共查询到20条相似文献,搜索用时 62 毫秒
1.
钻杆式水压致裂原地应力测试系统的柔性会影响最大水平主应力的计算精度。利用空心岩柱液压致裂试验获得的岩石抗拉强度来取代重张压力计算最大水平主应力是降低钻杆式测试系统柔性的负面影响的重要途径。在福建某隧道深度为65 m的钻孔内开展了8段的高质量水压致裂原地应力测试,随后利用钻孔所揭露的完整岩芯开展了17个岩样的空心岩柱液压致裂试验。利用空心岩柱液压致裂所得的抗拉强度平均值为8.40 MPa,与经典水压致裂法确定的岩体抗拉强度8.22 MPa接近。对于20 m的范围内8个测段的原地应力量值,最小水平主应力平均值为8.41 MPa,基于重张压力Pr的最大水平主应力平均值为16.70 MPa;基于空心岩柱抗拉强度的最大水平主应力量值平均值为16.88 MPa,两种方法获得的最大水平主应力平均值基本一致。最大最小水平主应力与垂直主应力之间的关系表现为σH > σV > σh,这种应力状态有利于区域走滑断层活动。通过对比分析可知,对于钻杆式水压致裂原地应力测试系统,当测试深度小且测试系统柔性小时,基于重张压力和基于空心岩柱抗拉强度得到的最大水平主应力量值差别不大,这说明基于空心岩柱的岩石抗拉强度完全可以用于水压致裂最大水平主应力的计算,同时基于微小系统柔性的水压致裂测试系统获得的现场岩体强度也是可靠的。 相似文献
2.
3.
4.
5.
青藏高原东北缘水压致裂地应力测量 总被引:11,自引:0,他引:11
在青藏高原东北缘首次采用水压致裂法进行了地应力测量,结果显示:在测量深度域内,青藏高原东北缘三个主应力之间的关系表现为σHmax〉σHmin〉σv,水平主应力占主导地位,现今地壳应力场的主压应力方向为NE-NEE,测量结果与地质事实较吻合。 相似文献
6.
7.
福建周宁水电站水压致裂地应力测量及其应用 总被引:2,自引:3,他引:2
周宁水电站在交通洞开挖过程中局部洞段发生了较强烈的岩爆。地下洞室和高压岔管、输水隧道设计及选择衬砌方式,需要查明原地应力状态。为此,采用水压致裂法在3个深钻孔中和岩爆部位进行了原位应力测量。结果表明,平面应力值随孔深增加呈线性增大;在岩爆和地下洞室附近,原位应力最大值为13~15 MPa,以水平挤压应力为主导,最大水平主应力方向为NW向。根据地应力测量资料和相关理论、判据分析认为:地下厂房长轴为NW向有利于围岩稳定;高压岔管和输水隧洞选用钢筋混凝土衬砌是可行的;发生局部岩爆,主要是由于隧道开挖围岩应力重新调整,在掌子面附近应力集中所致。 相似文献
8.
《地壳构造与地壳应力》2009,(2):27-38
1引言
1.国际岩石力学学会关于应力估算方法所给出的四个新建议主要包括以下四个部分:
第一部分:岩石应力估算策略;
第二部分:套芯应力解除法; 相似文献
9.
10.
利用最新研制的深孔水压致裂地应力测量设备在雪峰山2000 m科钻先导孔内开展了原地应力测量,在孔深170~2021 m范围内获得了16个测段的有效地应力测量数据,是国内首次利用水压致裂法获得的孔深超过2000 m深度的原地应力测量成果。测量结果表明,地应力随孔深增加而逐渐加大,对实测数据进行线性回归,得到最大和最小水平主应力随深度变化的关系分别为:SH=0.03328H+5.25408,Sh=0.0203H+4.5662,在孔深2021 m深度,其实测值分别为66.31 MPa和43.33 MPa。基于实测数据,结合钻孔成像测试和井温测试结果,对测点应力状态进行了综合分析。在170~800 m深度范围,三向主应力关系为SH > Sh > Sv,有利于逆断层活动;孔深1000~2021 m表现为SH > Sv > Sh,表明该区域深部应力结构属于走滑型。最大水平主应力方向为北西-北西西方向。基于实测地应力数据及莫尔-库伦破裂准则,对测区附近断层活动性进行了分析讨论,认为该区域断层处于稳定状态。 相似文献
11.
Wang Jing-tao 《岩土力学》1982,3(1):1-12
A new fracture mechanics approach for in-situ stress determination by hydra-fracturing is proposed. It improves the fracture mechanics method as presented by Abou-Sayed etc. (1978). The accuracy of determination of the maximum horizontal stress (σHmax) is considerably enhanced by replacing fracture toughness of rock, K1c, and preexisting crack length L in rock by a new parameter U(U=K1c/√2) . The reason is that K1c is related to crack length L when crack length is smaller than a critical value and to determine the length of preexisting crack in rock as accurate as possible is very difficult. In addition the parameter U can be directly measured through a simple hollow-cylinder burst test. Based on recent experimental tests of fracture toughness of rock the new parameter U appears to be a constant when crack lengths are smaller than a certain critical value . The parameter √2 U may be taken also as a tensile strength of rock which contains small randomly distributed preexisting cracks. 相似文献
12.
Investigation of a Limestone Pillar Failure Part 2: Stress History and Application of Fracture Mechanics Approach 总被引:1,自引:0,他引:1
Summary Observed pillar failure could not be explained by comparing pillar strength with stresses on the pillar induced by mining
activities. Instead, the effects of the combined stress history of strata and pillar on the deformational response of rock
mass and rock were assessed. Application of the principles of fracture mechanics, i.e., extension strain and strain energy
release rate criteria gave a reasonable explanation for the observed pillar behavior. The derivation of the required fracture
mechanics parameters from laboratory tests is described, and the necessity of an interdisciplinary approach to rock engineering,
i.e., the use of historical geology, engineering geology, mining engineering and rock mechanics, is mandated. 相似文献
13.
Experimental Study on Stress Transfer and Fracture Law During the Hydraulic Fracturing of Coal Seams
Geotechnical and Geological Engineering - Hydraulic fracturing is a key technology for increasing the permeability of coal seams and improving the extraction effect of coalbed methane. Exploring... 相似文献
14.
为确定水平井裂缝破裂点位置,指导射孔位置的优选,建立了综合考虑多条人工裂缝诱导应力、井筒内压、原地应力、热应力、压裂液渗流效应和射孔联合作用下的水平井分段压裂应力场模型,模型重点考虑了先压开裂缝产生的诱导应力场影响,更符合水平井分段压裂的实际特点,在此基础上结合岩石破裂准则从降低破裂压力角度形成了破裂点优化方法。研究结果表明先压开裂缝产生的诱导应力场影响使得水平井筒周围应力场更为复杂,研究裂缝起裂问题时必须考虑这一因素。对川西水平井分段压裂的破裂点进行了优化,压裂后输气求产,实际破裂压力梯度低于邻井同层的破裂压力梯度,大大降低了施工风险。该破裂点优化方法对水平井分段压裂优化设计有一定的指导意义。 相似文献
15.
冰工程对于断裂力学是一个相对较新的应用领域.对不同工程领域中广泛存在的涉冰断裂力学问题进行了列举归纳,然后从冰的自然特性诸方面论证了冰工程分析中引入断裂力学方法的必要性及其适用性,最后综述了主要的研究成果和进展. 相似文献
16.
The Time-Dependent Reduction of Sliding Cohesion due to Rock Bridges Along Discontinuities: A Fracture Mechanics Approach 总被引:1,自引:3,他引:1
J. Kemeny 《Rock Mechanics and Rock Engineering》2003,36(1):27-38
Summary
In this paper, a fracture mechanics model is developed to illustrate the importance of time-dependence for brittle fractured
rock. In particular a model is developed for the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion
is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics
model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function
of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found
to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value
that results in slope instability. A second example is given where variations in some of the material parameters are assumed.
A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability
of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples
show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for
relatively short-term rock structures.
Received November 5, 2001; accepted July 24, 2002; Published online November 19, 2002 相似文献
17.
We develop a new analytical model, called OpenT, that solves the elasticity problem of a hydraulic fracture (HF) contact with a pre-existing discontinuity natural fracture (NF) and the condition for HF re-initiation at the NF. The model also accounts for fluid penetration into the permeable NFs. For any angle of fracture intersection, the elastic problem of a blunted dislocation discontinuity is solved for the opening and sliding generated at the discontinuity. The sites and orientations of a new tensile crack nucleation are determined based on a mixed stress- and energy-criterion. In the case of tilted fracture intersection, the finite offset of the new crack initiation point along the discontinuity is computed. We show that aside from known controlling parameters such stress contrast, cohesional and frictional properties of the NFs and angle of intersection, the fluid injection parameters such as the injection rate and the fluid viscosity are of first-order in the crossing behavior. The model is compared to three independent laboratory experiments, analytical criteria of Blanton, extended Renshaw?Pollard, as well as fully coupled numerical simulations. The relative computational efficiency of OpenT model (compared to the numerical models) makes the model attractive for implementation in modern engineering tools simulating hydraulic fracture propagation in naturally fractured environments. 相似文献
18.
A New Method for In-situ Non-contact Roughness Measurement of Large Rock Fracture Surfaces 总被引:2,自引:1,他引:2
Summary
This paper presents a new method for in-situ non-contact measurements of fracture roughness by using a total station (TS).
The TS is a non-reflector geodetic instrument usually used for measuring control points in surveying and mapping. By using
a special-developed program, the TS can be used as a point-sensor laser scanner to scan a defined area of the fracture surface
automatically, in field or in laboratory, at a distance away from the target surface. A large fracture surface can be automatically
scanned with a constant interval of the sampling points, both within a defined area or along a cross-section of the exposed
rock face. To quantify fracture roughness at different scales and obtain different densities of the scanned points, the point
interval can be selected with the minimum interval of 1 mm. A local Cartesian co-ordinate system needs to be established first
by the TS in front of the target rock face to define the true North or link the measurements to a known spatial co-ordinate
system for both quantitative and spatial analysis of fracture roughness. To validate the method, fracture roughness data recorded
with a non-reflector TS was compared with the data captured by a high-accuracy 3D-laser scanner. Results of this study revealed
that both primary roughness and waviness of fracture surfaces can be quantified by the TS in the same accuracy level as that
of the high accuracy laser scanner. Roughness of a natural fracture surface can be sampled without physical contact in a maximum
distance of tens of meters from the rock faces.
Received May 24, 2001; accepted July 24, 2002; Published online November 19, 2002 相似文献
19.
S. Seifollahi P. A. Dowd C. Xu A. Y. Fadakar 《Rock Mechanics and Rock Engineering》2014,47(4):1225-1235
Fracture network modelling plays an important role in many application areas in which the behaviour of a rock mass is of interest. These areas include mining, civil, petroleum, water and environmental engineering and geothermal systems modelling. The aim is to model the fractured rock to assess fluid flow or the stability of rock blocks. One important step in fracture network modelling is to estimate the number of fractures and the properties of individual fractures such as their size and orientation. Due to the lack of data and the complexity of the problem, there are significant uncertainties associated with fracture network modelling in practice. Our primary interest is the modelling of fracture networks in geothermal systems and, in this paper, we propose a general stochastic approach to fracture network modelling for this application. We focus on using the seismic point cloud detected during the fracture stimulation of a hot dry rock reservoir to create an enhanced geothermal system; these seismic points are the conditioning data in the modelling process. The seismic points can be used to estimate the geographical extent of the reservoir, the amount of fracturing and the detailed geometries of fractures within the reservoir. The objective is to determine a fracture model from the conditioning data by minimizing the sum of the distances of the points from the fitted fracture model. Fractures are represented as line segments connecting two points in two-dimensional applications or as ellipses in three-dimensional (3D) cases. The novelty of our model is twofold: (1) it comprises a comprehensive fracture modification scheme based on simulated annealing and (2) it introduces new spatial approaches, a goodness-of-fit measure for the fitted fracture model, a measure for fracture similarity and a clustering technique for proposing a locally optimal solution for fracture parameters. We use a simulated dataset to demonstrate the application of the proposed approach followed by a real 3D case study of the Habanero reservoir in the Cooper Basin, Australia. 相似文献