What is the proper vinyl sheet pile driving method for different soil types?

“Pitch and drive” method is the most practical way of pile driving in loose soils especially when using short piles. Also called “set and drive”, this method installs piles one by one. However, with only one interlock in control, sheet piles have high tendencies of rotating from the axis and leaning forward or backward. Panel driving is recommended for the dense deposit of sands and compact cohesive soils such as heavy clay or in presence of obstructions. In this method, a number of piles are interlocked together before driving. The panel of piles is supported by guide frames and driven gradually in sequence, sometimes in a staggered manner. The method can achieve installations of longer piles in more difficult ground conditions with better results in sheet pile alignment and verticality. In cases of difficult ground conditions such as hard strata and the presence of obstructions, driving assistance is employed along with a proper selection of driving method and equipment. Jetting and drilling help by loosening or eliminating obstructions by creating pressure right under the tip of the sheet pile being driven. Long and slender PVC sheet piles require steel mandrels as supports when driven in such conditions. Mandrel, which shape is similar to sheet pile profiles, increases the rigidity of Plastic Sheet Pile and supports the weight of the driving equipment such as a vibro-hammer.

What is the proper machine to drive piles in different conditions?

Impact driving is suitable for all soil types but appears to create the highest degree of stress to sheet piles. It is more appropriate to cohesive soils and soft soils such as silts and peats, loose medium to coarse sand, and gravels free of rock inclusions. Drop hammers such as the hydraulic hammer are the common types of impact-driving machinery. Driving using vibratory hammers is ideal for non-cohesive or granular soils such as soft soils and round-grained sand or gravel. It has also shown satisfactory performance in sandy, silty, or softer clay soils. It is less effective in angular-grained materials and soils with a firm consistency. With the introduction of vibration, however, the sub-soil can be further compacted, increasing penetration resistance and ultimately-refusal. If this is the case, driving aids like jetting and drilling might be necessary.

What are the pvc sheet pile selection criteria for soil condition of different hardness?

General rule of the thumb: “the harder the soil, the stronger and stiffer sheet pile section should be used”. Driveability of a pile section is a consequence of its cross-sectional properties (thickness, depth, and width), designed shape, length, grade, and the applied load. Hardness of soil strata characterized by SPT or CPT values is used to predict soil resistance which is essential in the calculation of driving force to be applied. Knowing the range of force from the selected driving machine, corresponding sheet pile sections can be picked according to their yield strength and elastic modulus.

How should I choose a sheet pile section for soils with, say, SPT Value, N=30? Can I still consider using vinyl or shift to steel?

Every sheet pile material has a design purpose, strengths, and areas of improvement. The availability of different materials denotes the need for a special material for a specific application. Plastic or synthetic sheet piles for example are known for being light and corrosion-resistant; Steel sheet piles are recognized for their extraordinary strength and versatility; and so on.

Feb 20, 20224 min read

Maintenance and Management of Marine Rubber Fenders

Marine fenders or rubber fenders are installed as protective equipment to ensure vessels' safe and smooth berthing and reduce or avoid damages to vessels & marine structures in waters and mooring facilities. To use these facilities as a high-quality infrastructure that serves its daily purpose, proper maintenance is essential, primarily to its appurtenances.

Because of constant exposure to harsh conditions, rubber fenders should be maintained and managed in a planned and appropriate manner to sustain their designed service life. To protect assets, including people's safety, optimum performance of marine fenders should be enhanced by avoiding the occurrence of damages and unintended rate of deterioration and ageing.

Maintenance and management should incorporate systems that effectively detects the deterioration of rubber fenders' damage, facilitate technical evaluation, and provide appropriate counter-measures. Basically, it has to contain a comprehensive matrix of the scope, timing, frequency, and methods of checks, diagnoses, and corresponding corrective actions.

Understanding Rubber Fenders by Classification

Assuming that impact is the main deteriorating factors for rubber fenders, it is important to understand the behavior of each kind and classify them according to how they absorb energy from berthing vessels.

V-type rubber fender- also known as arch fender. The fender body is the resisting mechanism itself and absorbs the berthing energy of the vessel by buckling and deformation of its body. Therefore, it is straight forward to pay attention to signs of deterioration at the rubber body due to external force.

Rubber fender with panels – similar types are cell fender and cone fender. A steel panel with resin pads such as UHMW PE, mounted at the rubber fender body, initiates the contact from berthing vessels and transfer the impact to the rubber fender which absorbs the energy by buckling deformation. Since the vessel does not come in direct contact with the rubber, the damage and breakage of the rubber body is minimal, care must be taken for the corrosion and deformation of the steel fender panel.

Pneumatic fender – absorbs the energy of the berthing vessel by its highly elastic features due to the compressed air pumped into the body - fabric-reinforced rubber bag. Floating air fender is generally protected by a net, so damage and breakage of the rubber main body is slight, deterioration of the net is more susceptible. Fixed air fender with a fender panel behaves similarly to a rubber fender with panel, and attention must be paid to the corrosion and deformation of the steel.

For both floating and fixed type, it is necessary to maintain the air pressure for maximum efficiency.

Cylindrical rubber fender – also similar to D-type and square type. Vessels come in direct contact with the rubber body and absorbs berthing energy by deformation of the rubber, it is necessary to pay particular attention to deterioration by external force.

Most Common Forms of Marine Fender Deterioration

Rubber marine fenders has different deterioration modes depending on the type as follows.

V-type rubber fender

Rubber body: Drops, tears, permanent deformation, missing rubber, cracks, chipping, separation, wear, ozone cracks, cuts, burns, bolt hole damage

Accessories (fixings): loose, bent, missing, cut, corrosion

Rubber fender with panel

Rubber body: tears, permanent deformation, cracks, separation, ozone cracks, burns, bolt hole damage,

Panel: deformation, corrosion,

Fixing: loose, bent, missing, cut, corrosion

Support: bent, cut, corrosion

Resin pad: wear, abrasion, cut, missing, burn

Pneumatic fender

Rubber body: cracks, chipping, separation, wear, ozone cracks, tears, burns, bolt hole damage

Air inlet valve: damage, corrosion

Body attachment: malfunction, corrosion

Net: corrosion, cuts, cracking, wear, burns

Mooring attachment: fender panel, support and resin pad: corrosion, etc.

Cylindrical fender

Rubber body: drops, cracks, missing rubber, tears, chipping, wear, ozone cracks, burns

Supports: bent, cut, corrosion

Inspection and Diagnosis

Detection and monitoring of damages and deterioration among rubber fenders at work is equally necessary to the design and material selection phase. This is to ensure that these port & harbor utilities are performing as designed for a long period of time and unfavorable circumstances due to failure are avoided. Frequency of mandatory inspection are the following.

Initial check – upon installation, assessment of the condition of the rubber fenders as unit and as a system should be carried out. Individual checks followed by commissioning through trial berthing can be the most ideal sequence of the test.
Daily check - routine inspection to assess the deterioration of the marine fenders on daily basis. The top priority of daily check is to detect any type and extent of damage and occurring deterioration.
Periodic check - periodic checks and diagnoses are conducted regularly to determine the progress of deterioration among rubber fenders. Periodic checks and diagnoses should be carried out systematically and continuously based on a pre-engineered inspection plan to evaluate the effectiveness of corrective measures in used and to be able to plan ahead in case of possible major troubleshooting.
Occasional check - occasional checks and diagnoses are conducted to confirm the damage of fenders when deterioration is recognized and in the events of unusual port incidents such as fire, uncontrolled berthing, and excessive vessel motion caused by wind storm, earthquake, tsunami, etc.

Counter-measures

All kinds of rubber fenders eventually suffer deterioration over a period of time due to ageing and the accumulation of impacts they have sustained. Preventive measures against deterioration must be taken about once or twice during the service period of a facility. Maintaining the working quality of rubber fenders is critical because a decrease in the number and function of rubber fenders can cause suspension of mooring operations resulting to losses.

With regard to the rubber body, it is common to most types to carry out replacement as a post-measure because preventive measures are difficult or not economical. However, in the case of pneumatic fenders, checking air pressure, repair, and reinforcement of the rubber body are practical maintenance measures.

In addition to unit replacement, measures for rubber fenders may include repair, repositioning, or restriction of use if possible. Appropriate measures can be taken from various viewpoints, such as deterioration status of rubber fenders, importance of facilities, and economic efficiency.

Action	Description of Corrective Action
Removal	This happens when fender is no longer needed
Replacement	This is done when preventive maintenance measures such as repair is difficult or not economical. Wise scheduling of replacement operation must be observed if suspension of port operations is not possible
Repair	This is advised when the performance and durability of the fender can be restored to a certain acceptable level. Generally, it is difficult to recover the function of a rubber body by repair or reinforcement, but for pneumatic fenders, repair or reinforcement is highly recommended provided that technical knowledge is present
Re-positioning	Switch the positions of frequently used rubber fenders with less frequently used rubber fenders. If practical, fenders can also be shuffled in a manner that intact or strong parts of the fenders are oriented to absorb greater impacts. However, for partial failure, adjusting fenders’ position may be possible but it is necessary to consider possible safety consequences
Service Restriction	Modification of conditions such as positioning of vessels in the dock, berthing speed and angle to moderate the severity of impacts, etc. These solutions require technical knowledge and proper consultation to all concerned. This can be used as an emergency or temporary solution depending on the circumstances at hand

In need of Professional Assistance?

ESC has strategic partnerships with PIANC registered manufacturers with over 20 years of experience delivering marine fender system solution worldwide.

Our marine rubber fenders has varieties in over 50 profiles, 5 rubber grades, and types such as the Cone Fender, Cell Fender, Element Fender, Arch Fender, Cylindrical Fender, Square Fender, Pneumatic Fender, and Foam Filled Fender.