Foundation Tech, Inc., a California consulting and repair contractor specializing in soil stabilization and foundation repair solutions and services was selected by the largest China based airport repair and maintenance contractor to assist in repair of the Beijing Capital- PEK Airport runways.

Severe drought conditions over the past eight years in Beijing have caused a large fissure in the subsoil directly underneath the Beijing Capital Airport, extending over 2.3 kilometers. The fracture crosses directly underneath two of Beijing’s three main runways, causing severe settlement of the 60-90 cm deep concrete runway and taxiway slabs. Settlement of 7cm to 25cm for the five meter square two layered slabs has occurred along the complete length of the 2.3 kilometer crack. This has caused hazardous conditions for not only airport vehicle traffic but also for aircraft landing and taxiing along the affected areas.

Multiple attempts to repair the settled slabs on both the runways as well as taxiways has offered poor results due to the continued widening of the crack and the subsequent soil erosion and slab settlement along the entire runway. Grinding and pouring an overlayment including pumping concrete into the crack[s], to level the hundreds of five square meter slabs was not a viable option due to the time frame to cure, as well as logistical issues with installation crews and construction equipment being on an active runway.

Jerry Bronstrup of Foundation Technology suggested utilizing HMI polyurethane foam for a quick and lightweight alternative over conventional replacement methods to both level the affected slabs and fill the voids which was very effective. Ground penetrating radar was used to determine the total breadth and width of the fissure. It was then decided to utilize HMI’s RR401 heavy lift geotechnical foam due to its fast tact free time and high compressive strength skin that avoids concrete adhesion. The Wisconsin Manufacturer’s 4lb. per cubic foot foam was perfect for the job and would stand up to the airport runways and taxiways heavy loads. Subsequent onsite tests were performed to prove the feasibility of the RR401 polyurethane foam as a viable alternative for slab lifting and void fill. Over 120,000 lbs. of foam was required to complete the project.