預(yù)制工藝

馬爾科·索爾

司馬蕾 譯

預(yù)制工藝

馬爾科·索爾

司馬蕾 譯

節(jié)選自馬丁·勞奇的《優(yōu)雅的泥土——夯土建筑與設(shè)計(jì)》， 奧托·卡普芬格和馬爾科·索爾（編著），細(xì)部出版社，慕尼黑，2015年， 第118-121頁(yè)。由細(xì)部出版社再版。

預(yù)制工藝為夯土建筑提供了一種新范式，這種技術(shù)無(wú)論從定性還是定量的角度來(lái)說(shuō)都是一次巨大的飛躍。它讓夯土建筑的建造達(dá)到了一個(gè)新水平，也讓更多的項(xiàng)目可以考慮使用夯土。這種分離建筑的生產(chǎn)和安裝過(guò)程的做法更為經(jīng)濟(jì)，因?yàn)樵谑┕がF(xiàn)場(chǎng)的作業(yè)中，相比雇傭一群工人在現(xiàn)場(chǎng)夯土、慢慢地壘起建筑的做法，起重機(jī)能夠在工期很緊的情況下很快地把成品部件搭建好。因?yàn)椴考谠旌脮r(shí)已經(jīng)是干的了，整合分包出去的各項(xiàng)工種時(shí)可以做到無(wú)縫銜接，這也大大地縮短了建造所需的時(shí)間。雖然生產(chǎn)這些墻仍然是一項(xiàng)時(shí)間密集型的工作，但生產(chǎn)和安裝的時(shí)間變得更容易規(guī)劃和協(xié)調(diào)了。

因?yàn)檫^(guò)去幾乎沒(méi)有離開(kāi)現(xiàn)場(chǎng)在別處進(jìn)行夯土的先例，夯土建筑中的預(yù)制工藝幾乎是個(gè)未知的領(lǐng)域，但現(xiàn)在已經(jīng)開(kāi)始出現(xiàn)了這方面的嘗試。相關(guān)的技術(shù)和結(jié)構(gòu)要求變得更為細(xì)致，并開(kāi)始通過(guò)優(yōu)化設(shè)計(jì)來(lái)探索解決方案。在這座最初的預(yù)制夯土建筑的大體部分基本完工之后，后續(xù)的修整的工作也進(jìn)化了很多，這讓由各種部件組成的墻體看上去就和在現(xiàn)場(chǎng)建造的夯土墻一模一樣。

但施工過(guò)程的規(guī)劃仍需要繼續(xù)進(jìn)行改進(jìn)，例如在工程的初期階段，盡管很難，仍要快速明確對(duì)這些夯土部件的要求。這涉及到施工的管理和生產(chǎn)間的密切配合，而其中對(duì)預(yù)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(diào)整部件的尺度以適應(yīng)不同的空間高度。而部件的長(zhǎng)度還要考慮到把部件搬送就位的起重機(jī)的荷載限制，這一長(zhǎng)度是由起重機(jī)允許的最大重量、墻的高度和寬度共同決定的。這種在規(guī)劃和生產(chǎn)的交接中會(huì)出現(xiàn)的交互問(wèn)題都需要仔細(xì)地進(jìn)行評(píng)估。

為了盡量控制部件的數(shù)量以實(shí)現(xiàn)較低的造價(jià)和較短的工期，甚至連起重機(jī)的擺放位置、根據(jù)機(jī)械臂外展距離確定的最大負(fù)荷都需要進(jìn)行考慮：靠起重機(jī)近的部件可以相對(duì)重些，也可以設(shè)計(jì)的長(zhǎng)一些。位于森帕赫的瑞士鳥(niǎo)類研究所的項(xiàng)目就仔細(xì)地評(píng)估了這些方面的要素。

但同時(shí)，這也讓建造的技術(shù)也變得簡(jiǎn)單多了：預(yù)制部件的細(xì)部都是標(biāo)準(zhǔn)化的，即使非熟練工人也可以來(lái)施工。建造工作也可以分配給多個(gè)實(shí)施方來(lái)分擔(dān)，這對(duì)夯土建筑行業(yè)整體也是有益的。

生產(chǎn)優(yōu)勢(shì)

世界上第一個(gè)預(yù)制夯土部件是在1997年由Lehm Ton Erde Baukunst GmbHi設(shè)計(jì)的一面起居室里的墻。這面墻被安裝在木結(jié)構(gòu)的建筑中，乍看之下在施工上幾乎不可能實(shí)現(xiàn)： 屋架的建造工期有限，進(jìn)度很緊，此外，工程計(jì)劃在一月份進(jìn)行，這個(gè)時(shí)期因?yàn)樗獌龅年P(guān)系不可能在場(chǎng)地上進(jìn)行夯土。因此才出現(xiàn)了想通過(guò)起重機(jī)在建造木構(gòu)架的同時(shí)把夯土墻吊裝進(jìn)去的解決方案，也催化了土質(zhì)建材的預(yù)制化進(jìn)程。

這一時(shí)期的第一個(gè)大規(guī)模項(xiàng)目是古格勒打印機(jī)公司位于奧地利皮拉赫的一個(gè)辦公樓項(xiàng)目。項(xiàng)目中構(gòu)成建筑內(nèi)墻的標(biāo)準(zhǔn)化的部件被互相堆疊在一起，再把節(jié)點(diǎn)連接起來(lái)。這一墻體部件里包含了用地源熱泵供能的通風(fēng)管道，夯土墻的功能則類似于地暖，利用其觸感特點(diǎn)，創(chuàng)造出舒適的室內(nèi)環(huán)境。

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

1 機(jī)械預(yù)制能減少勞動(dòng)力的需求，并加快了生產(chǎn)過(guò)程。這臺(tái)機(jī)器由Lehm Ton Erde Baukunst GmbHi研發(fā)/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(kāi)發(fā)懸掛系統(tǒng)來(lái)進(jìn)行裝吊。這種系統(tǒng)也能讓部件實(shí)現(xiàn)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(yù)制材料來(lái)進(jìn)行建造的項(xiàng)目數(shù)量也有了顯著的增長(zhǎng)：預(yù)制墻體可以快速地進(jìn)行生產(chǎn)而不用考慮天氣情況，這讓工程進(jìn)度的調(diào)整變得容易多了。此外，現(xiàn)在的成品運(yùn)輸也變得更容易了，這也有利于推廣室內(nèi)預(yù)制工藝。即使是采用本地材料來(lái)進(jìn)行建造的需求也可以被滿足，例如位于勞芬的草藥中心項(xiàng)目使用的土就是基地本身的土方，生產(chǎn)預(yù)制品的工廠距離工地還不到3km。對(duì)這種大型項(xiàng)目來(lái)說(shuō)，在當(dāng)?shù)刂苯釉O(shè)工廠往往更為經(jīng)濟(jì)，既可以利用當(dāng)?shù)氐牟牧?，也能減少運(yùn)輸?shù)木嚯x。

機(jī)械預(yù)制

正如上文所說(shuō)，夯土建筑的預(yù)制領(lǐng)域基本是片處女地，為了發(fā)展預(yù)制的工藝、進(jìn)一步提高其生產(chǎn)效率，也應(yīng)需求出現(xiàn)了一些新的發(fā)明。在工藝上的改進(jìn)主要體現(xiàn)在減少生產(chǎn)部件所需的人力。而人力勞動(dòng)中最艱苦的部分就是用原材料填滿模具并把填料壓實(shí)。

為此，馬丁發(fā)明了一臺(tái)機(jī)器，專門(mén)用來(lái)把土自動(dòng)分配到模具里，再用一個(gè)運(yùn)動(dòng)的錘子來(lái)夯實(shí)它（圖1）。這一工作還是需要不少人力來(lái)參與，但這個(gè)送料機(jī)已經(jīng)能完成其中的大部分工作了。因?yàn)橐呀?jīng)不需要讓一個(gè)人來(lái)站在模具里面夯土，這種機(jī)器也能用來(lái)直接生產(chǎn)比較薄的墻體。此外，也能使用比較長(zhǎng)的模具，通過(guò)一片片地連續(xù)堆疊水平土層來(lái)生產(chǎn)整面墻體，之后根據(jù)需要的尺寸把墻體切割開(kāi)，再在現(xiàn)場(chǎng)按同一順序安裝起來(lái)。

懸掛和運(yùn)輸

因?yàn)楹煌敛考目估芰苋?，就像沒(méi)法從兩頭提起沒(méi)有加固過(guò)的土一樣，在安裝過(guò)程中，底面上的受力必須要非常均勻。對(duì)于較為輕薄的部件，通過(guò)加設(shè)木梁和幾條捆帶能幫助分散重量。但是對(duì)更大和更重的部件來(lái)說(shuō)，就需要訂制開(kāi)發(fā)專業(yè)的機(jī)械運(yùn)輸系統(tǒng)，以便在放置它時(shí)實(shí)現(xiàn)3個(gè)維度上的同時(shí)調(diào)整。為了從下方托住部件，沖壓制造墻體的第一層時(shí)在墻底加裝了由圓形的管道和鋼筋構(gòu)成的階梯狀構(gòu)件。安裝時(shí)在管道下面鋪設(shè)錨桿，再用兩個(gè)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(diǎn)是在部件安裝完后，金屬件會(huì)露出來(lái)一部分。為了減少工藝的復(fù)雜性，也減少材料的浪費(fèi)，這種鋼質(zhì)構(gòu)件現(xiàn)在已經(jīng)用木楔來(lái)代替了。木楔在制造墻體時(shí)先嵌入其中，脫模時(shí)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(guò)每隔60cm的捆帶固定到梁上，體塊和梁間的繩索系統(tǒng)能幫助荷載分布均勻，之后再通過(guò)兩個(gè)吊鏈讓墻體豎立起來(lái)（圖3）。

安裝過(guò)程

墻體部件被放在由純粘土砂漿構(gòu)成的約1cm厚的墊層上。部件之間利用自身重量通過(guò)摩擦粘合，上部的部件會(huì)嵌入到砂漿中去。連接面四周的粘土砂漿必須涌出來(lái)，這樣才能保證砂漿包裹住了整個(gè)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(gè)部件的重量會(huì)傳導(dǎo)到下部的部件上。因?yàn)楹煌敛荒艹惺芾?，這一步驟對(duì)于夯土部件來(lái)說(shuō)比對(duì)鋼筋混凝土部件重要得多。

各個(gè)部件之間的連接件和節(jié)點(diǎn)都會(huì)在裝配時(shí)或者完工之后再次封實(shí)。然而準(zhǔn)備的工作在生產(chǎn)部件的時(shí)候就開(kāi)始了：各個(gè)面的垂直角和水平的向上面上都已經(jīng)切開(kāi)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?yàn)槭冶韧劣玻⑶液屯恋男巫兲匦圆煌?，要先在槽的底部墊一層軟粘土。當(dāng)石灰塊變硬并且發(fā)生形變之后，就會(huì)脹開(kāi)到軟土的位置上。

3 部件間用石灰砂漿進(jìn)行接合。鋼筋在結(jié)構(gòu)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(guò)在水平的凹槽上放置兩個(gè)相連的鋼構(gòu)件，再用石灰砂漿嵌入構(gòu)件中完成的。這相當(dāng)于在現(xiàn)場(chǎng)澆筑的夯土墻中使用的圈梁的效果。因?yàn)闃?gòu)件要伸入兩側(cè)的墻體的凹槽大約15cm，45cm寬的墻中構(gòu)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(guò)背面連接到建筑的結(jié)構(gòu)體系中?？梢酝ㄟ^(guò)在水平方向抹灰漿來(lái)連接墻體部件，再用一個(gè)包含鋼筋的Z字型托架來(lái)把墻裝配到建筑結(jié)構(gòu)中去。因?yàn)橥翂Φ淖冃屋^大，托架需要形成一種具有活動(dòng)性的連接。因?yàn)槭褂昧髓F質(zhì)的墊片，結(jié)構(gòu)體系和土墻立面都可以保持各自原來(lái)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(jié)奏感。預(yù)制技術(shù)只有在完善了這一修飾工藝之后才能說(shuō)真正地實(shí)現(xiàn)了技術(shù)突破，因?yàn)檫@意味著夯土墻視覺(jué)上的復(fù)古效果可以通過(guò)高效的建造方法來(lái)實(shí)現(xiàn)了（圖5-10）。

絕緣元素

4 相關(guān)工藝的最新發(fā)展：絕緣預(yù)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(yù)制。但為了生產(chǎn)中空墻而做的初步實(shí)驗(yàn)已經(jīng)在進(jìn)行了，這種墻體會(huì)在兩片夯土墻之間夾一層輕質(zhì)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(gè)另外的好處就是能在中空層里面裝配進(jìn)制冷或制熱的管道?！鮟ollector: 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(chǎn)及安裝過(guò)程示意/Schematic of production and installation process

8-10 生產(chǎn)及安裝過(guò)程示意/Schematic of production and installation process （5-10 圖片來(lái)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(yǔ)Lehm Ton Erde (Loam Clay Earth) Baukunst GmbH譯為壤土-粘土-泥土建筑藝術(shù)股份有限公司

Prefabrication

Marko Sauer

Translated by SIMA Lei

作家、建筑評(píng)論家

2016-09-09