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首页> 外文会议>Western Dredging Association Twenty-Second Technical Conference, Thirty-Fourth Texas Aamp;M Dredging Seminar, and Special Permanent International Association of Navigational Congresses Session, Jun 12-15, 2002, Denver, Colorado >THE EXISTENCE OF KINEMATIC WEDGES AT LARGE CUTTING ANGLES
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THE EXISTENCE OF KINEMATIC WEDGES AT LARGE CUTTING ANGLES

机译：大切削角时运动楔的存在

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In the last decennia extensive research has been carried out into the cutting of water saturated sand. In the cutting of water-saturated sand, the phenomenon of dilatation plays an important role. In fact the effects of gravity, inertia, cohesion and adhesion can be neglected at cutting speeds in the range of 0.5 ― 10 m/s. In the cutting equations, as published by Miedema, there is a division by the sine of the sum of the blade angle, the shear angle, the angle of internal friction and the soil/interface friction angle. When the sum of these angle approaches 180°, a division by zero is the result, resulting in infinite cutting forces. This may occur for example for α=80°, β=30°, φ=40° and δ=30°. When this sum is greater then 180 degrees, the cutting forces become negative. It is obvious that this cannot be the case in reality and that nature will look for another cutting mechanism. Hettiaratchi and Reece, 1975 found a mechanism which they called boundary wedges for dry soil. At large cutting angles a triangular wedge will exist in front of the blade, not moving relative to the blade. This wedge acts as a blade with a smaller blade angle. In fact, this reduces the sum of the 4 angles mentioned before to a value much smaller than 180°. The existence of a dead zone (wedge) in front of the blade when cutting at large cutting angles will affect the value and distribution of vacuum water pressure on the interface. He, 1998 , proved experimentally that also in water saturated sand at large cutting angles a wedge will occur. Although the number of experiments published is limited, his research is valuable as a starting point to predict the shape of the wedge At small cutting angles the cutting forces are determined by the horizontal and vertical force equilibrium equations of the sand cut in front of the blade. These equations contain 3 unknowns, so a third equation/condition had to be found. The principle of minimum energy is used as a third condition to solve the 3 unknowns. This has proved to give very satisfactory results finding the shear angle and the horizontal and vertical cutting forces at small cutting angles. At large cutting angles, a 4th unknown exists, the wedge angle or virtual blade angle. This means that a 4th equation/condition must be found in order to determine the wedge angle. There are 3 possible conditions that can be used: The principle of minimum energy, The circle of Mohr, The equilibrium of moments of the wedge. These methods are discussed and the choice made is explained.
机译：在上个十年中，已经对饱和水砂的切割进行了广泛的研究。在切割含水饱和砂时，膨胀现象起着重要作用。实际上，在切割速度为0.5〜10 m / s的范围内，重力，惯性，内聚力和附着力的影响可以忽略。在由Miedema出版的切削方程中，刀片角度，剪切角度，内摩擦角和土壤/界面摩擦角之和除以正弦值。当这些角度的总和接近180°时，结果将被零除，从而导致无限大的切削力。例如，对于α= 80°，β= 30°，Φ= 40°和δ= 30°，这可能发生。当此总和大于180度时，切削力将变为负值。显然，事实并非如此，大自然将寻找另一种切割机制。赫蒂亚拉奇（Hettiaratchi）和里斯（Reece），1975年发现了一种机制，他们称干土壤为边界楔块。在大切削角度下，在刀片前会存在一个三角形楔形，不会相对于刀片移动。该楔形物用作具有较小叶片角的叶片。实际上，这将前面提到的4个角度之和减小到远小于180°的值。当以大角度切割时，刀片前存在死区（楔形区）将影响界面上真空水压的值和分布。他，1998年，通过实验证明，在大切削角度的水中饱和砂土中也会产生楔形。尽管发表的实验数量有限，但他的研究作为预测楔形形状的起点是有价值的。在较小的切割角度下，切割力由在刀片前切割的水平和垂直力平衡方程确定。这些方程式包含3个未知数，因此必须找到第三个方程式/条件。最小能量原理被用作解决这三个未知数的第三条件。事实证明，在较小的切削角度下找到剪切角以及水平和垂直切削力，可以提供非常令人满意的结果。在大切削角度下，存在第四个未知数，即楔角或虚拟刀片角。这意味着必须找到第四个方程/条件才能确定楔角。可以使用3种可能的条件：最小能量原理，莫尔圆，楔形矩的平衡。讨论了这些方法并说明了选择方法。

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