Study On The Piles Characters Of Weathered Rock Foundition In Qingdao

Qingdao mantle of rock are buried shallowly,the burying depth varies immensely and the degree of rock mass weathering is extremely uneven in some places; the integrity is perfect, the stable degree is great, the compressibility is low, and supporting capacity is high. By collecting and analysing a large amount of data and relevant literature, the author gives a brief account of former investigations in this field, and conducts a preliminary study on the weathered rock foundation characteristics of the areas in Qingdao based on large-scale field tests. The major productions are as follows:1. Through experiments made about the static loading test of prestressed concrete pipe piles on the intense weathered rock, the author discovered several facts: the sedimentation of piles which is 6～7 meters long is only 6～7 mm when bearing 3000kN, the bearing capacity and deformation can meet engineering requirement. The supporting capacity of the precast pipe piles on the intense weathered rock is rather great,and the bearing capacity according to the static loading test is 1.6 times more than the designed bearing capacity ,and we should make full use of the bearing capacity in order to avoiding economic waste.2. Through experiments made about the static loading test of the artifical drilled short piles on the intense weathered rock, the author discovered several facts: The supporting capacity of the artifical drilled short piles on the intense weathered rock is rather great,while the sedimentation is relatively small. By the horizontal supporting capacity has been calculated, the author learnt that the shortest pile's horizontal supporting capacity can meet engineering requirement. As regard to the piles set into rock of L/D≤5～7 , tip resistance makes up 77.5～88.1% of the total bearing capacity, the shaft resistance may not be taken into consideration when designning, and can only be mentioned as a kind of safety margin.3.This paper based on software Ansys and the author analysised the influencing factors which influence the bearing capacity of the artifical drilled short piles on the intense weathered rock,such as rate of piles length and diameter,and the depth of rock-sockted. The following conclusion are drew: (1)there is dimensional effect to rock-socketed short piles and the sedimentation increases along with rate of piles length and diameter increases. (2) the question of socket length of short pile is discussed deeply. The calculation result make sure that short piles have deep effect also, 1～2 times of diameter is right. (3) The end capacity becomes higher and the shaft resistance becomes smaller when intensity of rock is higher, and when intensity of rock is low, the effect of sedimentation is obvious by improving bedrock condition.