探头参数（圆锥净截面面积比）
系数α [-] 表示圆锥净截面面积比，由试验校验测量得到，用于消除侧壁和锥头的不完全吻合带来的不利影响。该系数的常见取值范围为0.7至0.85。
锥头和侧壁连接处不完全吻合的影响（来源：[6], Figure 20, pp. 22）
参考文献：
[1] EN ISO 22476-1: Geotechnical investigation and testing - Field testing. Part 1: Electrical cone and piezocone penetration test, 2013.
[2] EN ISO 22476-3: Geotechnical investigation and testing - Field testing. Part 3: Standard penetration test, 2005.
[3] EN ISO 22476-4: Geotechnical investigation and testing - Field testing. Part 4: Menard pressuremeter test, 2005.
[4] EN ISO 22476-12: Geotechnical investigation and testing - Field testing. Part 12: Mechanical cone penetration test (CPTM), 2009.
[5] Robertson, P. K.: Interpretation of Cone Penetration Tests – a unified approach. Canadian Geotechnical Journal, 2009, No. 46, pp. 1337 – 1355.
[6] Robertson, P. K. and Cabal, K. L.: Guide to Cone Penetration Testing for Geotechnical Engineering. Gregg Drilling & Testing, Inc., USA, 6th edition, 2014, 133 p.