Study On Anchorage Properties Of Slope Rockmass And Its Engineering Applications

Rockmass anchorage is the very important branch of the geotechnical engineering field. Meanwhile, research on anchorage properties of rockmass is one of the rockmass anchorage cores. Anchorage technique is the most prevalent, the most economical and the most effective measure of reinforcement and protection of rock slope mass. Therefore, the relatively profound and systematic studies on anchorage properties of slope rockmass and its engineering applications are carried out concerned with the mechanical properties, long-term performance, durability, and other problems.The main contents are as follows:(1) Model research on distribution regularity of shear stress on anchorage end of prestressed cable is carried out according to half space with concentrated force in normal direction on boundary based on the elastic theory. By the analysis of the distribution characteristics of shear stress in practical engineering and field experiment, the performance of shear stress on anchorage end can be modeled with the introduction to comprehensive parameter ? which is correlated to prestress, length of anchorage end, rock strength, and grout body strength and comprehensive parameterβwhich is correlated to the peak position of shear stress and the diameter of anchorage end. Ultimate load capacity can be calculated according to the compression strengthσ_c and internal friction angleφof the interface of rockmass and grout body and the approximately linear inverse proportion relation. Meanwhile, the design length of anchorage L_d multiplied by 2tanφmakes the practical length of anchorage end L_s which is calculated by the paper's method. Finally, two cases calculation and analysis show that the research production is reasonable.(2) Bolts with single borehole and wholly grouted multiple bars can be used to solve the reinforcement of shallow and superficial rock mass of unfavorable geologic conditions and worse rock characters. The test on bolts is carried out based on the practice of the tailwater slope which is the bank of the Goupitan hydropower station in Wujiang river. The research shows that the basic properties of bolt is good. The time-dependent axial force of bolt is analyzed based on monitoring data, and combining with the research results of predecessors the concept of the bolt size effect is put forward. The practical project shows that bolts are reasonably designed, conveniently constructed and very economical, which is worthy to be popularized in other similar projects.(3) Based on improved Nishihara model which is composed of a new nonlinear viscoplastic body (NVPB), the calculation formula of long-term prestress variation is deduced after the coupling model is established, which is concerned with the coupling effects of the load of prestressed cable and the creep curve of rock slope masses. The calculation formula can indicate the actual regularity of prestress loss variation under the various conditions. The comparison between the on-site monitoring data of prestressed cable located in the tailwater slope which is the bank of the Goupitan hydropower station in Wujiang river and theoretical calculations result shows that the calculation formula is available and reasonable. The research results can give some suggestions or criteria for the long-term performance of the prestressed anchorage. Meanwhile, the engineering measures of the improving long-term performance of the prestressed anchorage are put forward.(4) A calculation formula of limit to growth when grout body cracked is deduced from the hoop stress of prestressed cable grout body, which is concurred between the hoop tension stress is created by pretension and the uniformly corrosion expansion force by cable body. A estimation expression of the service life when grout body of prestressed cable cracked in high and steep slope rockmass is solved based on predecessors' research production, which is the base of the research on the durability of prestressed anchorage. At last, four factors related to service life and their relative importance are discussed, which are combined with the reinforcement engineering's 2000kN and 3000kN prestressed cable located in the excavation slope rockmass upward an altitude of 1885 meter of the left bank at Jinping first stage hydropower station in Yalongjiang river. It is concluded that: the pretension is the most insensitive factor. With the increase of the pretension, the service life decreases, in which the curve is linear. The choice of the prestress value chiefly depends on the guarantee of engineering stability. The influence of the cable body diameter is relatively much stronger than the pretension. With the increase of the cable body diameter, the service life increases, in which the curve's gradient is slightly steepening. The strand should be possibly separately laid out. The influence of bond thickness is a little stronger than the cable body diameter. With the increase of bond thickness, the service life also increases, in which the curve's gradient is slightly steepening. The diameter of the bore hole should be reasonably optimum. Whereas, the compression strength of grout body is the most sensitive factor that affected the service life. With the increase of the compression strength, the service life increases, in which the curve's gradient is also slightly steepening. Meanwhile, the engineering measures of the improving durability of the prestressed anchorage are put forward.(5) The results and conclusions of the study on anchorage properties of slope rockmass are utilized in the No.158 fault at Maya high and steep slope located in the Shuibuya hydropower station in Qingjiang river. Combination the feedback analysis of the in-site monitoring data included the tiltmeter, the multi-point extensometer, the anchor dynameter, and crack's opening of the joint meter with the FEM calculation results of the axial force along distance of anchorage hole, and the rockmass displacement, the anchorage properties in rock mass fault of slope are analyzed and the concept of connecting anchorage in rock mass fault of slope is proposed. The research results can be used for reference to the similar engineering.