Banner - Seawall Failure Across Different Coastal Environments

Seawall Failure Series – 2. Seawall Failure Across Different Coastal Environments

Admin September 28, 2023

The design, construction, and maintenance of seawalls that can withstand the ceaseless battering of marine forces are an ongoing challenge. These structures, while essential for safeguarding coastal assets and communities, are under perpetual siege by erosional processes, which can lead to catastrophic failures if not adequately addressed. The risks and complexities associated with seawall failure become magnified across diverse coastal terrains, where varying wave energy, sediment properties, and topographical features dictate the threats posed to the structural integrity of seawalls. The design, construction, and maintenance of seawalls that can withstand the relentless pounding of ocean waves present an ongoing challenge for engineers across a range of shoreline environments.

The Energy Equation: Wave Impact and Seawall Integrity

The energy imparted by waves onto seawalls stands as one of the primary drivers for both soil erosion and potential structural failure. The dynamics of this energy can vary considerably based on the coastal environment:

Open Ocean Coasts: Immense wave energy, propelled by long-fetch waves that traverse vast ocean coastlines, put constant pressure on seawalls in these areas. The direct impact of stormy coastal waves can cause immediate structural damage to seawalls, especially if their design lacks adequate energy dissipation mechanisms. Over time, repeated battering can lead to structural fatigue and failure.
Enclosed Bays or Lagoons: Here, the wave energy narrative is subtler. While direct wave impact might be lessened due to shorter fetches and natural barriers, other forces come into play. Tidal fluctuations and circulatory currents can induce water pressure differentials, potentially compromising the seawall’s structural integrity through the hydrostatic pressure it places on the soil from behind or below the structure.

Sediment Dynamics: From Support to Threat

The type of sediment underlying and surrounding a seawall directly influences its structural longevity. Each sediment type comes with its own set of challenges:

Sandy Coasts: The mobile nature of sandy sediments makes them vulnerable to being displaced by wave actions. For seawalls, this often results in the undermining of foundational structures, creating voids or pockets. Over time, these voids can lead to partial or complete seawall collapses.
Clay or Silty Coasts: While these sediments offer better cohesion, they can be prone to liquefaction, especially under specific wave or tidal conditions. Base failure or tilting is a risk if the supporting sediments suddenly lose their strength.
Rocky Coasts: On the surface, rocky terrains might seem impervious to erosional forces. However, the natural fissures and cracks in rocky substrates can allow water intrusion, which over time can weaken the seawall’s foundational grip, leading to potential structural compromises.

The Role of Coastal Topography in Seawall Stability

The physical contour of a coastline isn’t just an aesthetic feature—it has direct implications on how seawalls respond to marine forces:

Steep Coastlines: Such terrains can increase wave reflection, creating zones of turbulence near the seawall base. This turbulence can enhance forces that cause erosion, threatening the structural stability of the wall, especially if the protections are eroded or compromised.
Gently Sloping Coasts: The gradual gradient can disperse wave energy over a more extensive area, reducing direct wall impact. However, this also means a larger zone of wave-soil interaction, potentially leading to widespread undermining of the seawall’s foundational structures.
Irregular Coasts: Features such as coves, headlands, or peninsulas can induce wave refraction, concentrating wave energy onto specific segments of the seawall. This can lead to uneven structural stresses, with certain wall sections bearing disproportionate loads, heightening their failure risk.

The integrity of a seawall isn’t a mere reflection of its construction caliber. It’s a dynamic entity, deeply intertwined with the coastal environment it inhabits. Recognizing and understanding the multifaceted challenges posed by wave energy, sediment characteristics, and topographical intricacies is paramount for designing and repairing seawalls that can stand resilient against nature’s relentless forces.

Banner - Understanding the Mechanics of Seawall Failure

Seawall Failure Series – 1. Understanding the Mechanics of Seawall Failure

Admin September 26, 2023

Seawalls are continuously subjected to the relentless forces of nature. The integrity of these structures is challenged by the complex erosional processes and hydrostatic pressures they must withstand. Delving deep into the science underpinning seawall vulnerabilities provides invaluable insights for designing more resilient coastal protection systems. The enduring stability of seawalls is challenged by intricate physical processes.

Wave Action

Wave action stands at the forefront of erosional forces impacting seawalls. The dynamics of wave action on seawalls encompass several mechanisms:

Wave Impact and Reflection: As waves strike the seawall, they exert direct hydraulic forces, leading to potential structural stresses. Additionally, waves that reflect off the wall can interact with incoming waves, creating zones of turbulence and amplified hydrostatic pressures.
Wave Overtopping: In situations where waves breach the seawall’s crest, the overflow can lead to backside erosion or increased water pressures, further destabilizing the wall.
Wave Run-up and Drawdown: Waves that surge up the face of the seawall can induce a downward flow, termed “drawdown,” leading to scouring at the base of the wall – a primary cause for undermining and structural failure.

Tidal Movements

Tides, with their cyclical rise and fall, exert their own brand of stress on seawalls:

Tidal Erosion: Repeated tidal inundation can gradually erode the seawall’s foundational structures, especially if there are sedimentary voids or weaknesses that water can exploit.
Hydrostatic Pressures: As the tide rises, the hydrostatic pressure on the wall will decrease due to the pressure on the landward and waterside equalizing with the water level rising. When the tide recedes, the hydrostatic pressure will increase dramatically, particularly if the wall has limited drainage. This is due to the extended time it takes for the water on the landward to escape from the wall. Allowing the water to drain properly and at a faster rate will decrease the hydrostatic pressure.

Erosion

Erosion can manifest in various forms, each presenting unique challenges:

Toe Erosion: The base or “toe” of the seawall, being in constant contact with both water and sediment, is highly susceptible to erosion. As sediments are displaced, voids form, compromising the wall’s stability.
Rear Erosion: This is often a consequence of wave overtopping or poor drainage. Water accumulating behind the wall can lead to soil erosion, creating pockets or channels that undermine the wall’s structural integrity.
Seepage Erosion: Groundwater or trapped water behind the wall can seep through porous materials or cracks, mobilizing sediments and leading to internal erosion pathways.

Hydrostatic Pressure

Hydrostatic pressure, the force exerted by fluids in response to gravitational forces, can be particularly detrimental to seawalls:

Pressure Build-up: Poor drainage or impermeable backfill materials can cause water to accumulate behind the seawall, increasing hydrostatic pressures. This pressure can push against the wall, straining its structural integrity.
Pressure Oscillations: Rapid changes in water levels, be it from waves or tides, can induce oscillatory hydrostatic pressures, which cyclically load and unload the seawall, leading to material fatigue over time.

A symphony of forces challenges the durability of seawalls. Understanding the multifaceted mechanics of wave action, tidal influences, erosion, and hydrostatic pressures is pivotal for evolving engineering strategies, practices, and solutions. Only through a comprehensive grasp of these dynamics can we aspire to design and repair seawalls that not only stand firm against nature’s onslaught but also thrive amidst its challenges.

Seawall Damage – Fix It or Replace It?

Admin August 22, 2023

Causes and Signs of Seawall Failure

Seawalls play a critical role in protecting coastal properties from erosion, storm surges, and other natural forces. However, over time, these structures can face various challenges that may compromise their effectiveness. Seawalls can fail due to a variety of factors, including natural forces, structural degradation, and poor construction. Here are potential ways a seawall can fail and how you can identify the signs and symptoms that might indicate the need for repair or replacement…

Erosion and Undermining

Failure: Gradual erosion of the soil behind the seawall can weaken its foundation, causing it to sink or collapse.
Signs and Symptoms: Visible subsidence of the seawall, soil erosion around the base, cracking or tilting of the seawall, or water seeping through gaps.

Wave Overtopping

Failure: Waves exceeding the height of the seawall can wash over it, eroding the soil behind it and compromising its effectiveness.
Signs and Symptoms: Frequent wave overtopping during storms, water damage to structures behind the seawall, or weakened soil along the wall’s backside.

Corrosion and Deterioration

Failure: Exposure to salt water and environmental conditions can lead to corrosion and deterioration of the materials, weakening the seawall’s structural integrity.
Signs and Symptoms: Rust or corrosion on metal components, visible deterioration of concrete or masonry, cracks, chips, or spalling.

Foundation Settlement

Failure: Uneven settling of the seawall’s foundation can result in structural instability and cracking.
Signs and Symptoms: Visible cracks in the seawall, differential settlement causing tilting or sinking, or gaps forming between the wall and the ground.

Seepage and Water Infiltration

Failure: Water seeping through cracks or gaps in the seawall can erode the soil behind it and compromise its stability.
Signs and Symptoms: Ongoing water seepage through the seawall, soil erosion behind the wall, or signs of water damage on the landward side.

Aging and Wear

Failure: Over time, the materials of the seawall may degrade naturally, reducing its strength and stability.
Signs and Symptoms: Visible signs of wear, weathering, or aging such as fading, cracking, or crumbling.

Infrequent Maintenance

Failure: Lack of regular maintenance can allow minor issues to escalate into major problems.
Signs and Symptoms: Accumulation of debris, vegetation growth, or the presence of visible damage that has gone unaddressed.

Environmental Changes

Failure: Changes in water levels, storm frequency, or coastal processes can lead to unexpected stress on the seawall.
Signs and Symptoms: Frequent storm damage, shoreline retreat, or increased susceptibility to erosion.

Regular inspections and prompt action in response to any of these signs are crucial to preventing seawall failures and ensuring the safety of coastal properties. We recommend at least an inspection by either yourself or a qualified professional from our network on a yearly basis.

Repair or Replacement?

Repairing a seawall using polyurethane grouting and soil stabilization is often considered when the damage is not extensive, and the structural integrity of the seawall can be effectively restored. However, the decision to repair versus replace a seawall depends on several factors. When trying to determine whether to repair or replace, consider these factors…

Seawall Repair

Cracks and Gaps: If the seawall has visible cracks, gaps, or voids, Seawall Repair Network®’s SW-RP1 can be effective in filling these voids and stabilizing the soil behind the seawall.
Erosion: When erosion is apparent in specific areas and the majority of the seawall structure is intact, the repair process can stabilize the soil and prevent further erosion.
Structural Stability: If the seawall’s structural integrity is still intact and it’s not at risk of imminent collapse, repair material can be used to reinforce and strengthen the existing structure.
Cost-Effectiveness: Repairing with the seawall stabilization process is more cost-effective (typically 90% less than the cost of replacement).

Seawall Replacement (Too Damaged for Repair)

Extensive Structural Damage: If the seawall has extensive structural damage such as widespread cracking, severe tilting, or signs of imminent collapse, it might be beyond the point of effective repair.
Foundation Instability: If the foundation of the seawall has suffered significant settlement or shifting, it could compromise the structural stability even after repair attempts.
Corrosion and Deterioration: If the seawall’s materials are severely corroded, deteriorated, or weakened, repair efforts might not provide a long-lasting solution.
Changes in Environmental Conditions: If the coastal environment has changed significantly, such as increased storm frequency or rising sea levels, the seawall might need to be replaced to better withstand these new conditions.

Ultimately, the decision to repair or replace a seawall should be made after a thorough assessment by a Seawall Repair Network® preferred marine contractor. Each network member has been trained to evaluate the extent of the damage, and the potential effectiveness of repair methods, and to offer a long-term sustainable solution. In some cases, a hybrid approach might be taken, where damaged sections are repaired while severely compromised sections are replaced.

Seawall Erosion Control

Admin July 25, 2023

Seawall Erosion Control – Soil Stabilization

Seawalls are important structures that protect waterfront property from erosion and flooding. However, seawalls can deteriorate over time due to a variety of factors, including weathering, wave action, and soil erosion. When a seawall begins to show signs of damage, it is important to repair it as soon as possible to prevent further deterioration and protect your property. Soil erosion is often a key factor in seawall failure. Seawalls depend on supporting soil for structural support. Contractors using SW-RP1 seawall repair material can stabilize surrounding soil, repairing leaking cracks in the process. This process permanently strengthens and repairs soil damage and prevents future erosion.

Additional Seawall Erosion Control Methods

The installation of a hydrostatic pressure control system, which automatically removes any future water that builds up behind the seawall. Unchecked water build-up causes hydrostatic pressure which cracks and damages even the strongest seawalls.
Seawall cap repair with high-strength epoxy and concrete repair materials. This process addresses surface cracks on top of the seawall and restores strength and integrity to the structure.
If necessary, the installation of a seawall anchoring system. When needed, steel tie-backs are installed to prevent future movement of the seawall in high-risk sections. The tie-backs lock into load-bearing solid soil behind the wall.

Seawall Erosion Control Contractors

Seawall erosion control is an art and a science, best performed by preferred marine contractors who have been thoroughly trained in the latest and most effective repair methods.

Common Causes of Seawall Failure

Admin June 20, 2023

Seawalls typically fail prematurely due to a couple of common causes. One of the main causes of seawall failure is soil migration, which can destabilize the entire structure. Another cause is hydrostatic pressure buildup on the landward side, which often contributes to soil migration.

Soil Migration and Seawall Failure

Soil migration is the movement of soil from one location to another due to various factors such as waves, tides, and storms. This can cause erosion at the base of the seawall, undermining its stability. In addition, soil migration can lead to the formation of voids or empty spaces behind the seawall, which can cause further destabilization. Void formations can occur when soil is washed away from behind the seawall, creating a space between the seawall and the ground. These voids can undermine the integrity of the structure, increasing the risk of failure. Soils that are not sufficiently compact or stable are more prone to erosion and void formation.

Hydrostatic Pressure and Seawall Failure

Hydrostatic pressure is the pressure exerted by a fluid, such as water, on a structure. When there is a buildup of hydrostatic pressure on the landward side of a seawall, it can cause the structure to become unstable and potentially fail. This water buildup can be caused by a variety of factors, such as high tides, waves, and storms. The effects of hydrostatic pressure buildup on the landward side of a seawall can be significant. It can cause the seawall to tilt or lean, increasing the risk of failure. In addition, the added pressure can cause the seawall to crack or break, leading to further destabilization.

Preventing Seawall Failure

To prevent premature failure of a seawall due to soil migration and void formation or hydrostatic pressure buildup, it is important to have a professional evaluate the condition and stability of the structure. If necessary, the supporting soil and the structure can be stabilized, and a hydrostatic pressure release system can be installed to prevent undue pressure on the wall.

How Freeze/Thaw Cycles Destabilize Seawalls

Admin March 27, 2023

What are Freeze/Thaw Cycles?

A freeze/thaw cycle is completed when soil freezes in cold weather and then thaws out again in warm weather. This cycle loosens up and destabilizes soil over time. This process causes erosion and can be problematic for structures that depend on supporting soil.

How Do Freeze/Thaw Cycles Damage Seawalls?

A healthy seawall has strong supporting soil on the landward side. The freezing and thawing process causes soil to become soft and less compact. Shifting and eroding supporting soil can cause cracks, movement, and leaks. Once these signs of distress appear, the “cost” clock starts ticking. The longer they are ignored, the more expensive the eventual repair or replacement.

Repair Seawall Damage Caused By Freeze/Thaw Cycles

Soil that has been permeated with SW-RP1 repair material is typically less infiltrated with moisture and thus less subject to erosion caused by freezing and thawing. Depending on the soil type, this procedure could prevent frost heave altogether. The Seawall Repair Network® proprietary repair process stabilizes the supporting soil while sealing cracks and leaks in the structure at the same time.

Water is Relentless!

Admin December 12, 2022

Water is relentless. This is a key fact that all waterfront property owners should thoroughly understand. The price of enjoying an oceanfront, riverfront, or lakeside view from the comfort of your own home is the inherent risk that comes with living right next to a large body of water.

Four Critical Warning Signs of Seawall Failure

If your residence is protected by a seawall, you should familiarize yourself with the four critical warning signs of seawall failure:

Soil Depressions Near the Seawall
Rust Stains on the Surface
Movement or Shifting of the Seawall
Cracks in the Concrete

Excessive rainwater or floodwater build-up on the landward side of the wall (usually resulting from an inadequate or clogged weep hole system within the wall itself) will put untenable hydrostatic pressure on the structure. This pressure can cause parts of the wall to move and/or crack. Once the concrete is broken, landward side water will pull soil from your property through the wall and into the water on the other side, causing depressions or small sinkholes near the structure. In addition, steel rebar or mesh inside the wall is exposed to rust, resulting in rust stains appearing on the surface.

Four Options for Dealing with Seawall Damage

Once aware of these problems, you’re faced with four options:

Ignore the Problem and Do Nothing
(If you go this route, the problem gets worse – and more expensive to repair – over time.)
Replace the Seawall
(This option is typically a lot more expensive than a repair, requires heavy equipment, and involves messy disruptive excavation.)
Repair with Inferior Methods
(Inferior repair materials such as hydraulic cement, slurry, and sodium silicate do not provide a permanent, long-term solution.)
Repair with proven Seawall Repair Network^® methods.
(More on this in the next section.)

You can read more about these four options on the Seawall & Bulkhead Replacement vs Repair page. Needless to say, any of the four critical warning signs should warrant a checkup from a qualified seawall repair contractor. Most contractors offer free professional assessments and repair estimates.

Fortunately, there are many effective methods at your disposal in the battle against water’s relentless onslaught. Seawall Repair Network^® preferred marine contractors provide two major types of repair – seawall stabilization and seawall preservation.

Seawall Stabilization

Stabilizing a cracked or shifting seawall is accomplished via these four methods:

Stabilizing Soil and Sealing Leaks with SW-RP1
(SW-RP1 repair material is stronger than crystalline bedrock and safe for the environment.)
Installing a Hydrostatic Pressure Control System
(Creation of pressure release channels with filters that allow water to move back and forth, maintaining an equilibrium of hydrostatic pressure. These filters also prevent soil migration and void formation on the landward side.)
Repairing Cracks in Seawall Caps
(Repairing the seawall caps with high-strength epoxy.)
Installing a Seawall Anchoring System – If Necessary
(When needed, steel tie-backs are installed to prevent future movement of the seawall.)

You can learn more about these methods on the Seawall Stabilization page.

Seawall Preservation

Treating the concrete with preservation solutions provides additional long-term protection. Preservation is accomplished via these three methods:

Inhibiting Corrosion with SW-Prevent
(SW-Prevent creates an insulating layer on the surface of any steel rebar or mesh inside the wall.)
Strengthening Surface Concrete with SW-Power
(SW-Power renders concrete surfaces resistant to air or water-born chemical damage.)
Protecting Surface Concrete with SW-Protect
(SW-Protect inhibits water penetration.)

You can learn more about these methods on the Seawall Preservation page.

Water is Relentless – But YOU Can Be Too!

There is no reason to be intimidated by water’s relentless onslaught. All you have to do is memorize the four critical warning signs, and then enlist a qualified seawall repair contractor when needed. With the proper stabilization and preservation support, your seawall can safely protect that beautiful waterfront view for generations to come.

Bulkhead / Seawall Repair in Buffalo, New York

Admin August 22, 2022

Waterfront property owners in Buffalo, New York face yearly challenges due to the sometimes turbulent nature of Lake Erie. This immense body of water is capable of producing wave activity similar to hurricane conditions.

One of the great challenges associated with Lake Erie is the build-up of hydrostatic pressure on the landward side of the seawall.

As mentioned in the previous blog post, What Hydro-Static Pressure Is and Why Seawall Owners Should Be Concerned…

Hydrostatic Pressure is most commonly defined as the pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above.

Hydrostatic pressure builds exponentially when groundwater “stacks up” behind a seawall. Water (and all liquids in general) gravitates to level with the existing water table. Water will always follow the path of least resistance. This force causes movement within unstable soil.

The great news for waterfront property owners (who rely on their seawalls, bulkheads, and revetments to protect their property from nature’s forces of devastation) is that the Seawall Repair Network’s proprietary repair process protects these same structures from failure.

In the picture included with this article, the seawall on the left side has been protected with the Seawall Repair Network materials, equipment, and installation procedures. Unfortunately, the seawall in the background on the right side has not, and the structure is now destabilized and moving forward. If left unprotected, the seawall on the right side will fail.

Seawall Repair Network Member Mike Garnett of Garnett Seawall Solutions utilized the proprietary repair process to ensure that hydrostatic pressure would not cause the above seawall to move and fail.

The customer was highly satisfied with the work accomplished by Garnett Seawall Solutions and referred them to many other neighbors in the area.

Seawall Repair Network’s Patent-Pending Process

Admin November 23, 2021

Mother Nature’s oceans, lakes, and rivers can be so beautiful and calm. But over time, her natural forces will cause damage and eventual failure of your seawall. Seawalls are complicated structures made up of a variety of essential components. If one component fails, the entire seawall is at risk. In traditionally constructed seawalls, weep holes with a geotextile fabric filter allow water to flow from the landward side back into the ocean to prevent pressure build-up.

What Causes Seawall Failure?

What causes your seawall to fail? Over time, as the filter fabric fails, soil migration creates voids behind the wall, which causes structural instability. As the voids behind the wall fill up with water, hydrostatic pressure behind the seawall causes the wall panels to shift over time. The shifting panels damage the seawall cap, which holds the entire structure together. When this happens, failure of the seawall is imminent. If ignored, these problems only get worse.

Seawall Stabilization Repair Process

Water is RELENTLESS. But YOU can be too! Professionally trained contractors, armed with Seawall Repair Network’s patent-pending repair process, are ready to guide you to victory in this battle!

Watch the video below for a complete explanation of Seawall Repair Networks seawall stabilization process.

How Soil Instability Causes Seawall Damage

Admin June 9, 2021

Erosion and Soil Loss (Void Formation – Landward Side)

Causation: As seawalls age, soil eventually starts to migrate through the vertical seawall panel joints and weep holes. At the time of original seawall construction, a geotextile filter fabric is installed on the landward side along the panel vertical joints and weep holes. Filter fabric serves the critical function of preventing soil loss into the waterway from the landward side.

An essential point to remember is that seawalls are designed to keep the land in more than to keep the water out. Seawall structures are engineered to allow water to pass through seawall vertical panel joints and weep holes. The engineering concept Equilibrium of Hydrostatic Pressure refers to neutralizing opposing forces caused by water pressure on both the landward side and the opposing waterward side of the seawall structure.

Over time, all filter fabric begins to deteriorate and become ineffective. Once this occurs, soil migration begins to occur during every water event (rain, irrigation, daily tide activity, storm surge, etc.). A slow process initially, soil migration leads to void formations on the landward side of the seawall. Void formations immediately begin to jeopardize the overall stability of the seawall structure. The loss of structural stability leads to unwanted movement of the structure. As the movement of the structure occurs, damage to the seawall cap and panels also occurs, and stress on the seawall tie-rods and deadman anchors will lead to damage or sometimes complete failure of the overall seawall structure.

The Domino Effect (How Soil Instability Causes Seawall Damage)

When considering the relationship between the various causes of seawall damage, simply think of the domino effect in order to clarify the complexities associated with seawall engineering:

Natural forces create a domino effect which causes seawall damage and eventually seawall failure if not mitigated and remedied in time:

Erosion due to filter fabric deterioration leads to…
Void formations behind the seawall, which lead to…
Deterioration of the seawall berm (or supporting soil) leads to…
A build-up of hydrostatic pressure behind the seawall, which leads to…
Damage to seawall the cap, seawall panels, and anchor system, which leads to…
De-stabilization of the entire seawall structure, which leads to…
Seawall failure, which leads to…
Financial loss, wasted time, destruction of property, and STRESS.

Has your seawall been damaged by natural forces? Click the button below to download an info-packed guide to permanent and lasting repair.