Abstract: The conventional method of determining rock mechanical parameters now can only obtain the overall strength of the rock; while in the weathered layer of ancient buildings rock constructional elements, of which the mechanical parameters gradually change. It is not enough to study the stability and durability of rock ancient buildings. So a method with integrated use of on-site sonic CT test, surface rebound and laboratory test to obtain the mechanical parameters of rock constructional elements is proposed. The method is put into action as follows. The longitudinal wave velocity distributions along the depth profile in the rock constructional elements are acquired by the on-site sonic CT test. The statistical relation of the mechanical parameters and wave velocity is obtained by selecting rock on-site that analogous to the rock constructional element studied to do the indoor mechanical tests and the wave velocity test. The mechanical parameters distribution along the depth profile in the rock constructional elements is derived by combining the outcomes mentioned above; based on this, the relationship between mechanical parameters and depth within the weathered layer is analyzed. The relationship between the surface compressive strength ratio and the weathered depth is derived by weathered depth studying and surface rebound test on the typical rock constructional element in different weathering zones. This method is systematically introduced in this paper with the example of Guyue Bridge in Yiwu built in the Song Dynasty. This paper studied the relationship between mechanical parameters and depth within the weathered layer and the relationship between surface strength of rock constructional element and weathered depth of weathered rock constructional element which were in the bearing structure of the Song Dynasty Guyue Bridge in Yiwu. The studies show that: in the bearing block stone of the Song Dynasty Guyue Bridge, the compressive strength ratio and the elastic modulus ratio vary negative-exponentially with the depth in weathered layer; the relationship between compressive strength ratio of surface and weathered depth conforms to the two order polynomial.

Key words: weathering, rock constructional element, mechanical parameters, sonic test, rebound test