Before engineers choose pavement materials or calculate thickness, they start with the most important part of any roadway: the soil beneath it. Across Texas, Oklahoma, New Mexico, and Colorado, soil conditions can change dramatically from one project to the next — and those differences directly impact how roads are designed, built, and maintained.

When engineers understand how a soil behaves under load and moisture, they can design pavements that last. When they don’t, even a well-built road can start cracking, settling, or rutting long before it should.

Why Soil Matters So Much

The soil under the pavement (the subgrade) supports every layer above it. If that soil is weak, sensitive to moisture, or prone to movement, the pavement will eventually reflect that:

• Cracks form
  
• Ruts develop
  
• Edges break down
  
• Sections settle or shift

Good pavement design always starts with good geotechnical information.

A Region With Every Soil Type You Can Imagine

The Southwest includes everything from expansive clays to loose sands to frost-prone soils — sometimes all within a short distance.

Texas

Texas has some of the most varied soils in the country:

• East/Central Texas: expansive clays with high plasticity

• West Texas & New Mexico border: playa clays, sands, and caliche

• South Texas: moisture-sensitive silts

Even though expansive clay is more common in east and south Texas, certain playa regions in West Texas still require careful design to prevent movement.

Oklahoma

Oklahoma sees clay-heavy soils, silts, and moisture-sensitive subgrades that soften when wet, making stabilization a common part of roadway design.

New Mexico

New Mexico has collapsible sands, silts, and caliche layers. These materials usually require lime or cement treatment to improve strength.

Colorado

Colorado adds freeze–thaw cycles and frost-susceptible soils into the mix, which can cause heaving if water gets trapped beneath pavement.

How Engineers Evaluate Soil

Before pavement design begins, engineers collect geotechnical data through:

• Soil borings
  
• Lab testing
  
• Moisture and density measurements
  
• Plasticity (Atterberg limits)
  
• CBR or resilient modulus testing
  

This helps determine:

• Pavement thickness
  
• Whether stabilization is required
  
• The right base material
  
• What drainage improvements are needed

Good soil information prevents costly failure later.

Common Soil-Related Pavement Problems

1. Expansive or High-Plasticity Clays

These soils swell when wet and shrink when dry. Engineers often use lime stabilization, moisture barriers, or thicker pavement sections to manage movement.

2. Loose Sands

Common in New Mexico and parts of West Texas. Without stabilization or geogrids, sands can shift under traffic.

3. Frost-Susceptible Soils

In Colorado and northern Oklahoma, freeze–thaw cycles can push pavement upward and leave voids beneath it.

4. Moisture-Sensitive Silts

Silts lose strength quickly when wet, which can cause rutting or structural failure if not properly treated.

Designing Pavements That Work With the Soil, Not Against It

Once engineers understand the soil conditions, they select pavement structures that respond to those conditions — not ignore them. That might include:

• Flexible pavements that distribute load
  
• Rigid concrete sections for weak subgrades
  
• Subgrade stabilization (lime, cement, fly ash)
  
• Stronger base layers
  
• Drainage improvements to control moisture

There’s no one “right” pavement design. The right solution depends entirely on the soil.

Why Soil Stabilization Is So Common in the Southwest

Because the region has so many challenging soils, stabilization is often more cost-effective than replacing or overbuilding the subgrade. Engineers may use:

• Lime for high-plasticity clays
  
• Cement for sands or silts
  
• Geogrids to improve support
  
• Cement-treated base (CTB) for added stiffness

Stabilization increases strength and improves the road’s long-term reliability.

A Strong Road Starts With a Strong Subgrade

Pavement failures almost always trace back to soil conditions. When engineers understand the ground they’re working with and design around it, roads last longer, cost less to maintain, and perform better under traffic.

Centerline’s geotechnical and civil engineering teams work throughout Texas, Oklahoma, New Mexico, and Colorado to bring soil science and pavement design together in a way that supports safer, longer-lasting roads.

Learn more about our Civil Engineering Services (https://thecenterline.com/civil-engineering) or reach out through our Contact Page (https://thecenterline.com/contact/) if you’d like to discuss a project.

FAQs

Which soil conditions create the biggest issues?
High-plasticity clays, loose sands, moisture-sensitive silts, and frost-prone soils typically cause the most problems.

Can poor soils cause early pavement failure?
Yes. Weak soils lead to cracking, rutting, potholes, and settlement if not stabilized or reinforced properly.

How does soil testing affect pavement design?
It determines pavement thickness, stabilization needs, and what materials are required for long-term performance.

Can soils be improved for road construction?
Yes. Stabilization methods like lime, cement, geogrids, and drainage enhancements often make poor soils workable.