# Experimental Research on the Properties of Rock-Filled Concrete
## 3 Experimental Tests for the Properties of Rock-Filled Concrete
### Ultrasonic Test  
In ultrasonic tests, a nonmetal ultrasonic instrument (model: RS-ST02), made by the Wuhan Yanhai Company (Wuhan, China), was used. Ultrasonic tests, which can indirectly indicate the quality of RFC by the velocity of ultrasonic transmission in RFC, is processed by a single emission and double receiving sonic logging method. The flow the of sonic logging method is as follows [27]: (1) Fill the borehole with water; (2) check whether the instrument and transducer work properly; (3) put a single transducer down at the bottom of the borehole using a cable; (4) properly connect the transducer with one emission head and two receiving heads to the emission port and receiving port of the instrument; (5) take data at intervals of 0.50 m from bottom to top, and record the time interval between receiving heads; (6) get the velocity of the longitudinal waves. The whole ultrasonic test process should be in accordance with the \"Technical specification for inspection of concrete defects by ultrasonic method (CECS21:2000)\" (China Association of Engineering Construction Standardization, 2001) [28]. The change trend of ultrasonic wave velocity with depth in each borehole is shown in Figure 8.  
Figure 7: Relationship between permeability of RFC and depth by histogram. As seen in Figure 8, the average ultrasonic velocity in borehole No. 1, is about 2814 m/s, mostly distributed in the 2250 m/s\(\sim\)3500 m/s range. At the depth of 10.0-10.5 m., the ultrasonic wave velocity was greatly reduced, which shows that there exist large defects, voids or relatively loose concrete; in other places, the ultrasonic wave velocity changed little, showing that RFC is relatively homogeneous, and the quality of RFC at the base is slightly better than at the top, which is in accord with the pressure water test results in this borehole. The pressure water test shows that the permeability in this borehole area gradually reduces as depth increases, which suggests that the fractures at the top of the dam are more than at the bottom, but it does not agree with the results of the core porosity test, which shows that the porosity at the top is less than at the bottom. A possible reason is that the interconnection of voids and fractures at the top area of dam is relatively better than in the bottom area, which can result in relatively high permeability at the top of dam although with low porosity of RFC in this area. Nevertheless, the core porosity test only based on specimens cannot entirely indicate the distribution of voids and fractures within RFC. The ultrasonic velocity in the No. 3 borehole is generally above 2000 m/s, with an average of 2948 m/s. At the depth of 0\(\sim\)2.0 m, the ultrasonic velocity is relatively low, about 2000 m/s, but at the depth of 2.0-2.5 m, the ultrasonic velocity is significantly higher than elsewhere, which could be due to embedded dense rock blocks, leading to a high ultrasonic velocity at this area. At a depth below 9 m, the fluctuation of ultrasonic velocity is significant. The pressure water test in borehole No. 3 shows that at the depth of 6.4-10.7 m, the dam permeability is far higher than in other parts, but on the contrary, there is no obvious reflection on the ultrasonic velocity, which may be due to vertical fractures in this part, whose orientation may be coincident with the transmission direction of ultrasonic waves, not resulting in obvious changes on ultrasonic velocity yet having great impact on permeability. The ultrasonic velocity in borehole No. 4 is generally above 2200 m/s, with an average of 3061 m/s. At the depth of 8.5-9.5 m, the ultrasonic velocity is higher, which means that there might be dense rock  
Figure 8: Relationship between ultrasonic velocity of RFC and depth. blocks, causing high ultrasonic velocity through the rock blocks. The water pressure test in borehole No.