Mitigation of reverse faulting deformation using a soil bentonite wall: Dimensional analysis, parametric study, design implications

Abstract

Recent major seismic events, such as the Chi-Chi (1999) and the Wenchuan (2008) earthquakes, have offered a variety of case histories on the performance of structures subjected to reverse faulting-induced deformation. A novel faulting mitigation method has recently been proposed, introducing a soft deformable wall barrier in order to divert the fault rupture away from the structure. This can be materialized by constructing a thick diaphragm-type soil bentonite wall (SBW) between the structure and the fault rupture path. The paper investigates the key parameters in designing such a SBW, aiming to mitigate the fault rupture hazard on shallow foundations. The paper employs a thoroughly validated finite element analysis methodology to explore the efficiency of a weak SBW barrier in protecting slab foundations from large tectonic deformation due to reverse faulting. A dimensional analysis is conducted in order to generalize the validity of the derived conclusions. The dimensionless formulation is then used to conduct a detailed parametric study, exploring the effect of SBW thickness w/H, depth HSBWl/H, and shear strength τsoil/τSBW, as well as the bedrock fault offset h/H, foundation surcharge load q/ρgB, and fault outcrop location s/B. It is shown that the wall thickness, depth, and shear strength should be designed on the basis of the magnitude of the bedrock fault offset, the location of the fault relative to the structure, and the shear strength of the soil. The efficiency of the weak barrier is improved using lower strength and stiffness material compared to the alluvium. A simplified preliminary design methodology is proposed, and presented in the form of a flowchart.

Investigating the Effect of Using Soil Bentonite Wall on Damage Mitigation of Steel Buried Pipelines Subjected to Reverse Fault Rupture

“…continuous steel gas pipelines," Soil Dynamics and Earthquake Engineering, Vol.86, pp. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] …”

“…the details of constitutive soil model are shown in [10]. Dense sand was used in this research which was calibrated and verified in previous research [9]. Table 1 Elastoplastic behavior for pipe was considered too.…”

“…Moreover, even the passage of buried pipeline parallel to fault line (figure 1a) which was recommended by joshi et al [7], can cause severe damages to buried pipelines in some critical conditions. In this research, by inspiring from researches of Fadaee et al [8], [9] with using a thick diaphragm-type soil bentonite wall (SBW) in a specific distance with buried pipelines which is parallel with fault line (figure 1a), SBW absorbs the deformation resulted from any possible reverse fault rupture and mitigates the damages caused to pipelines cross section (figure 2). More details about the performance of SBW in reverse fault rupture are shown in [8], [9].…”

Centrifugal and Numerical Investigation of Surface Fault Rupture Hazard Mitigation for Shallow Foundations Using Micro-Piles 

“…However, implementing a diaphragm wall might not be always regarded as the best solution due to the high relevancy of the diaphragm wall's efficiency with the exact place of faults. Adversely, a weak wall barrier consists of soil and bentonite was modeled by Fadaee et al (2016) to divert the fault rupture. Such Soil-Bentonite wall (SBW) demonstrates great capability due to its low strength and stiffness.…”

“…Strengthening foundation as the former strategy can be applied just by building the foundation in the form of a rigid body. Although strengthening foundations prevents structures from total collapse, the rotation of the structure is inescapable and correspondingly, the structure subjected to fault rupture would be nonfunctional (Fadaee et al, 2016). Therefore; the latter approach as a more rational strategy and capable of applying to both new and existing buildings contributes to many surveys that have been conducted to figure out how to deviate fault rupture and reduce the foundations' rotation.…”