Damage Identification And Alarming For Pile Plate Retaining Wall

Pile plate retaining wall is a common retaining wall structure, which is widely used in building engineering, transportation engineering, underground engineering et al. Retaining wall may be damaged under the effects of many factors in process of operation. So it is significant for disaster prevention and mitigation engineering in our country to identify and alarm damages within retaining wall timely and effectively. However, nowadays there is no a damage diagnosis method for retaining wall structures. Consequently, it is necessary to propose a damage identification method which is easy, nondestructive, sensitive, effective and feasible. And the damage indentification method is able to distinguish damage state of retaining wall, diagnose damage location of wall, identify damage degree and alarm safe stability of retaining wall so as to meet damage identification and alarming for retaining wall structures. In view of this, this paper is sponsored by project of “development of health diagnosis instrument for geotechnical retaining structures”(No.51027004) for national natural fund project and the project “Mountainous geotechnical engineering”(No.IRT1045) for changjiang scholars and innovative project team development plan of national ministry of education. And partial damage in pile plate retaining wall as well as retaining wall stability are identified and alarmed. Based on theory study, outdoor experiment, and numerical simulation, feasibility and effectiveness of the damage alarming method which is proposed in this paper is demonstrated. Main work includes:① Mechanical analysis of pile plate retaining wall-soil system is done, and a simplified mechanical model of retaining wall-soil system is established. Based on this, a finite element model of pile plate retaining wall-soil system is also established. This finite element model is modified through modal test and finite element modal analysis. And baseline finite element model of pile plate retaining wall is obtained.② It is analyzed sensitivity and robustness of wavelet packet frequency bands energy spectrum damage identification theory. On the basis of wavelet packet frequency bands energy spectrum, wavelet packet frequency bands energy ratio spectrum is introduced. And a new conception of residual frequency bands is proposed. Based on residual frequency bands, character frequency bands vector spectrum is created. Then damage eigenvector spectrum is established. Two damage identification indexes,energy ratio standard deviation(ISD) and energy ratio variation coefficient(IVC), are proposed. Then a damage identification method used for retaining wall is proposed based on these two damage indexes. Taking the baseline finite element model of pile plate retaining wall as an example, sensitivity, effectiveness and feasibleness of the damage identification method are demonstrated.③ Wavelet packet decomposition of impulse response function of stimulation and structural system responses is done. Based on impulse response function, an updated damage identification method is proposed. Sensitivity and feasibleness of this damage identification method is demonstrated through harmer vibration test. It is shown that this damage identification method doesn’t only distinguish damage state of pile plate retaining wall sensitively, but also diagnose partial location of retaining wall effectively and identify partial damage degree effectively.④ In order to eliminate dependence of wavelet packet frequency bands energy spectrum on stimulation, wavelet packet decomposition of virtual impulse response function of structural system responses is done. Based on vitual impulse response function, an updated damage identification method is proposed. Sensitivity and feasibleness of damage identification method based on virtual impulse response function is demonstrated through ambient stimulation vibration test. It is shown that this damage identification method can distinguish damage state of pile plate retaining wall sensitively, diagnose partial location of retaining wall effectively and identify partial damage degree effectively.⑤ Function relationship between earth pressure and coefficient of subgrade reaction is established. On the bisis of earth pressure, stablity state of retaining wall is diagnosed by damage identification indexes. Retaining wall is in critical stability state, when alarming index is limit value. So damage index can be used to alarm stability state of retaining wall.All of studies show that the damage identification method proposed in this paper doesn’t only distinguish damage state of pile plate retaining wall sensitively, but also diagnose partial location of retaining wall effectively and identify partial damage degree effectively. In addition, stability of retaining wall can be alarmed througu damage index. So damage identification method proposed in this paper can be used for health diagnosis of retaining wall. These conclusions have academic significance and application value to civil engineering disaster prevention.