DRIVEN PILES IN CENTRAL TEXAS
Pile driving in and around Austin and Central Texas is necessary for deep foundations because of the variety of soil conditions found between Marble Falls and Manor: alluvial (river) deposits, developmental fill sites, and severely expansive soil. In all of these natural and manmade formations, ground water can be found depending on the state of drought which typically weakens soils. The main advantage of driving piles or pilings versus other types of deep foundations is that each pile is driven to the resistance designated by an engineer, so that each pile is proven with each blow or drop from TX Pile’s 1000 to 5000 pound hammers. Also, pile driving is almost always more productive and uses less material than other forms of deep foundations leading to a cheaper, faster, and more quality controlled product.
Tens of thousands of piles have been driven along rivers from the Frio to the Brazos in the past 30 years by us. Majority of all of our work is along the Lower Colorado River and the Highland Lakes. The first of these lakes was Lake Austin which became the most silted in lake in the United States before Mansfield Dam was built. These silts now range from 60 feet deep to limestone at Mount Bonnell to exposed rock by the low water crossing below Mansfield Dam. The flow of the Lower Colorado River also determined the depth and the type of soils deposited. Stronger currents in the main channel were able to pick up and move rocks and gravel. While slower moving currents along the river banks would move sands and silts. During flood stages, clumps of driftwood and very fine-grained silts and clays would deposit up to 400 feet from the channel. All of this loose material never gets a chance to compact, so when structures are built along Lake Austin without a deep foundation, settling occurs and is exaggerated when the lake drops 12 feet every other year.
Along Lake Austin there are a few developments where the upper 10 to 20 feet of top soil were removed and filled with limestone rocks and boulders from utility cuts. There are also some man-made developments created from dredged material from the Lake Austin and random fill including curbs, water heaters, and refrigerators. These practices are not limited to around the lakes. On top of one of the highest hills in Lakeway, piles were driven 6 to 25 feet through fill. Designing a shallow or floating foundation in fill conditions is not advised because of the risk of the fill moving when a structure is built.
DRIVEN PILES IN EXPANSIVE CLAY
The Austin Area has some of the most failed and cracked slabs than anywhere in the United States because of expansive clays. The clay shrinks and swells depending on the moisture content from drought or flood conditions. This movement can be greater than 9 inches in some circumstances and extend over 15 feet below the surface. Piles are driven below this depth of active clay to overcome movement and support fully-suspended or voided slabs. To read more