Pile driver feet

An engineer will need to evaluate the soil and determine next steps. The solution to handling pile obstructions varies based on the depth of the obstruction.

The obstruction may reveal contaminated soil. If you encounter shallow obstructions within three feet of working grade, you can likely just remove it without significant impact to the surrounding soil.

Excavations are often not a viable solution where the obstructions are located beyond three feet or below the water table. In this situation, pre-drilling of pile locations can be employed. Deep pile obstructions may require an engineer to provide a remedial design.

Deep obstructions can reduce calculated bearing capacity. In this case, additional piles may be needed. Concrete piles are subject to various kinds of cracking. The direction, location, and severity of the cracks provide clues to the cause. Common problems with concrete piles and solutions include:. Where easy pile driving causes partial horizontal cracks in a concrete pile, check the hammer-pile alignment. Another possible cause is a combined tension and bending that is too high.

Where easy pile driving causes complete horizontal cracks in a concrete pile, calculated tension stresses may be off. If the tension stresses are too high, add cushioning or reduce the length of the hammer stroke.

If too low, it may be related to poor hammer performance. Complete horizontal cracks during hard driving require you to calculate tension stresses along the length of the pile.

If they are high, you may need a heavier ram. If too low, quakes are likely higher than expected. Using fiber optic sensors for pile monitoring allow you to measure stresses along the entire length of the pile during driving.

This provides greater accuracy as compared to standard monitoring. Note that cracks discovered early may be repaired with epoxy. Otherwise, they may end up in the pile heap. When there is spalling chipping or crumbling near the pile head, you will need to determine pile head stress for the blow count observed as compared to allowable stresses.

One cause for damage near the head of a concrete pile is insufficient pile cushioning. Adding pile cushioning is the solution to high stress. However, if your calculations indicate low stress, there are several potential causes. These include hammer performance and alignment issues, as well as poor pile quality. There are several things that can cause a steel pile head to deform or the head of a timber pile to split or splinter.

These include:. You can use a metal point or boot to protect the timber pile. Use them with banding near the top of the pile to prevent splitting. If you are still having an issue, calculate the stress on the pile head. Reduce the hammer stroke for low blow counts; increase for high blow counts. However, you may need to choose a different hammer — even a different pile type. Sometimes the pile driving hammer is the cause of problems.

In this case, ram friction may be the cause. If the observed blow count is less than calculated, soil resistance is likely lower than originally estimated.

If they are similar, use lower combustion pressure to align the hammer stroke. When using a wave analysis software program to predict pile behavior, you may run into data issues.

If the specific hammer you are using is not listed when you are entering wave analysis data, use a hammer of the same type. It should have a similar energy rating and ram weight. You will need to modify its data to fit the application. In some cases, there is no hammer that matches the driving stress and resistance limits. It may be that the calculated stresses and blow counts are too high. One option is to increase material strength — or make design changes.

Perform restrike or static load testing to confirm capacity. Pile driving sounds simple — hammer columns into the ground. But it is a complex process that requires extensive testing and accurate calculation. Selecting the right pile material and equipment for the soil and load capacity depends upon it.

There are several problems that can arise in the field. Preparation and contingency planning are the key to keeping a pile driving project on track and on budget. Volume 37 Issue 6. Volume 37 Issue 5. Volume 37 Issue 4. Volume 37 Issue 3. Volume 37 Issue 2. Volume 37 Issue 1. Volume 36 Issue 6.

She cinches in the hold but Sleeperkid refuses to give up. She releases him, trying to yank him to his feet, but he fires a hard punch into her belly, doubling her over. Sleeperkid goes on the attack, hauling Stephanie into the air and dropping her with a brutal pile-driver, laying her out cold on the mat.

A stomp to the back brings her around and he immediately scoops her up into a tombstone pile-driver, knocking her out again. He begins to count out a pinfall then thinks better of it, instead yanking Stephanie up to her knees and then slamming her head down to the mat, leaving her sprawling.

She grunts and struggles, as he rakes her across the eyes, then clubs her down to the mat He then pulls her to her feet, slamming her up into the wall before firing a series of belly punches into her exposed tummy, following up with cruel knee lifts that leave Stephanie gasping for air. A few shots to the head leave her slumping to the ground before he flips her with a snap mare, then settles in for a devastating leg scissors than has Stephanie wailing in pain.

Not yet finished, Sleeperkid hauls Stephanie to her knees, prying her arms behind her in a double arm bar of his own. Not satisfied with her whimpering, Sleeperkid leans back, hooking his legs around her arms for added pressure.

Quickly transitioning to a body scissors, he presses the attack, as Stephanie struggles to pry herself out of his grip. While the dynamic formula was used extensively in the past, when construction projects began to use concrete and steel pipes, it lost its utility.

The dynamic formula fails to take into account the driving system and the soil as it interacts with the pile. In addition, it models the pile as one rigid mass. As a result, use of the dynamic formula with concrete piles led to tension cracking. The wave equation — or stress-wave theory — addressed many of these issues. Australian David Victor Isaacs studied the use of the dynamic formula with concrete piles, and developed a mathematical model that took into account the successive transmission and reflection of waves.

In doing so, he could account for the stresses and displacements of the pile as it was driven. This formula also considers factors such as tension stresses in concrete piles, the effect of ram weight, and the impact of hammer cushion stiffness and drive cap weight. The study led to the development of a series of charts, which could then be used to estimate pile stresses and resistance for concrete piles. The study also addressed a number of technical issues that are still of interest to this day, such as instrumentation and data collection on stresses and forces in piles, the effect of the hammer cushion on the generation and effect of the pile stress wave, the relationship of ram weight to pile weight and cross section, and drop tower testing on cushion material to determine cushion stiffness.

Smith of the Raymond Concrete Pile Company developed a numerical method to model stress waves in piles and pile behavior. Beyond the dynamic formula, field monitoring techniques can also be used to understand pile dynamics. Geotechnical engineering principles that account for the uncertainty created by the use of soil and rock advanced the formulas used for pile-driving.

Initially, the blow count of the hammer per foot was used as a way to determine the capacity of the pile. Later, the stress wave theory was used to compare the pile force and velocity at a given time. Using this method, the static and dynamic soil resistance components could be separated. These types of hammers had two distinct advantages over other pile-driving methods.

First, they could operate without an external power source. Second, they were typically lighter than other hammers yet had comparable striking energy. The majority of diesel hammers manufactured today are the tubular, air-cooled type.

However, rod-type diesel hammers and water-cooled diesel hammers are used in some applications. However, the combustion chamber is hidden as the air is compressed and the duel is injected. The chamber is then exposed as the ram is thrown upwards from the combustion. Today, rod-type diesel hammers are used only for very small diesel hammers.

In contrast, water-cooled diesel hammers have a water tank that surrounds the combustion chamber. While this model allows for superior cooling capability, they are inconvenient to use. As a result, water-cooled diesel hammers are not popular in the construction industry. In the twentieth century, engineers in the former Soviet Union developed the first vibratory pile driver.

This hammer was powered by a 28 kilowatt electric motor, and had a dynamic force of kN. The VPM could drive pile pipes of millimeters in diameter into any type of soil other than rocky soils. It could also operate in two different frequencies. The VU It could also remove the plug from the pile while driving.

This hammer had a large center hole, which allowed it to remove soil without stopping the pile driver. This Soviet technology was licensed to the Japanese, who then developed their own vibratory hammers. Of note is the Uraga hammer, which involved the placement of an electric motor inside of each eccentric.

This machine differs from modern vibratory hammers in a number of ways. First, it used steel coils springs to provide dampening for the crane boom and hook; modern machines typically use rubber springs. Today, most machines mount the eccentrics from the front to the back of the case and drive them directly or through a speed-changing pinion gear.

Over time, Americans have developed a unique type of vibratory hammer with slim throat hammers for sheet pile driving, hydraulic drive, and high power engines, pumps and motors. The first impact-vibration hammer was built in the Soviet Union in This type of hammer involves a vibratory pile driver that imparts both vibrations and impacts while driving the pile.

The initial impact-vibration hammer was welded to the top of a metallic tube, and the hammer then drove the rube into a variety of soils. The results of driving piles in this way were compared against pile driving using only vibration.

The comparison of these two results demonstrated that impact-vibration driving is substantially more efficient in terms of maximum driving depth and pile installation speed. The impact-vibration hammer was first used in the construction of the Stalingrad now Volgograd power plant. Using these hammers, piles were driven into medium-firm sandstone to construction an anti-filtration wall under the dam.

The successful use of these hammers led to more widespread use, particularly in Europe. Unlike structural design, the design of pile foundation is not neat and precise.

The way that the piles and the surrounding soils interact adds a level of complexity to the process, with the introduction of piles into the soil typically altering the character of the soil. As a result, intense strains near the piles often occur.

Because soils are not homogenous and pile grouping and shaping can differ widely, pile foundation design and construction can be a challenging process. Instead of attempting to broadly characterize pile behavior, it makes more sense to work to understand the factors that influence the successful design of pile foundations. The foundation engineer must have an understanding of the following major factors:. An experienced geotechnical engineer should be consulted from the initial planning stages to final design and construction.

This engineer can assist in selecting the pile type, estimating pile length, and choosing the best method to determine pile capacity. To successfully translate the pile design into construction, the engineers must rate the requirements of the static analysis methods, the dynamic methods of field installation and construction control.