Roadway design in Des Moines must address the region’s glacial till and loess-derived subgrades, which are highly susceptible to moisture-induced volume changes and frost heave under Iowa DOT Standard Specifications. A reliable pavement section starts with a thorough geotechnical evaluation to match structural requirements to local soil behavior. This often involves a flexible pavement design that accommodates subgrade movement, or a rigid pavement design where higher stiffness and durability are required for urban arterials.
Commercial site access roads, residential subdivisions, and arterial widening projects all demand laboratory verification of subgrade strength before finalizing thickness. A CBR study for road design provides the soaked strength values needed to calibrate both empirical and mechanistic-empirical sections per AASHTO guidelines, ensuring the finished roadway resists rutting and cracking through Iowa’s freeze-thaw cycles.
Design of active prestressed anchors for soldier pile and lagging walls, secant pile walls, and diaphragm walls. Includes bond length calculations, tendon selection, and staged testing specifications for Des Moines glacial till conditions.
Passive ground anchors and soil nail arrays for permanent slope stabilization and temporary excavation support. Grout-to-ground bond stress verified through field pull-out tests, with corrosion protection tailored to project design life.
FHWA-NHI-10-024: Soil Nail Walls, FHWA-NHI-10-025: Ground Anchors and Anchored Systems, AASHTO LRFD Bridge Design Specs, Section 11, PTI DC35.1: Recommendations for Prestressed Rock and Soil Anchors, ASCE 7-22: Minimum Design Loads for Buildings
Prestressed active anchors generally perform better in stiff, overconsolidated till because they limit initial movement and allow verification of capacity through proof testing. Passive anchors can work for temporary applications but require careful evaluation of creep potential when the till is saturated. The bond zone should be positioned in the till unit below any surficial sand or fill layers.
Anchor design packages typically range from US$1,080 to US$3,230 depending on wall height, number of anchor rows, and whether permanent corrosion protection is required. This covers design calculations, construction drawings, and testing specifications.
ASTM A416 specifies tendon requirements. On site, we require proof tests at 133% of design load and creep tests lasting 10 to 60 minutes at lock-off load. For critical permanent anchors, extended creep testing and lift-off checks after lock-off are standard practice to confirm long-term performance in Iowa's glacial soils.
Yes, but groundwater is the controlling factor. Alluvial sands near the river are permeable and can cause grout loss during installation. We design for fully grouted bond zones using tremie methods and specify watertight corrosion protection. Anchor free lengths are extended to place the bond zone in competent till or shale below the river valley deposits.