1)樁的單位面積承載力較高, 由于其屬擠土樁,樁打人后其周圍的土層被擠密,從而提高地基承載力;
2)樁身質(zhì)量易于保證和檢查;適用于水下施工;樁身砼的密度大,抗腐蝕性能強(qiáng);施工工效高;因其打入樁的施工工序較灌注樁簡單,工效也高;
3)預(yù)制樁單價較灌注樁高。預(yù)制樁的配筋是根據(jù)搬運、吊裝和壓人樁時的應(yīng)力設(shè)計的,遠(yuǎn)超過正常工作荷載的要求,用鋼量大,接樁時,還需增加相關(guān)費用;
4)錘擊和振動法下沉的預(yù)制樁施工時,震動噪音大,影響周圍環(huán)境,不宜在城市建筑物密集的地區(qū)使用,一般需改為靜壓樁機(jī)進(jìn)行施工;
5)預(yù)制方樁是擠土樁,施工時易引起周圍地面隆起,有時還會引起已就位鄰樁上??;
6)受起吊設(shè)備能力的限制,單節(jié)樁的長度不能過長,一般為10余米,長樁需接樁時,接頭處形成薄弱環(huán)節(jié),如不能確保全樁長的垂直度,則將降低樁的承載能力,甚至還會在打樁時出現(xiàn)斷樁;
7)不易穿透較厚的堅硬地層,當(dāng)堅硬地層下仍存在需穿過的軟弱層時,則需輔以其他施工措施,如采用預(yù)鉆孔(常用的引孔方法)等。
1) the bearing capacity of the unit area of piles is higher, because of the soil compaction pile, the soil layer around the pile is compacted, thus improving the bearing capacity of the foundation.;
2) quality of pile body is easy to check and ensure; workover is suited for underwater applied; the density of the pile body concrete, strong corrosion resistance performance; high construction efficiency; because of its into the pile construction process than perfusion pile simple, work efficiency is high;
3) the unit price of precast piles is higher than the pouring piles. The reinforcement of the precast piles is designed according to the stress of carrying, hoisting and piling, far more than the normal working load, and it need to increase the relevant expenses when the steel is large and the pile is connected.;
4) hammer and method of vibration sinking precast pile construction, the vibration noise, affecting the surrounding environment, should not be used in city building dense areas, it generally takes change for static pressure pile machine construction;
5) precast piles are crowded piles, which can easily lead to uplift of surrounding ground, sometimes caused by the uplift of piles.;
6) is limited by the ability of lifting equipment, single section pile length should not be too long, generally more than 10 meters, long pile for pile splicing and joints formed weak link, if not to ensure the whole pile verticality, it will reduce the bearing capacity of the pile, even at the time of driving appear broken pile;
7) it is hard to penetrate thick hard strata, and when the hard strata still exist in the weak layer, then need to be supplemented with other construction measures, such as the use of pre drilling (commonly cited hole method), etc..