深度大約為6cm。

如果夯土墻不是承重墻的話，它需要通過背面連接到建筑的結構體系中。可以通過在水平方向抹灰漿來連接墻體部件，再用一個包含鋼筋的Z字型托架來把墻裝配到建筑結構中去。因為土墻的變形較大，托架需要形成一種具有活動性的連接。因為使用了鐵質的墊片，結構體系和土墻立面都可以保持各自原來的保溫性。

最后，在完成了部件之間的定位和連接之后，還要小心地接合好接縫部分，讓墻面的紋理能保持整體上的節奏感。預制技術只有在完善了這一修飾工藝之后才能說真正地實現了技術突破，因為這意味著夯土墻視覺上的復古效果可以通過高效的建造方法來實現了（圖5-10）。

絕緣元素

4 相關工藝的最新發展：絕緣預制部件。這種工藝能造出兩面都有夯土圖案的土墻立面/The most recent step in development: insulated prefabricated elements. These make it possible to create an earth facade where the ramming pattern is visible on both sides.

到目前為止，還只有單層的墻能夠被預制。但為了生產中空墻而做的初步實驗已經在進行了，這種墻體會在兩片夯土墻之間夾一層輕質的絕緣層。這樣，墻的兩面就都能夠保持外觀的美感和土墻的物理特性了，還有一個另外的好處就是能在中空層里面裝配進制冷或制熱的管道。□collector: the earth walls function like hypocausts, capitalizing on their haptic properties while creating a comfortable indoor climate.

It took three months to finish the 160 pieces required for the Gugler project - these were then put in place over the course of a mere two weeks. The most recent projects completed with prefabricated elements are the Kr?uterzentrum in Laufen and the Swiss Ornithological Institute's visitor center in Sempach. due to improved workflow and increased production speed compared to the 1990s, the current ratio of production to installation in prefabricated parts is approximately 3:1.

The number of projects constructed with prefabricated materials has grown significantly: walls can be produced efficiently regardless of weather conditions and schedules are simpler to coordinate. In addition, transportation of commodities has become much easier - which also favours an indoor fabrication process. Even the demand for building with local materials can be fulfilled; for example, the elements of the Ricola Kr?uterzentrum were made of earth from an area in the vicinity of the building site. The distance from the production hall to the construction site was less than 3km. For large projects, it is often expedient to set up the production facilities locally, in order to utilize regional materials while decreasing transportation distances.

Mechanical Prefabrication

Since, as we mentioned above, this is largely a virgin territory, in order to develop prefabrication and further improve its efficiency, several new inventions have been required. Progress has primarily targeted at a reduction in the amount of physical labor required. The most strenuous task is filling the formwork with the material and compacting the mixture.

A machine was therefore developed to address this particular challenge by automatically distributing the earth within the formwork and mechanically compacting it with a moving rammer (fig.1). There is still a good deal of manual labor involved but a major part of it can be accomplished by this feeder mechanism. The machine also allows for the production of thinner walls, since the process no longer requires a person to be able to stand inside the form boards to ram the material. Long formworks enable the production of entire walls in a single segment with continuous horizontal layering. Afterwards, the elements can be cut to the appropriate size and installed in the same order on the building site.

5-7 生產及安裝過程示意/Schematic of production and installation process

8-10 生產及安裝過程示意/Schematic of production and installation process （5-10 圖片來源/Copyright: Ricola AG，攝影/Photos: Markus Bühler-Rasom）

Suspension and Transportation

Since the elements have very low tensile strength, forces must be evenly distributed along the lowest edge of the element during the installation process - blocks of unreinforced earth cannot be suspended from two points. With thinner and therefore lighter pieces, a wooden beam and several lifting straps suffice to distribute the weight. However, with larger and heavier elements, a specialized and custom-developed transport mechanism must be employed to allow adjustments on all three axes while setting the piece. To support the blocks from below, the first round of stamping includes a ladder-like structure made of round piping and iron rebar at the bottom. Anchor rods are then laid into these pipes and attached directly to the lifting gear with two steel plates (fig.2). The disadvantage of utilizing such an auxiliary construction is that it remains a part of the wall after placement. To reduce the complexity and avoid material waste, these steel constructions were replaced with wooden wedges, which could be stamped into the walls and driven through them after removing the formwork. As a result, the suspension straps can be attached directly through these gaps.

The straps attach the element to the lifting beam every 60 cm. The load is distributed through a system of cables between the block and the beams. The element is then aligned vertically onsite using two chain hoists (fig.3).

Installation Process

The element is placed on a bed of clay mortar approximately 1 cm thick, composed of the same materials. The friction-fit joining of the elements is actuated by their own weight, as the block embeds itself into the mortar. Clay must well out of the gap on all sides - this is the only way to ensure that the entire cavity has been filled. Once the block has been correctly placed on the mortar, its position is fixed with wooden wedges. After the mortar has dried, the entire load will bear down flat onto the element below. This is particularly important with rammed earth as compared with reinforced concrete, because

10 it cannot withstand tensile forces.

All the connections and joints between the individual elements are sealed during or just after the mounting process. However, preparation for this begins during production: a groove is notched into the vertical edges of the sides as well as the upwardfacing horizontal aspect. After the elements have been set, with a minimum gap of 1cm, the vertical grooves are filled with trass-lime mortar. Since these columns of trass-lime are stiffer than the earth and have different movement characteristics, the bottom of the groove is pitched with a trowel of soft clay. When the columns harden and then deform, they can expand into the softer clay.

The elements are horizontally connected by placing two contiguous iron rebar pieces in the horizontal grooves and embed them with trass-lime mortar. This functions similarly to the use of a ring beam for in situ rammed walls. Since there must be approximately 15cm covering the groove on both sides of the wall, it can be 15 cm wide in a 45cm thick wall, whereas a 35cm wall leaves only 5cm to play with. The groove is milled to a depth of about 6cm.

If the earth wall is not load bearing, it must be attached to the structural system on its inner fa?ade. Reinforcing the horizontal grouting in between the elements is well suited to this purpose. A Z-shaped bracket enclosing the rebar can be used to friction-fit the element to the building’s loadbearing structure. Due to the relatively strong creep deformation exhibited by earth, it should be executed as a movable connection. Due to the use of iron spacers, the structural system and the fa?ade retain their separate thermal envelopes.

Finally, after positioning and joining the elements, the seams are meticulously sealed and integrated into the rhythm of the striation. The breakthrough in prefabrication has only truly occurred since perfecting this retouching method, as this meant that the optical and archaic qualities of rammed earth could then be combined with an efficient fabrication process (fig.5-10).

Insulated Elements

So far, only single-leaf walls have been prefabricated. Preliminary tests for the production of cavity-wall modules have been conducted, in which a lightweight earth insulation layer is sandwiched between two rammed earth wythes. They can thus retain their aesthetic appearance and technical properties on both sides. As an additional benefit, the middle segment can be outfitted with heating and cooling conduits.□

編注/Editor's Note

i 德語Lehm Ton Erde (Loam Clay Earth) Baukunst GmbH譯為壤土-粘土-泥土建筑藝術股份有限公司

Prefabrication

Marko Sauer

Translated by SIMA Lei

作家、建筑評論家

2016-09-09