【正文】 ts. The rapid accumulation in the delta always makes the river course to be diverted frequently. The abandoned delta would be eroded and retreated rapidly after diversion because the lack of supply. The gradient of the coastal slope in the delta is very gentle, the water depth is only 10m in the place about 10km apart from the coastal bank. A few of kilometerswide tidal flat would be exposed during ebb tide that makes us work on the tidal flat conveniently. The sediments on the tidal flat are mainly posed of fine sands, silt and clay. With the development of economic construction, various kinds of modernized traffic facility, is it pay to set up such as expressway , city, overpass function blown strengthen day by day in munications and transportation, the development of and the munications and transportation has caused the rapid rising of the traffic accident, traffic Safe and own through being a great world difficult problem The rigidity guardrail is offended the guardrail form not basically out of shape by the automobile, generally point the concept of adopting safe appearance of guardrail of modes in Chinese operatic music of concrete wall of concrete guardrail , through the different sides of slope of appearance mainly, make the automobile moderate , it is high to climb, change direction, last making not colliding kinds of guardrail angle smaller than 100 car not mediumsized making a change effective to, make automobile receive lighter damage, as angle of colliding, collide when relatively heavy speed having, the automobile damages seriously. According to rigidity with can divide into flexible guardrail , semirigid guardrail and rigidity guardrail safe form of guardrail. 1)The flexible guardrail generally points the cable guardrail , is one kind with structure that fixes of many roots on the pillar of cable of exerting prestressing force, totally relying on the stress of drawing of the cable to resist the vehicle and collide, the form is beautiful , not oppressing the sense while going, but the sight leads worse, the fabrication cost is relatively high, do not generally use. 2)The semirigid guardrail generally points the roof beam type guardrail , is a kind of roof beam type structure fixed with the pillar , depend on the guardrail crooked and out of shape and a pulling force resist the collision of the vehicle. There are a lot of kinds of the roof beam type guardrail , use the most extensive one to be the roof beam guardrail of the wave form . Have certain rigidity and toughness, easy to change after damaging, can lead the sight , the appearance is beautiful . 3)The rigidity guardrail generally points the cement concrete wall type guardrail , is a kind of concrete wall type structure of cement with certain section form , rely on the automobile to climb high , out of shape and rubing to absorb the energy of colliding . The guardrail security high, can prevent two accident effectively, itself difficult to damage, the maintenance cost is low, but have sense of oppressing to go to the vehicle, it is relatively serious to damage the vehicle. Security guardrail of expressway should prevent highspeed vehicle that go from exceed outlet, pass through central authorities is it is it is it to lane , can lead the driver39。s sight correctly to intrude upon to take to separate, make the vehicle get back to normal travel direction, and it is minimum to reduce malignant degree of the accident to. In a word, highspeed highway safety guardrail reduce traffic accident and reduce accident malignant effective measure of degree, but in shouldn39。s subjective judgement of such factors as class of highway , volume of traffic , vehicle making up and way side characteristic ,etc.. The most ideal guardrail form is that meet function39。 The concrete guardrail is suitable for very dangerous stepping such highway sections as the river bridge , cliff ,etc.。s stopping safely, make the vehicle change travel direction, avoid the department and take advantage of personnel39。 Meanwhile , is it get off vehicle get out under partial toing the breast board , or break the guardrail to defend。 3)While colliding , the damage to the passenger is the minimum degree: 4)Can lead the sight of the persons who drive . Can be found out from abovementioned functions, the guardrail must have suitable intensity of mechanics and collision in order to keep out the vehicle of rigidity , prevent the vehicle from crossing outside of outlet (the bridge ): Meanwhile, rigidity of guardrail can too heavy, can is it injure or lighten the degree of injuring to protect passenger from better. Real car full size is it is it offend with actual automobile guardrail is it imitate a kind of research approach of traffic accident to e to test to bump into. It can get automobile sport orbit and sport posture in the course of striking , such true believable technical parameters as the number value of shock power ,etc. of deformation and damage characteristic and colliding of the automobile and guardrail , thus offered the scientific basis for the dependability of other research approach ine results of design and verification of the safe and reliable guardrail structure. Now, various countries bump into the test of the real car of the system to regard as the basic prerequisite studied to the guardrail . Because the way side guardrail itself is a barrier , in a situation that the condition is permitted, the side guardrail of the way should be set up as much as possible and far away from the runway. So, the vehicle which deviates from the runway can perhaps is it answer to sail in the runway again having no accidents most heavy . Way side object exceed from runway edge sure to after worthing , take as the barrier , driver can because reducing speed last position. This distance is called and lea