Journal of Geotechnical and Geoenvironmental Engineering

Tunnels are constructed increasingly close to existing buried structures, including pile foundations. This poses serious concerns, especially for tunnels built beneath piles. Current understanding of the global tunnel–soil–pile–building interaction effects is lacking, which leads to designs that may be overly conservative or the adoption of expensive measures to protect buildings. This paper presents outcomes from 24 geotechnical centrifuge tests that aim to investigate the salient mechanisms that govern piled building response to tunneling. Centrifuge test data include greenfield tunneling, pile loading, and tunneling beneath single piles and piled frames, all within sand. The global tunnel-piled frame interaction scenario is investigated using a newly developed real-time hybrid testing technique, wherein a numerical model is used to simulate a building frame, a physical (centrifuge) model is used to replicate the tunnel-soil-foundation system and structural loads, and coupling of data between the numerical and physical models is achieved using a real-time load-control interface. The technique enables, for the first time, the modeling of a realistic redistribution of pile loads (based on the superstructure characteristics) in the centrifuge. The unique dataset is used to quantify the effects of several factors that have not previously been well defined, including pile installation method, initial pile safety factor, and superstructure characteristics. In particular, the results illustrate that pile settlement and failure mechanisms are highly dependent on the pretunneling loads and the load redistribution that occurs between piles during tunnel volume loss, which are related to structure weight and stiffness. The paper also provides insight as to how pile capacity should be dealt with in a tunnel-pile interaction context.

The behavior of interfaces between granular materials in zoned embankment dams can influence their overall behavior. Soil–structure interfaces have been largely studied, but only a few analyses of interfaces between the granular materials composing rockfill dams have been realized. Consequently, there is a need to consider the influence of material interfaces within dams. Numerical modeling of a rockfill dam was performed to simulate its mechanical behavior during the construction phase. The behavior was analyzed based on the numerical methods used to model the interfaces and on interface characteristics through sensitivity analyses. Particular attention was paid to the influence of interface shear strength on the dam shear deformations, settlements, and plasticity. The numerical results highlight that the contact condition and the interface characteristics influence the dam behavior. Low shear resistance of interface engenders an increase of relative displacements, settlements, and shear strains in the dam. Moreover, the dilative behavior of the interfaces also affects the overall dam behavior.

The effects of shaking history on cone penetration test (CPT)–based liquefaction triggering correlations for clean saturated sand are examined by using cone penetration resistance and cyclic strength data pairs from dynamic centrifuge model tests. Three model tests on a 9-m-radius centrifuge examined the liquefaction responses of level profiles of saturated Ottawa F-65 sand subjected to multiple (17–29) shaking events that produced successive changes in density and model response characteristics. Inverse analysis of data from dense accelerometer arrays were used to define time series of cyclic stress ratios and shear strains throughout the profile. Cyclic resistance ratios against triggering of $\sim 100\%$ excess pore pressure ratio in 15 equivalent uniform cycles were computed at multiple depths based on weighting of the cyclic stress ratio time series up to the time of triggering. Cone penetration tests performed at select times during each model test were used to define the variation in cone tip resistances with depth and shaking history. The resulting data pairs, with normalized cone tip resistances ranging from 20 to 340 and cyclic resistance ratios ranging from 0.1 to 2.0, show that both quantities progressively increase as a result of recurrent liquefaction events and generally follow the trends predicted by case history–based liquefaction triggering correlations. Three 1-m-radius centrifuge tests of similar configurations produced consistent results. Implications for the interpretation of case histories and engineering practice are discussed.

This paper compares blasting damage depth in layered jointed basalt before and after grouting. First, a method of determining blasting damage depth in layered jointed basalt is proposed, with a thorough theoretical analysis, and the improvement effect of grouting on damage control in the layered jointed basalt is evaluated quantitatively. The results demonstrate that the reflected tensile stress transmitted back to the previous joint is the key factor for the occurrence of damage. Consolidation grouting could reduce damage depth by 15–35%. The spatial distribution of blasting damage in the layered jointed basalt is then predicted with numerical simulation using the commercial software LS-DYNA. Results reveal that the damage depth estimated based on numerical simulation matches well with that estimated based on the theoretical analysis. Two types of damage zones exist in the layered jointed basalt. Last, a field experiment was implemented to investigate blasting damage depth in layered jointed basalt before and after grouting based on an excavation of the Baihetan high rock slope. Results demonstrate that the depth and degree of damage of the layered jointed basalt were both larger than that of conventional basalt and that grouting could significantly reduce damage depth. The error between the experiment, theoretical calculations, and numerical simulation was within 10%.

Enzymes provide a nontoxic alternative to toxic products used in soil improvement and are economically attractive. For example, enzymes have been used in road construction to improve the durability of the base and the subbase of pavements. Would enzyme-treated soils exhibit higher resistance to erosion than untreated soils? That is the question. Erosion function apparatus (EFA) tests were conducted to provide an answer. The EFA is a laboratory device used to measure the erosion function of a soil defined as the relationship between the soil erosion rate and the water velocity or the water shear stress. In this study, three different types of enzymes were used to treat two different types of soils: a low-plasticity silt and a silty sand. For each sample, the selected water content was the optimum value from the Proctor compaction test. For each enzyme, two different concentrations and two different treatment periods were considered. The measured erodibility of the enzyme treated soils was compared with the measured erodibility of the untreated soils. The results showed that enzyme-treated soil samples exhibit higher resistance to erosion than untreated samples.

Tsunamis induce pore-water pressures in coastal soil beds, and understanding how tsunami-induced excess pore-water pressure gradients form is not straightforward given the loading timescale and seepage effects. This study develops a coupled seepage-deformation model to describe tsunami-induced pore-water pressure response in soil beds. The coupled seepage-deformation model is implemented using the finite-difference method, and numerical experimentation is performed on saturated soil beds using hypothetical tsunamis. The results imply the dependence of the tsunami-induced excess pore-water pressure head gradient on the tsunami water’s weight and compressibility of the pore water. The results imply the importance of modeling tsunami-induced deformation, the partial drainage condition, and pore-fluid condition when considering tsunami-induced pore-water pressures in soil beds.

Characterization studies conducted on Class-F fly-ash specimens gathered from different producers in the southeastern United States confirm general trends reported for fly ash worldwide. Additional tests and detailed analyses explain the spread in specific gravity (interparticle porosity cenospheres), highlight the tendency to segregation and layering, and show marked ferromagnetism. Furthermore, data show that early diagenetic cementation—within days after wetting—hinders densification and produces a fabric that is prone to collapse. New procedures are specifically developed to diagnose and characterize early diagenesis, including (1) pH measurements as an indicator of diagenetic potential, (2) test protocols to assess early diagenesis using oedometer tests and shear-wave velocity, and (3) procedures to determine realizable unit weights as reference values for the analyses of contractive or dilative tendencies and instability. In the absence of early diagenetic cementation, dilative fly-ash behavior is expected in the upper $\approx 20\mathrm{m}$ under monotonic shear loading. Flow instability may follow the failure of the containment structure if the ponded ash is saturated and has experienced hindered densification.

Cured-in-place linings (CIPLs) are flexible fiber-reinforced polymer linings used to rehabilitate aging pipelines in situ. They also can strengthen utilities against transient and permanent ground deformation caused by earthquakes, thus providing added value through seismic retrofitting. This paper presents the results of full-scale fault rupture tests to characterize the debonding, axial elongation, and bending performance of pipelines with circumferential cracks and weak joints strengthened with CIPLs and subjected to abrupt ground deformation. The results of finite-element simulations were compared with the experimental fault rupture response of jointed pipelines with and without CIPL reinforcement. The results of a numerical model that accounts for debonding between the lining and pipe as Mode II fracture propagation were in good agreement with full-scale fault rupture test results. Recommendations are made for applying the modeling and experimental results for in situ strengthening of underground utilities against earthquakes and other sources of permanent ground deformation.