Abstract
The mechanical properties of high-toughness engineering cementitious composites (ECC) were tested, and a damage constitutive model of the materials was constructed. A new aseismic composite structure was then built on the basis of this model by combining aseismic joints, damping layers, traditional reinforced concrete linings, and ECC linings. A series of 3D dynamic-response numerical models considering the composite structure-surrounding rock-fault interaction were established to explore the seismic response characteristics and aseismic performance of the composite structures. The adaptability of the structures to the seismic intensity and direction was also discussed. Results showed that the ECC material displays excellent tensile and compressive toughness, with respective peak tensile and compressive strains of approximately 300- and 3-fold greater than those of ordinary concrete at the same strength grade. The seismic response law of the new composite lining structure was similar to that of the conventional composite structure. The lining in the fault zone and adjacent area showed obvious acceleration amplification responses, and the stress and displacement responses were fairly large. The lining in the fault zone was the weak part of the composite structures. Compared with the conventional aseismic composite structure, the new composite lining structure effectively reduced the acceleration amplification and displacement responses in the fault area. The damage degree of the new composite structure was notably reduced and the damage area was smaller compared with those of the conventional composite structure; these findings demonstrate that the former shows better aseismic effects than the latter. The intensity and direction of seismic waves influenced the damage of the composite structures to some extent, and the applicability of the new composite structure to lateral seismic waves is significantly better than that to axial waves. More importantly, under the action of different seismic intensities and directions, the damage degree and distribution area of the new composite structure were significantly smaller than those of the conventional composite lining structure.
Highlights
Earthquake damage investigations have found serious damage in tunnels running across a fault following a strong seismic event [1,2,3]. erefore, research on the seismic response and aseismic performance of tunnels across faults has attracted widespread attention
Liu et al [6] carried out a model test of the seismic response of a cross-fault tunnel, and results showed intense forces at the arch springing of the lining under the action of seismic waves. e authors recommended strengthening the aseismic fortification of the structure
Two structural types are considered: the new composite lining structure and a conventional composite lining structure. e new composite structure combines a damping layer, aseismic joints, reinforced concrete (RC) lining, and R/engineering cementitious composites (ECC) lining, and the R/ECC lining is arranged on the fault area (Figure 4). e conventional composite structure is composed of a damping layer, aseismic joints, and RC lining. e specific calculation plan is shown in Table 4. e three-dimensional seismic response calculation process of a cross-fault tunnel is divided into three steps
Summary
Earthquake damage investigations have found serious damage in tunnels running across a fault following a strong seismic event [1,2,3]. erefore, research on the seismic response and aseismic performance of tunnels across faults has attracted widespread attention. Li and He et al [4, 5] combined models and numerical analysis to study the seismic response properties and damage mechanism of tunnels crossing fault fracture zones; the authors revealed that the linings of fault fracture zones and adjacent areas are highly prone to damage. ECC have excellent tensile and compressive toughness and energy dissipation capacity, as well as strong adaptability to complex stress conditions under seismic events; these materials have been used in the aseismic field of high-rise building and bridge [13]. Numerical analysis is used to establish a 3D seismicresponse calculation model of the tunnel composite lining structure system-surrounding rock-fault interaction, and the seismic response properties, aseismic performance, and applicability of the composite structure are discussed. The average peak stress is 42.0 MPa, and the compressive strain corresponding to the peak stresses is 0.45%. e respective peak stress and strain of the ECC are approximately 1.4 and 3.0 times those of C30 concrete. us, the ECC has higher compressive strength and better compressive toughness than C30 concrete
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