A study of bearing capacity of the Jurassic moderately-weathered mudstone foundation

The Jurassic moderately-weathered mudstone in the Chengdu area is a typical red bed soft rock. Engineering practice shows that the standard recommended value of bearing capacity of the Jurassic moderately-weathered mudstone foundation in the Chengdu area is low, which leads to conservative foundation selection of high-rise and super high-rise buildings in this area, resulting in large project cost and long target construction period. However, there is no method to maximize the bearing capacity of the Jurassic moderately-weathered mudstone foundation. In this study, the foundation project of a super high-rise building in Chengdu is taken as an example, and 9 groups of deep well adit rock foundation load tests and 17 hole rock foundation side pressure tests are carried out, respectively, for the Jurassic moderately-weathered mudstone foundation to analyze the bearing capacity of the mudstone foundation and the appropriate value of bearing capacity characteristic. The correlation equation between the characteristic value of foundation bearing capacity and the characteristic parameters of rock mass obtained by ultrasonic logging test is established. The research results show that in the Jurassic moderately-weathered mudstone area, the characteristic value of the foundation bearing capacity obtained from the plate load test and the side pressure test of the rock foundation are similar and are 2−2.5 times larger than the maximum value recommended by the regional code DB51/T 5026—2001. The diameter of the bearing plate of the plate load test and the test depth of the side pressure test have no significant impact on the bearing capacity of the moderately-weathered mudstone foundation. Comprehensive analyses of parameters indicate that the characteristic value of the foundation bearing capacity has power and exponential increasing relationship with wave velocity of rock mass and integrity index of rock mass, respectively. The research results are of important reference value for the bearing capacity of the Jurassic moderately-weathered mudstone foundation.