The reflection observed with TDR cable tester depends on various factors, including type of cable fault. The most important benefit of TDR is that the location of the fault and the type of it can be diagnosed using the transmission time and reflection properties, respectively.One of the most important parameter of cable is impedance (Zo) that is defined as a function of inductance and capacitance:Basically, the faults led to a change in the transmission line properties (L, R, and C), and in impedance that are detectable by TDR system. According to the linear transport theory, we can know that:Z1 = characteristic impedance on the deformed section of cable. Z0 = the characteristic impedance of the non-deformed cable.The reflection of TDR pulse is shown for different impedance mismatches in Fig. 2. For coaxial cable, the characteristic impedance depends on the cable geometry.where a and b are the radius of inner and outer conductor. μ and ∈ are magnetic permeability and dielectric permittivity, respectively.Changes in ρ caused by shear appear as sharp downward spikes in Fig. 8. Installing the TDR cable and inclinometer in the slopes overlooking the Darian Dam bottom outlet.the TDR waveform, and the amplitude of the spike increases in direct proportion to the magnitude of shear deformation. The changes in ρ caused by the tensile deformation can be seen as a subtle, trough-like depression in the cable signature and their diagnosis is much more difficult, than the signal resulting from the shear. (O'Connor and Dowding, 1999).Laboratory tests by Su (1987) show that the cables respond differently to extension and shear. So grouted cables into pipes, which were later cut, and either pulled (extended) or sheared until first the uncut grout and then the cable failed. Reflection signatures in Fig. 3 produced at increasingly larger extension (3a) and shear (3b) displacements show that extension failure produces a broader, smaller amplitude reflection. Shearing produces a narrower, larger amplitude reflection. The insets show the differences in the geometry at the failed ends of the cable. Extension does not produce as severe a change in the distance between the inner and outer conductor of the coaxial cable. This observation is consistent with the smaller reflected signal associated with extension failure.