Tunnel Face Stability & New CPT Applications
Tunnel Face Stability & New CPT Applications
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发表时间：
2001-09
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通讯作者：
W. Broere
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作者：
W. Broere
几乎所有在软土中修建的隧道都遇到了隧道掌子面稳定性的问题。在一些情况下，这些问题导致了钻孔过程的长期停滞。更好地了解工作面稳定性和隧道掘进机周围的土壤条件可以降低掘进过程中的风险，并避免成本增加和延误。在软土中开挖隧道时，为了避免稳定性问题，掌子面处的支撑压力应保持在最小和最大支撑压力之间。现有的工作面稳定性模型，但是，不包括钻孔过程的影响。开挖过程可能导致隧道掘进机前方产生超孔隙水压力，从而降低工作面的稳定性。这些超孔隙水压力已被纳入一个新的稳定性模型，也可以处理土壤的异质性。这导致所需支撑压力的更可靠的计算。此外，一些新的应用锥贯入试验已被调查，看看是否可以获得有关土壤条件的额外信息。代替传统的从土壤表面的垂直探测，也可以从隧道掘进机在水平方向上进行探测。从实验室调查和理论模型，它已被发现，测量略有依赖于测深方向。这些差异可以进行校正，以便将现有的（垂直）相关性也用于水平圆锥贯入试验。此外，为了获得关于砂层密度的信息，通过高速压电测深测量的超静孔隙水压力与常规压电测深获得的超静孔隙水压力进行了比较。虽然在实验室试验中发现了显著的差异，但与砂的密度没有建立可靠的关系。结果表明，在正常的测深速率下，在高速下也能可靠地获得其它常规测量值。
Nearly all tunnels bored in soft soils have encountered problems with the stability of the tunnel face. In several cases these problems led to an extended stand-still of the boring process. A better understanding of the face stability, and of the soil conditions around the tunnel boring machine, can reduce the risks during boring, and can avoid cost increases and delays. During the boring of tunnels in soft soils, the support pressure at the face should remain between a minimal and maximal support pressure, in order to avoid stability problems. Existing face stability models, however, do not incorporate the influence of the boring process. The excavation process may lead to excess pore pressures in front of the tunnel boring machine, which lower the stability of the face. These excess pore pressures have been incorporated in a new stability model, that can also deal with heterogeneity of the soil. This leads to a more reliable calculation of the required support pressure. Also, a number of new applications of the cone penetration test have been investigated, to see whether additional information about the soil conditions can be obtained. Instead of the traditional, vertical, sounding from the soil surface, a sounding can also be made from the tunnel boring machine in a horizontal direction. From laboratory investigations and theoretical models it has been found that the measurements depend slightly on the sounding direction. These differences can be corrected for, in order to use the existing (vertical) correlations also for horizontal cone penetration testing. Further, to gain information on the density ofsand layers, the excess pore pressures measured by a high-speed piezosounding have been compared to those obtained from regular piezosoundings. Although significant differences have been found in laboratory tests, no reliable relation with the density of the sand has been established. It has been shown that the other regular measurements can be reliably obtained at high speed as well as at the normal sounding rates.