2 Volumes Final Proceedings - Washington 1984.pdf - IARC Research

19I/Bearing platformFIGURE 2Inserted pile foundation.FIGURE 3Poured pile foundation.around the pile. The burial depth was 8-10 m.During this period, these piles were used in abaut50 large and middle-sized bridges. No obvious deformationhas been found since they were completed,and they are still in regular operation.The successful use of bored piles in highwaybridge engineering was folluwed by their trial applicationto house building in the early 1970s.The loading characteristics of various kinds ofbored piles were studied to acquire data for designingfoundations with them. 'pwo sectors in theQinghai-Xizang Plateau with differing featureswere chosen as the test sites. Vertical and horizontalloading tests of inserted, driven, andpoured piles were made (NICARS, 1977). Based onthe results, a test house with an inserted-pilefoundation and an engineering production buildingwith a driven-pile foundation were constructed onthe Plateau (FSDI, 1978). The former was theboiler room and kitchen of the Frost Research Stationand the latter was the water tauer, boilerroom and puap house, and electrical machinery roomof a pump station. Hollow reinforced concretepiles were used at both sites; they had a diameterof 40 cm, were buried to a depth of 6 m, and ventilationwas applied to keep the ground frozen.The lmilding was completed in 1977 and no obviousdeforrmtion has yet been discovered.Meanwhile, two test houses with poured-pilefoundations -- the residences of the Frost ResearchStation -- were designed by the JingtaoFrost Station, located in the pernufrost region ofthe Great Xing'an Mountains (He and Xiao, 1981).A raised foundation was not used in this case, usingthe thawing disc of ground to keep the basetemperature inside the hildings as constant aspossible. Because of the required maximum computedthawing depth of the disc and the Boil bearingcapacity, the designed pile diameter and burialdepth were 26 cm and 7.5 m respectively. 'She twobuildings were completed in 1976, and observationsand tests verify that the strength of the concreteand the bearing capacity of the piles all met thedesign specifications.IBearing platformFIGURE 4 Buried pile foundation.While bored-pile foundations were tested andput into use, experiments on other types of deepfoundations were atarted in various petmeErostareas. For instance, buried-pile foundations weretested in house construction in the permfrost regionof the Great Xing'an Mountains (Qiqiha'rRailway Mmin., 1975; Wang, 1982). The pile foundationwas composed of prefabricated, reinforcedconcrete pillars (or rock pillars with mortar),ring-shaped base (or widened base), and bearingplatform (Figure 4). The construction was carriedart in sequence as follms:1) Excavate the foundation pit.2) kry the base.3) Put the piles vertically on the base.4) Refill the pit.5) Pour in concrete to cast the bearing platform.The tests were conducted at two separatesites; at one a raised foundation was constructedto provide natural ventilation to prevent theground from thawing. The section of pile was 20 x