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Concrete slabs resist lateral soil pressure that acts on foundation walls, which is critical to their stability. Backfilling soil against a foundation causes downward force of the soil, which becomes a lateral force pushing in on the walls. In short, slabs keep foundations walls in place. So, what if there is no slab? How is that pressure handled? That was the problem facing the team building这个项目在纽约北部。
这ICCF完美基础基础系统they used does not include a conventional slab;相反，使用了泡沫玻璃骨料。According to Project Manager Ben Bogie, roughly 250 lb. per sq. ft. of lateral force is pushing inward at the base of the foundation, where the greatest earth pressure occurs (it decreases closer to grade). That pressure needed to be addressed to ensure the foundation’s structural integrity. The engineer’s original solution was to pour concrete beams across the entire foundation, connecting the footings so they would push against each other. However, that idea ignored a primary objective of the project, which is to reduce concrete. “It would have required nearly the same amount of concrete as a slab for this house—without the slab,” Ben explains.
这answer came in the form ofStrataGrid geotextile fabric, which Ben describes as similar to chicken wire with its lattice web but made of 1/4-in.-diameter plastic;Tensar Geogrid产品would work for this application too. It gets fastened to the top of the foundation footing with a termination bar and a fastener schedule from the engineer—in this case, every 8 in. The downward force of the backfill soil clamps the termination bar and fabric in place. “The more downward pressure there is, the more lateral pressure there is, but also the more clamping pressure there is on the fabric, locking it in place,” Ben says, adding that this technique is commonly used in stacked-block retaining walls. Here, it accomplishes what a 4-in. concrete slab would from inside the foundation—without the embodied carbon load.
这product is 6-ft. wide and is cut to match the length of the footing section to which it is being fastened. It goes down folded to form two layers in an L shape; one leg comes out horizontally from the foundation wall and the other leg travels vertically up the wall. Then an 1/8-in. by 1-in. stainless steel termination bar is installed over the horizontal length; it is drilled and screwed onto the footing. The vertical leg is brought down to lay over the the horizontal lap, and the bar is sandwiched between the two layers to prevent the fabric from pulling out.
This is one of those cases when a common commercial detail makes its way into a residential application. Ben says this solution saved about $25,000 when compared to pouring a slab or the recommended concrete beams—plus it omitted roughly 60 tons of CO2 emissions.
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Kiley Jacquesis senior editor at Green Building Advisor.Illustration by Patrick Welsh.布莱恩·麦卡德（Brian McAward）的照片。
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15 Comments
This seems like an innovative product that could have a lot of uses.
I understand how geo-textiles would retain soil, but how that translates into stopping horizontal forces against the footing or foundation, or how it is deployed eludes me.
马尔科姆，
It's basically acting as a tension mat. The plastic mat has tensile strength so as long at it's attached to the foundation footing and wall, it holds it back in place. With all of the downward pressure on the horizontal portion of the mat, it creates enough friction that doesn't allow it to slide towards the inside of the building. Like I said, the way it's described in words is good but the diagram doesn't explain it very well and is kind of misleading. Unless I'm just not reading it right.
Nelson,
I've only used the geo-textile mats to to retain the substrate under roads on slopes, so this is all new to me. The problem is probably mine but what I don't get is:
- Is it the screwed connection that actually holds back the footings?
- 第二部分在哪里？它是否折叠在第一个形成三明治的折叠？如果是这样，两者之间有土壤吗？
- 如果它延伸到墙上，我根本看不到重点。当我对墙壁进行了设计以保留土壤时，它们的偏心尺寸很大。这些依赖于它们与上面的墙壁之间的好时机联系。L形垫子没有的东西。
What would be useful is a section that showed the geo-textile placement and some arrows representing the horizontal forces at play.
这让我想起了您提到的L形墙，但是如果连接被认为很重要，对，通常会阻止从力量推翻，正确吗？这只会防止横向移动向下。首先，这些螺钉确实看起来确实很奇特，但是我想有足够的螺丝。
and on second thought, 250 lbs. per sq. ft. isn't all that much really.
Tyler,
I would have been tempted to place it on the footings and pour the walls on top. But that's just back-seat driving. It works, and I think we now understand how.
Yeah that's an interesting thought. Some retaining wall builders will lay geogrid into the courses of their walls. similar concept.
马尔科姆,忍受我我不是一个工程师,但…screw connection is the point at which the forces are transferred from the termination bar, sandwiched between the two layers (there is only an upturned leg of material during the process of attaching the bar and fasteners) and in to the concrete footing. I can’t speak to the quantifiable forces at play here well, but I can say that the fastener selection, spacing, and minimum distance from edge, was calculated and specified by the engineering team.
This was very much an Ah Ha solution late one evening by the engineer and is inspired by the construction of stacked block retaining walls where a similar method is frequently deployed.
Ben,
感谢您的解释。我最初的错误是认为终止杆和螺钉就在那里将其固定在适当的位置，直到回填 - 有点像外部粉底隔热材料上的紧固件。一旦我将它们视为结构性连接，这一切都会有意义。
我参加聚会有点晚（我也不确定我也完全理解它），但这似乎是您的道路例子，除了他们在洞周围有一条高架的“道路”（即，房子。）。网格似乎可以稳定发掘周围的土壤。依恋的附件将所有东西锁定在一起。
Practical Engineering - How Soil Can Hold Up a Car
https://www.youtube.com/watch?v=0olpsn6_tcc
他介绍了细节和例子。对于道路，混凝土壁（主要）是为了装饰和保护土壤免受元素的保护。这似乎相似，但他们只是在这些目的中使用房屋。
我是一磅盐，当我是手臂椅时，仅根据本文进行思考过程（即没有进行计算）。
布伦丹，
Thanks. That makes sense. I think I underestimate the holding power of the screws and termination bar.
I would refer to this as geogrid, not so much geotextile, simply because of colloquial usage of what each respective product is used for and how they function.
您可能对此正确。与我们一起工作不是常见的材料类型，因此我可能会感到困惑。
我的评论被删除了吗？我发表了一个小图（Malcolm在他的2022年5月11日07:44 PM评论中回应的答复），但现在我看不到。
我只是想知道我的评论是否被故意删除，还是评论系统中的错误。
非常聪明！简单，有效，具有多个好处，包括降低成本。保持良好的工作。
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