This study explores an innovative application of ultra-high-performance concrete (UHPC) by partially substituting cement with nano-zirconia (NZ) and micro-zirconia (MZ). A series of experiments were conducted to explore the influence of zirconia particle size (3860 nm and 320 nm) and varying replacement levels (0%, 0.5%, 1%, and 1.5%) on the workability, mechanical behavior, and microstructural characteristics of UHPC, utilizing the particle packing density model as a basis. Findings reveal that replacing 0.5% of the cement with MZ and NZ results in workability and mechanical performance comparable to the control mix. However, at 1.5 wt% MZ and 1.5 wt% NZ substitution levels, flowability declines by 22.01% and 24.71%, respectively, accompanied by a substantial increase in viscosity. The wet packing density of UHPC exhibits a linear rise with increasing zirconia content, with nano-sized particles exerting a more pronounced effect than their micro-sized counterparts. Specifically, at a 0.5% MZ replacement level, the 28-day compressive and flexural strengths show marginal improvements of 1.82% and 4.48%, respectively. The NZ1MZ0.5 mix achieves the highest 28-day compressive strength increase, reaching 9.45%, with an absolute gain of 11.92 MPa. Analyses using XRD, FTIR, and thermogravimetric analysis (TGA) demonstrate that zirconia incorporation has a negligible influence on the hydration process and does not alter the composition of hydration products in N-UHPC. Although zirconia effectively reduces porosity, excessive amounts (1.5%) increase pore size within the cement matrix, ultimately compromising mechanical properties. Based on these findings, the optimal NZ dosage for UHPC, when used in combination with MZ, is determined to be 0.5%.

In recent years, rectangular pipe jacking technology has been gradually applied in urban underground engineering. Based on a parallel rectangular pipe jacking project, a three-dimensional finite element model is established for numerical analysis, and the surface settlement caused by rectangular pipe jacking construction is studied. The research shows that the pipe jacking construction has the most obvious impact on the soil above the pipe jacking axis, and when the clear distance between parallel rectangular pipe is 1D (D indicates the pipe inner width), the main influence range of pipe jacking construction on soil mass is about 1D along the longitudinal direction of pipe jacking. With the increase of parallel rectangular pipe distance, the surface settlement trough becomes wider and the maximum surface settlement decreases. The main influence range of parallel rectangular pipe jacking construction at the outside of the pipe jacking is about 1D~1.37D along the lateral direction. When the pipe distance is greater than 2D, the interaction between parallel pipe jacking is weak, and the influence range at the outside of pipe jacking is almost the same as that of single pipe jacking construction. The research results can provide a reference for the design and construction of similar pipe jacking projects.

The Surface Water and Ocean Topography (SWOT) mission provides reservoir water surface elevation (WSE), but converting absolute WSE to storage remains sensitive to the relative reference and shape of hypsometric curves. Here, we evaluate a site-specific vertical alignment parameter and a hydrostatic-constrained extension for truncated hypsometric curves using 14 reservoirs with concurrent in-situ records and two hypsometric curves: GRDL (Global reservoir dataset through deep learning) and REGEOM (geometric approximation). Under the reference assumption that the maximum observed SWOT WSE corresponds to full capacity, the median capacity-normalized root mean square error (RMSE) is 14.9%. The reservoir-specific full-record calibration reduces this value to 2.9%, showing that effective vertical alignment is a major sensitivity. GRDL yields lower capacity-normalized RMSE than REGEOM. Artificial-truncation experiments show that the constrained extension reproduces withheld portions of tabulated curves with median reconstruction errors below 1% across the tested distances. A chronological 60/40 holdout test supports temporal generalization after local calibration: for the 11 reservoirs, the median capacity-normalized RMSE is 0.026 in both calibration and validation periods. In contrast, leave-one-reservoir-out tests find no statistically significant improvement over the reference assumption. The results therefore support locally calibrated, sampled storage retrieval while showing that transfer of a single alignment parameter to fully ungauged reservoirs remains unresolved.

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