高山河谷地区地应力分布特征及对节理围岩工程稳定性的影响

发布时间：2018-05-06 04:41

本文选题：高山 + 河谷　；参考：《山东大学》2015年硕士论文

【摘要】：高山河谷地区具有特殊的地质地貌特征。复杂的地质构造作用和河谷表面长期受到的风化作用,使高山河谷地区原有的应力场重新分布和调整,形成了该地区现今特殊的地应力场分布。另外,由于河谷地区地质构造复杂,现代构造活动强烈,边坡岩体内节理裂隙发育。节理裂隙的存在,使岩体表现出很强的非均质性、不连续性和各向异性,影响岩体的强度和变形特性。在高山河谷地区进行地下工程,必然引起影响范围内岩体的变形,随之发生地应力的释放和调整,对节理围岩的稳定性产生影响。因而,针对修建于高山河谷地区的地下工程,需要结合地应力场的分布规律和节理岩体的力学特性来分析工程的稳定性。本文首先利用有限差分软件FLAC-3D对高山河谷地区地应力场的分布特征进行了研究。分别考虑了地形地貌、自重作用、构造应力、风化等因素对高山河谷地区地应力场的影响：(1)不同的山体坡度会对初始地应力的分布产生十分重要的影响。通过数值分析研究了当山体坡度不同时,在重力场条件下以及不同地应力侧压力系数时山体中水平向典型剖面中初始地应力的大小与分布的特点。得到了在水平方向上距坡体表面一定范围内存在坡面效应的结论,且此效应随山体坡地的增大以及水平向构造应力的增大而越发明显。并指出在此区域内修建地下工程时,不能简单的取其直接埋深算出的垂直向地应力作为该处的地应力值。(2)在第一步的基础上,考虑河流下切作用,建立呈“V”字型对称分布形式的不同坡度河谷模型,同时在河谷表面设置四层不同风化程度的分化带来模拟风化作用产生的卸荷作用,得到了在考虑风化作用下的河谷地区地应力分布的特征。将得到的结果与前人通过现场实测得到的地应力场的规律进行了对比,验证了河谷地区地应力场的“驼峰型”分布特征。同时将通过数值模拟得到的45°河谷在2.25倍水平向地应力作用下的地应力场与二滩水电站现场实测的地应力场相对比,结果十分吻合,验证了数值计算结果的正确性。其次,详细介绍了如何利用模型试验和数值方法研究节理岩体的强度和变形特性。通过对包含有30°、45°、60°三种裂隙倾角的节理试件和完整试件进行单轴压缩室内试验,研究了节理的存在对岩体的强度及变形特性的影响；结合现场调查的岩体节理裂隙分布规律,利用蒙特卡洛方法,生成了随机节理数值试件,并利用数值加载试验研究了裂隙随机分布对节理岩体强度的影响,研究了岩体特征单元体的REV尺寸和等效力学参数。第三,提出了一种基于二次型包络线的岩体强度准则。对满足REV尺寸的数值试件模拟不同围压下的加载试验,利用试验得到的应力应变曲线求解试件的二次包络线,并以此作为节理岩体的强度准则,为工程算例的计算奠定了基础。最后,将通过模型试验和岩体特征单元体得到的节理岩体力学参数与高山河谷地区地应力场的分布特征将结合,研究了高山河谷地区地应力场的分布特征对节理围岩工程稳定性的影响。在V字型河谷地区和高山地区山体中不同高程距坡脚3个不同距离分别开挖1个洞室,采用了节理岩体的等效力学参数以及室内试验得到的岩体力学参数做数值分析,比较各方案洞室的围岩稳定性状况,得到以下结论：(1)水平向地应力的作用是影响节理围岩稳定性的重要因素。一般来说,随着水平向地应力作用的增大,洞室开挖后,塑性区体积会增大。不过当洞室处于山体深处时,垂直向成为最大主应力的方向,随着水平向地应力作用的增大,最大主应力和最小主应力的差值会减小,这对洞室开挖后围岩的稳定性有利,塑性区会随着水平向地应力作用的增大而减小。(2)山体的坡面效应是影响节理围岩稳定性的重要因素。开挖洞室距坡脚越近,塑性区体积越大,对节理围岩稳定性越不利。同时也说明了地应力的计算常规的做法——一律取其上部岩体的直接埋深h作为该点初始垂直向地应力的计算方法——在山体内接近坡面一定距离内是不妥的。(3)在河谷地区,洞室开挖应尽量避开应力峰值区和应力升高区。应力升高区通常为风化区,该区域内尽管应力水平较低,但由于岩体受到外界的风化作用,岩体力学参数较低,不利于围岩稳定；而应力峰值区在同高程应力水平最高,最大主应力与最小主应力的差值也最大,对洞室开挖后围岩的稳定性十分不利；相反,在原岩应力区,最大主应力与最小主应力之间的差值较小,对洞室开挖后围岩稳定性有利。(4)在河谷地区,洞室开挖位置高程越低,对洞室围岩稳定性越不利。产生这一影响的原因在于河谷底部的高应力集中——即“高应力包”的存在。在0m高程,由于距离河谷底部较近,靠近坡脚处本身也可以看做是应力集中区域,因而应力水平较高,不利于围岩的稳定；随着高程的增加,受“高应力包”的影响也逐渐减小,应力水平也逐渐降低,因而洞室开挖后塑性区也逐渐减少。
[Abstract]:The high mountain valley area has special geological and geomorphic features. The complex geological structure and the long-term weathering effect of the valley surface make the original stress field redistributed and adjusted in the alpine valley area, forming a special distribution of the present stress field in this area. In addition, the modern tectonic activity is complicated because of the complex geological structure in the valley area. It is strong that the joints and cracks in the rock slope are developed. The existence of joint cracks causes rock mass to show strong heterogeneity, discontinuity and anisotropy, which affects the strength and deformation characteristics of rock mass. Underground engineering in the alpine valley area is bound to cause the deformation of rock mass within the affected area, and the stress release and adjustment will occur with it. The stability of the surrounding rock is affected. Therefore, for the underground engineering built in the alpine valley area, the stability of the engineering is analyzed in combination with the distribution of the stress field and the mechanical properties of the jointed rock mass. Firstly, the distribution characteristics of the geostress field in the alpine valley area are studied by using the finite difference software FLAC-3D. The influence of topography, gravity, tectonic stress, weathering and other factors on the geostress field in the alpine valley area: (1) the gradient of different mountain slopes will have a very important influence on the distribution of initial geostress. The characteristics of the size and distribution of the initial geostress in a typical profile in a mountain range, the conclusion is drawn that there is a slope effect in a certain range in a horizontal direction to the surface of the slope body, and the effect of this effect is more obvious with the increase of the hill slope and the increase of the horizontal tectonic stress. At the same time, the vertical crustal stress calculated directly by the direct buried depth can not be taken as the geostress value of the site. (2) on the basis of the first step, considering the river cutting action, a different slope Valley model is established in the form of "V" type symmetry distribution. At the same time, the differentiation of different weathering degrees of four layers on the valley surface brings simulated weathering effect. The distribution of ground stress in the valley area under the consideration of weathering is obtained. The results are compared with the law of the ground stress field measured by the predecessors, and the distribution characteristics of the "Hump type" in the ground stress field in the valley area are verified. At the same time, the 45 degree Valley in the river valley is obtained by numerical simulation. The ground stress field under the 2.25 times horizontal stress is compared with the in-situ stress field measured at the two beach hydropower station. The results are in good agreement, and the correctness of the numerical results is verified. Secondly, how to use the model test and numerical method to study the strength and deformation characteristics of jointed rock mass is described in detail. Through the inclusion of 30, 45, 60 degrees, it is described in detail. Three kinds of jointed joints and complete specimens were tested in a single axis compression test, and the influence of the existence of joints on the strength and deformation of rock mass was studied. The influence of the gap random distribution on the strength of jointed rock mass, the REV size and the equivalent mechanical parameters of the rock mass element are studied. Third, a rock mass strength criterion based on the two type envelope is proposed. The loading test under different confining pressure is simulated for the numerical specimen with the size of the REV, and the stress strain curve obtained by the test is used to solve the specimen. The two enveloping line is used as the strength criterion of the jointed rock mass, which lays the foundation for the calculation of the engineering example. Finally, the distribution characteristics of the stress field in the alpine valley area will be combined by the mechanical parameters of the jointed rock mass obtained by the model test and the characteristic element body of the rock mass, and the distribution characteristics of the geostress field in the alpine valley area are studied. The influence on the stability of the Jointed Surrounding Rock Engineering. 1 caverns were excavated at 3 different distances from the foot of different elevation in the V Valley and the mountain areas. The equivalent mechanical parameters of the jointed rock mass and the rock mechanics parameters obtained in the laboratory were numerically analyzed to compare the stability of the surrounding rock. The following conclusions are as follows: (1) the effect of horizontal stress on the ground stress is an important factor affecting the stability of the jointed rock. In general, the volume of the plastic zone will increase with the increase of the horizontal stress on the ground stress, but when the cavern is in the depth of the mountain, the vertical direction becomes the direction of the largest main stress, and the horizontal stress acts along with the horizontal stress. The difference between the maximum principal stress and the minimum principal stress will be reduced, which is beneficial to the stability of the surrounding rock after the excavation of the cavern, and the plastic zone will decrease with the increase of the horizontal stress on the ground. (2) the slope effect of the mountain is an important factor affecting the stability of the jointed rock. The more bad the rock stability is, it also illustrates the conventional method of calculating the stress. It is not appropriate to take the direct buried depth h of the upper rock mass as a calculation method of the initial vertical stress of this point - in a mountain near a certain distance to the slope. (3) in the Valley area, the cave excavation should try to avoid the peak stress zone and stress. The rising area is usually a weathering zone, although the stress level is low in this area, but because of the weathering of the rock mass, the mechanical parameters of rock mass are low and not favorable to the stability of the surrounding rock, and the peak stress zone is the same as the Gao Chengying force, and the difference between the maximum principal stress and the minimum main stress is also the most, and the surrounding rock after the excavation is excavated. On the contrary, the difference between the maximum principal stress and the minimum principal stress is smaller in the original rock stress area, and it is beneficial to the stability of the surrounding rock after the excavation of the cavern. (4) the lower the height of the excavation position in the valley, the more unfavorable to the stability of the surrounding rock. The cause of this effect lies in the high stress concentration at the bottom of the valley. - the existence of "high stress package". In the 0m elevation, as the distance from the bottom of the valley is closer to the bottom of the valley, the stress concentration area can also be seen as a stress concentration area, so the stress level is high and is not conducive to the stability of the surrounding rock. As the elevation increases, the influence of the "high stress package" decreases gradually, and the stress level is gradually reduced, thus caverns open. After digging, the plastic zone is also gradually reduced.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU452

【参考文献】