Construction and demolition (C&D) waste has become a research hotspot due to the need for environmental sustainability and strength enhancement of cementitious materials. However, wider applications of C&D waste are limited, as its non-homogeneous surface nature limits its workability. This research evaluated the feasible utilization of C&D waste as aggregates in polypropylene-fiber-reinforced cement-stabilized soil (CSS) under sulfate-alkali activation. CSS specimens incorporated Portland cement and C&D waste in 10%, 20%, and 30% proportions. Also, polypropylene fiber after alkali activation by sodium sulfate (at 0.2%, 0.4%, and 0.8% dosing level) was defined as 1%, 2%, and 4%. Strength enhancement was examined through unconfined compressive strength (UCS) and flexural strength tests at 7, 14 and 28 days. Test results indicated that mechanical properties showed significant improvement with increasing levels of Portland cement and sodium sulfate, while the improvement dropped after excessive addition of C&D waste and polypropylene fiber. Optimal proportioning was determined as 30%, 4%, 20%, and 0.8% for Portland cement, polypropylene fiber, C&D waste, and sodium sulfate, respectively. Scanning electron microscope (SEM) analysis attributed the enhancement to hydration product (ettringite) formation, bridging effect and increased particle friction. Additionally, the decrease in amplification was ascribed to the destruction of interface transition-zone (ITZ) strength, resulting in premature failure.

Anchoring force loss is critically concerned for the in-service performance of prestressed ground anchors. This time-dependent loss of pretension exerted at the anchor head is caused primarily by stress relaxation, which integrally manifests the rheological properties of the anchor and the geomaterial in which the anchor is embedded. A load-transfer modeling framework was established to derive the time-dependent anchoring force response. The modeling parameters were directly calibrated via element-scale pullout stress relaxation test using a specially developed setup. The applicability and effectiveness of this analytical modeling framework were verified via large-scale laboratory model tests and in situ tests of prestressed anchors. The predictions derived using the presented modeling framework were in good agreement with measurements in both laboratory model tests and in situ tests, particularly for evolutions of anchoring force over time. Sensitivity evaluation of the model parameters was performed to study their respective impact on the anchoring force loss response. This work can provide insights into the understanding of the anchoring force loss behavior of prestressed ground anchors and facilitate their design practice for in-service performance.

The performance of soil nail systems relies primarily on soil-nail interaction, which is especially complex for nails embedded in clay materials. Soil-nail interaction is difficult to predict in these soils because of the effect of moisture-induced stress and swelling along the interface between soil and nail. As part of this investigation, tests were conducted to characterize the soil-nail interface shearing mechanisms using a novel element nail pullout device that involves comparatively short nails embedded in soils under varying degrees of saturation. Additionally, a large-scale pullout test, involving inundation and loading phases, was conducted using soil nails embedded in expansive clays. The soil-nail interface shearing mechanisms identified with the element nail pullout device and the vertical rise measurements of the clay from the inundation test were used within a load transfer theoretical framework aimed at predicting the response of soil nails in expansive clays. This load transfer framework provided a very good prediction of the large-scale pullout test results using the data collected from the element nail pullout tests.